OM-20000041 Rev 1
OM-20000041 REV 1
MiLLennium GPSCard
Software Version 4.50
Command Descriptions Manual
GPSCard Products
NovAtel Inc.
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Table of Contents
TABLE OF CONTENTS
TABLE OF CONTENTS
Congratulations! ....................................................................................................................................... 11
Scope ........................................................................................................................................................ 11
Prerequisites ............................................................................................................................................. 11
1.1 Installation .......................................................................................................................................... 12
Graphical Interface ...................................................................................................................... 12
1.3 Differential Operation ........................................................................................................................15
1.4 RTK Mode ....................................................................................................................................... 17
System Initialization .................................................................................................................... 18
Monitoring Your RTK Output Data ............................................................................................ 20
Initialization - Rover Station ....................................................................................................... 21
2.1 General ...............................................................................................................................................23
Optional calculation of the checksum .......................................................................................... 24
2.2 Standard Command Tables ................................................................................................................ 25
2.3 WAAS ............................................................................................................................................. 29
2.3.1 WAAS GPSCard ................................................................................................................ 30
2.4 Special Data Input Commands ........................................................................................................ 30
2.4.1 Almanac Data ..................................................................................................................... 30
2.4.2 Differential Corrections Data ............................................................................................. 32
3.1 Output Logging .................................................................................................................................. 34
Binary Log Structure ................................................................................................................... 35
3.3 RTK .................................................................................................................................................... 36
3.7 WAAS ............................................................................................................................................. 42
3.7.1 WAAS GPSCard Logs .................................................................................................... 42
3.8 Pass-Through Logs .......................................................................................................................... 42
3.8.1 Command Syntax ............................................................................................................ 43
3.8.2 ASCII Log Structure ........................................................................................................ 43
3.8.3 Binary Log Structure ....................................................................................................... 44
RTCA Standard Logs .................................................................................................................. 46
4.2 RTCM-format Messages .................................................................................................................... 47
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RTCM Standard Logs ..................................................................................................................49
4.4 RINEX Format .................................................................................................................................56
The Control Segment ...................................................................................................................63
A.3 GPS Positioning .................................................................................................................................64
A.3.1 Differential Positioning ......................................................................................................66
A.3.2 Pseudorange Algorithms ....................................................................................................67
A.4 Carrier-Phase Algorithms ..................................................................................................................71
B.1 Multipath ............................................................................................................................................73
Why Does Multipath Occur? .......................................................................................................73
B.2 Hardware Solutions For Multipath Reduction ...................................................................................74
Antenna Designs ..........................................................................................................................75
NovAtel’s Internal Receiver Solutions for Multipath Reduction ................................................76
FIX HEIGHT ...............................................................................................................................97
FIX POSITION.............................................................................................................................98
FIX VELOCITY ..........................................................................................................................99
IONOMODEL WAAS ................................................................................................................103
LOCKOUT ...................................................................................................................................104
LOG ..............................................................................................................................................105
MAGVAR ....................................................................................................................................106
MESSAGES .................................................................................................................................108
POSAVE ......................................................................................................................................109
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RESET.......................................................................................................................................... 110
RESETHEALTH ......................................................................................................................... 111
RESETHEALTHALL .................................................................................................................111
RINEX.......................................................................................................................................... 112
RTCM16T ................................................................................................................................... 113
RTCMRULE ............................................................................................................................... 114
SAVEALMA ............................................................................................................................... 119
SAVECONFIG ............................................................................................................................ 120
SEND ...........................................................................................................................................121
SETDGPSID ................................................................................................................................ 123
SETHEALTH .............................................................................................................................. 124
SETL1OFFSET ........................................................................................................................... 125
UNASSIGN ................................................................................................................................. 129
UNASSIGNALL ......................................................................................................................... 129
UNDULATION ........................................................................................................................... 130
UNFIX ......................................................................................................................................... 131
UNLOCKOUT ............................................................................................................................ 131
UNLOG ....................................................................................................................................... 132
USERDATUM ............................................................................................................................ 133
VERSION..................................................................................................................................... 134
WAASCORRECTION WAAS ................................................................................................... 135
ALMA/B ...................................................................................................................................... 136
BSLA/B RTK ............................................................................................................................. 141
CDSA/B ....................................................................................................................................... 144
CLMA/B....................................................................................................................................... 149
CMR ............................................................................................................................................ 151
COM1A/B and COM2A/B .......................................................................................................... 152
ETSA/B ....................................................................................................................................... 155
GGAB...........................................................................................................................................158
GPALM ....................................................................................................................................... 159
GPGLL ........................................................................................................................................ 161
GPGRS ........................................................................................................................................ 162
GPGSA ........................................................................................................................................ 163
GPGSV ........................................................................................................................................ 165
GPRMB ....................................................................................................................................... 166
GPRMC ....................................................................................................................................... 167
GPVTG ........................................................................................................................................ 168
GPZDA ........................................................................................................................................ 169
GPZTG ........................................................................................................................................ 170
MKPA/B ...................................................................................................................................... 171
NAVA/B....................................................................................................................................... 173
POSA/B ....................................................................................................................................... 178
PRTKA/B RTK ........................................................................................................................... 179
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RTKA/B RTK .............................................................................................................................205
RTKOA/B RTK .........................................................................................................................207
VERA/B........................................................................................................................................219
WALA/B WAAS .........................................................................................................................222
WRCA/B ......................................................................................................................................224
E.1 RT-2 & RT-20 Performance ..............................................................................................................225
E.2 Performance Considerations ..............................................................................................................231
H.1 Distance ...........................................................................................................................................236
H.3 Temperature.....................................................................................................................................236
H.4 Weight .............................................................................................................................................236
H.5 Hexadecimal And Binary Equivalents ............................................................................................236
H.6 GPS Time of Week to Calendar Day (example) .............................................................................237
Type 1 Information Messages ..................................................................................................................238
Type 2 Information Messages ..................................................................................................................239
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FIGURES
A-1 NAVSTAR Satellite Orbit Arrangement ................................................................................................. 62
A-2 Illustration of GPSCard Height Measurements ........................................................................................ 64
A-3 Accuracy Versus Precision ....................................................................................................................... 65
A-4 Example of Differential Positioning ........................................................................................................ 66
A-5 Single Point Averaging ............................................................................................................................ 69
A-6 Typical Differential Configuration ........................................................................................................... 70
B-1 Illustration of GPS Signal Multipath ........................................................................................................ 73
B-2 Illustration of GPS Signal Multipath vs. Increased Antenna Height ....................................................... 75
B-3 Illustration of Quadrifilar vs. Microstrip Patch Antennae ........................................................................ 76
B-4 Comparison of Multipath Envelopes ........................................................................................................ 78
C-1 HELP Command Screen Display .............................................................................................................102
C-2 Appended Command Screen Display ......................................................................................................102
C-3 Illustration of Magnetic Variation & Correction ...................................................................................... 107
C-4 Using SEND Command ............................................................................................................................ 121
C-5 Illustration of SETNAV Parameters ........................................................................................................ 127
C-6 Illustration of Undulation ......................................................................................................................... 130
D-1 Example of Navigation Parameters .......................................................................................................... 175
D-2 The WGS84 ECEF Coordinate System ................................................................................................... 185
E-1 Typical RT-2 Horizontal Convergence - Static Mode ............................................................................. 227
E-2 Typical RT-2 Horizontal Convergence - Kinematic Mode ...................................................................... 227
E-3 RT-2 Accuracy Convergence ................................................................................................................... 228
E-4 Illustration of RT-2 Steady State Performance ........................................................................................ 228
E-5 Typical RT-20 Convergence - Static Mode ............................................................................................. 229
E-6 Typical RT-20 Convergence - Kinematic Mode ...................................................................................... 230
E-7 RT-20 Steady State Performance .............................................................................................................230
E-8 RT-20 Re-initialization Process ............................................................................................................... 232
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Table of Contents
TABLES
2-1
3-1
Commands By Function Table .................................................................................................................25
Logs By Function Table ...........................................................................................................................38
GPSCard Log Summary ...........................................................................................................................41
Positioning Modes ....................................................................................................................................45
C-1 Antenna LNA Power Configuration .........................................................................................................81
C-2 Default Values of Process Noise Elements ..............................................................................................95
D-1 GPSCard Solution Status ..........................................................................................................................143
D-2 Position Type ............................................................................................................................................143
D-3 RTK Status for Position Type 3 (RT-20) ................................................................................................143
D-4 RTK Status for Position Type 4 (RT-2) ...............................................................................................143
D-5 Receiver Self-Test Status Codes ...............................................................................................................196
D-6 Range Record Format (RGED only) ........................................................................................................199
D-7 Channel Tracking Status ...........................................................................................................................201
D-8 Ambiguity Types ......................................................................................................................................209
D-9 Searcher Status ..........................................................................................................................................209
D-10 RTK Status ................................................................................................................................................209
D-11 GPSCard Range Reject Codes ..................................................................................................................213
D-12 GPSCard Velocity Status ..........................................................................................................................221
D-13 Health and Status Bits ...............................................................................................................................223
D-14 Data ID Type ............................................................................................................................................223
E-1 Comparison of RT-2 and RT-20 ...............................................................................................................225
E-2 RTK Messages Vs. Accuracy ...................................................................................................................225
E-3 RT-2 Performance: Static Mode ...............................................................................................................226
E-4 RT-2 Performance: Kinematic Mode .......................................................................................................226
E-5 RT-2 Degradation With Respect To Data Delay ......................................................................................226
E-6 RT-20 Performance ..................................................................................................................................229
G-1 Reference Ellipsoid Constants ..................................................................................................................234
G-2 Transformation Parameters (Local Geodetic to WGS84) ........................................................................234
I-1
Type 1 !ERRA Types ...............................................................................................................................238
Type 1 !MSGA Types ..............................................................................................................................239
For you convenience these tables, up to and including Appendix E, are also listed in Appendix J, Page 242.
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Software License
SOFTWARE LICENSE
SOFTWARE LICENSE
BY OPENING THE SEALED DISK PACKAGE YOU ARE AGREEING TO BE BOUND BY THE TERMS OF THIS
AGREEMENT. IF YOU DO NOT AGREE TO THE TERMS OF THIS AGREEMENT PROMPTLY RETURN THE
UNOPENED DISK PACKAGE AND THE ACCOMPANYING ITEMS TO NOVATEL INC.
1. License: NovAtel Inc. (“NovAtel”) grants you a non-exclusive license (not a sale) to use one copy of the enclosed NovAtel
software on a single computer, and only with the product whose model number and serial number appear on the envelope.
2. Copyright: NovAtel owns, or has the right to sublicense, all copyright, trade secret, patent and other proprietary rights in the
software and the software is protected by national copyright laws, international treaty provisions and all other applicable
national laws. You must treat the software like any other copyrighted material except that you may either (a) make one copy
of the software solely for backup or archival purposes, or (b) transfer the software to a single hard disk provided you keep the
original solely for backup or archival purposes. You may not copy the product manual or written materials accompanying the
software.
3. Restrictions: You may not: (1) copy (other than as provided for in paragraph 2), distribute, rent, lease or sublicense all or
any portion of the software; (2) modify or prepare derivative works of the software; (3) use the software in connection with
computer-based services business or publicly display visual output of the software; (4) transmit the software over a network, by
telephone or electronically using any means; or (5) reverse engineer, decompile or disassemble the software. You agree to keep
confidential and use your best efforts to prevent and protect the contents of the software from unauthorized disclosure or use.
4. Term and Termination: This Agreement is effective until terminated. You may terminate it at any time by destroying the
software, including all computer programs and documentation, and erasing any copies residing on computer equipment. If you
do so, you should inform NovAtel in writing immediately. This Agreement also will terminate if you do not comply with any
of its terms or conditions. Upon such termination you are obligated to destroy the software and erase all copies residing on
computer equipment. NovAtel reserves the right to terminate this Agreement for reason of misuse or abuse of this software.
5. Warranty: For 90 days from the date of shipment, NovAtel warrants that the media (for example, diskette) on which the
software is contained will be free from defects in materials and workmanship. This warranty does not cover damage caused by
improper use or neglect. NovAtel does not warrant the contents of the software or that it will be error free. The software is
furnished "AS IS" and without warranty as to the performance or results you may obtain by using the software. The entire risk
as to the results and performance of the software is assumed by you.
6. For software UPDATES and UPGRADES, and regular customer support, contact the NovAtel GPS Hotline at
1-800-NOVATEL (Canada and the U.S.A. only), or directly for International Customers 1-403-295-4900, Fax 1-403-295-
4901, e-mail to [email protected], visit out world wide web site at http://www.novatel.ca, or write to:
NovAtel Inc.
Customer Service Dept.
1120 - 68th Avenue NE
Calgary, Alberta,
Canada
T2E 8S5
7. Disclaimer of Warranty and Limitation of Liability:
a.
THE WARRANTIES IN THIS AGREEMENT REPLACE ALL OTHER WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING ANY WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
NOVATEL DISCLAIMS AND EXCLUDES ALL OTHER WARRANTIES. IN NO EVENT WILL NOVATEL'S
LIABILITY OF ANY KIND INCLUDE ANY SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES, INCLUDING
LOST PROFITS, EVEN IF NOVATEL HAS KNOWLEDGE OF THE POTENTIAL LOSS OR DAMAGE.
b.
NovAtel will not be liable for any loss or damage caused by delay in furnishing the software or any other performance
under this Agreement.
c.
NovAtel's entire liability and your exclusive remedies for our liability of any kind (including liability for negligence)
for the software covered by this Agreement and all other performance or nonperformance by NovAtel under or related to this
Agreement are limited to the remedies specified by this Agreement.
This Agreement is governed by the laws of the Province of Alberta, Canada. Each of the parties hereto irrevocably
attorns to the jurisdiction of the courts of the Province of Alberta.
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Software Support
SOFTWARE SUPPORT
SOFTWARE SUPPORT
Software updates are software revisions to an existing model which improves (but does not increase) basic
functionality of the GPS receiver. During the one year warranty coverage following initial purchase, software
updates are supplied free of charge. After the warranty has expired, software updates and updated manuals may be
subject to a nominal charge.
Software upgrades are software releases which increase basic functionality of the receiver from one model to a
higher level model type. When available, upgrades can be purchased at a price which is the difference between the
two model types on the current NovAtel GPS Price List plus a nominal service charge.
Software updates and upgrades are obtained through NovAtel authorized dealers or NovAtel Customer Support.
Contact your local NovAtel dealer for more information.
To locate a dealer in your area, contact NovAtel in any of the following ways:
•
GPS Hotline at 1-800-NOVATEL (1-800-668-2835)
(U.S.A. and Canada only; 8 a.m. - 4:30 p.m. Mountain Standard Time)
•
•
•
•
•
telephone: 1-403-295-4900 (8 a.m. - 4:30 p.m. Mountain Standard Time)
fax: 1-403-295-4901
e-mail: [email protected]
web site: http://www.novatel.ca
postal address:
NovAtel Inc.
Customer Service Dept.
1120 - 68th Avenue NE
Calgary, Alberta
Canada
T2E 8S5
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Foreword
FOREWORD
Congratulations!
Thank you for purchasing a NovAtel GPSCard product.
Whether you have bought a stand alone GPSCard or a packaged receiver you will have also received companion
documents to this manual. They will help you get the hardware operational. Afterwards, this text will be your
primary MiLLennium GPSCard command and logging reference source.
Scope
The MiLLennium Command Descriptions Manual describes each command and log that the MiLLennium
GPSCard is capable of accepting or outputting. Sufficient detail is provided so that you can understand the
purpose, syntax, and structure of each command or log and be able to effectively communicate with the GPSCard,
thus enabling the developer to effectively use and write custom interfacing software for specific needs and
applications. The manual is organized into chapters which allow easy access to appropriate information about the
GPSCard.
This manual does not address in detail any of the GPSCard hardware attributes or installation information. Please
consult the appropriate companion manual for hardware or system technical specifications information.
Furthermore, should you encounter any functional, operational, or interfacing difficulties with the GPSCard,
consult the appropriate hardware manual for NovAtel warranty and customer support information.
Prerequisites
As this reference manual is focused on the GPSCard commands and logging protocol, it is necessary to ensure that
the GPSCard has been properly installed and powered up according to the instructions outlined in the companion
hardware manual before proceeding.
To use your NovAtel GPS receiver effectively, you should be familiar with the Global Positioning System (GPS)
as it applies to positioning, navigation, and surveying applications. For your reference Appendix A of this manual
provides an overview of the Global Positioning System.
This manual covers the full performance capabilities of all MiLLennium GPSCards. Every MiLLennium can be
upgraded through a family of firmware models, each having unique features. Therefore, depending on the software
configuration of your MiLLennium, certain commands and logs may not be accessible. Feature-tagging symbols
have been created to help clarify which commands and logs are only available with a certain option:
RTK
Features available only with MiLLennium GPSCards equipped with the RT-20 or RT-2 option
Features available only on MiLLennium GPSCards equipped with the WAAS option
WAAS
What’s New In Version 4.50?
1.
2.
3.
RTCM Types 18 & 19, or RTCM Type 22, are now supported with Type 3 for reference position.
It is also possible to send and receive CMR messages.
Two new Wide Area Augmentation System (WAAS) commands, WAASCORRECTION and
IONOMODEL, enable the use of the WAAS corrections in the position filter. By default these features
are disabled.
4.
A new WAAS log, WALA/B, provides WAAS satellite-specific data.
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1
Quick Start
1 QUICK START
1
QUICK START
This chapter will help you get started quickly regardless of whether you wish to carry out real-time kinematic
(RTK) positioning, operate in differential modes or simply log data. Each section references additional sources of
information.
1.1 INSTALLATION
For more detailed instructions on the installation and set up of your GPSCard please refer to the accompanying
MiLLennium GPSCard Guide to Installation and Operation.
The MiLLennium receiver is designed for flexibility of integration and configuration. You are free to select an
appropriate data and signal interface, power supply system and mounting structure. This concept allows OEM
purchasers to custom-design their own GPS-based positioning system around the MiLLennium GPSCard.
Installing the MiLLennium GPSCard typically consists of the following:
•
Mount the GPSCard in a secure enclosure to reduce environmental exposure, RF
interference and vibration effects
•
Pre-wire the I/O harness and the 64-pin DIN female connector for power and
communications, then connecting them to the OEM series GPSCard
•
Install the GPSAntenna, then connect to the GPSCard
•
(Optional) Install an external oscillator if additional precision and stability is required
OPERATION
Once the hardware and software installations have been completed, you are now ready to begin initial operation of
the GPSCard receiver.
Communication with the MiLLennium GPSCard consists of issuing commands through the COM1 or COM2 port
from an external serial communications device. This could be either a terminal or an IBM-compatible PC that is
directly connected to a MiLLennium GPSCard COM port using a null modem cable.
TURNING ON
The initial operating software and firmware of the MiLLennium GPSCard resides in its read-only memory. As
such, the unit “self-boots” upon power-up. The green LED indicator should blink about once per second if the unit
is operating normally. The red one lights up if an error is detected during a self-test. The self-test status word can
be viewed in the RGEA/B/D and RVSA/B data output logs.
If a persistent error develops please contact the NovAtel GPS Customer Service Department for further assistance
COMMUNICATION DEFAULT SETTINGS
COM1 and COM2 for the MiLLennium GPSCards are defaulted to the following RS232 protocol:
•
9600 bps, no parity, 8 data bits, 1stop bit, no handshake, echo off
Graphical Interface
Your GPSCard comes with a disk containing NovAtel’s graphical interface software GPSolution, a Microsoft
Windows-based program, enabling you to use your GPSCard without struggling with communications protocol or
writing make-do software.
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Quick Start
The View menu options allow you to select or de-select various visual aids and display screens. Take a look at all
of the options and keep open those you wish to display. To send commands and log data the Command Console
screen should be visible. ASCII format logs can be monitored on the ASCII Record screen.
e.g. On the command line of the Command Console screen type:log com1 posa once
After you hit the <Enter> key the ASCII Record screen will display the output for your current position. The POSA/
1.2 DATA LOGGING
The GPSCard has four major logging formats:
•
•
•
•
NovAtel Format Data Logs (ASCII/Binary)
NMEA Standard Format Data Logs (ASCII)
RTCM Standard Format Data Logs (Binary)
RTCA Standard Format Data Logs (Binary)
All data types can be logged using several methods of triggering each log event. Each log is initiated using theLOG
command. The LOG command and syntax are listed following.
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Quick Start
Syntax: log [port],datatype,[trigger],[period],[offset],{hold}
Syntax
LOG
Description
Example
LOG
port
COM1 or COM2
Defaults to the port that the command was entered on.
COM1
datatype Enter one of the valid ASCII or Binary Data Logs (see Chapter 4, Page 34 and Appendix D, Page 136)
trigger Enter one of the following triggers.
POSA
ONTIME
ONCE
Immediately logs the selected data to the selected port once. Default if trigger field is left
blank.
ONMARK
Logstheselecteddatawhena MARKIN electrical event isdetected. Outputsinternal buffers
at time of mark - does not extrapolate to mark time. Use MKPA/B for extrapolated position
Range Value
Default
at time of mark.
ONNEW
Logs the selected data each time the data is new even if the data is unchanged.
Logs the selected data only when the data has changed.
ONCHANGED
ONTIME
[period], [offset]
Immediately logs the selected data and then periodically logs the selected data at a
frequency determined by the period and offset parameters. The logging will continue until
an UNLOG command pertaining to the selected data item is received (see UNLOG
CONTINUOUSLY Will log the data all the time. The GPSCard will generate a new log when the output buffer
associated with the chosen port becomes empty. The continuously option was designed for
use with differential corrections over low bit rate data links. This will provide optimal record
generation rates. The next record will not be generated until the last byte of the previous
record is loaded into the output buffer of the UART.
period
Use only with the ONTIME trigger. Units for this parameter are seconds. The selected period may be any of the 60
following values: 0.05, 0.10, 0.20, 0.25, 0.50, 1, 2, 3, ... , 3600 seconds but may be limited by the GPSCard model
and previously requested logs. Selected data is logged immediately and then periodic logging of the data will start
at the next even multiple of the period. If a period of 0.20 sec is chosen, then data will be logged when the receiver
time is at the 0.20, 0.40, 0.60 and the next (0.80) second marks. If the period is 15 seconds, then the logger will
log the data when the receiver time is at even 1/4 minute marks. The same rule applies even if the chosen period
is not divisible into its next second or minute marks. If a period of 7 seconds is chosen, then the logger will log at
the multiples of 7 seconds less than 60, that is, 7, 14, 21, 28, 35, 42, 49, 56 and every 7 seconds thereafter.
offset
hold
Use only with the ONTIME trigger. Units for this parameter are seconds. It provides the ability to offset the
logging events from the above startup rule. If you wished to log data at 1 second after every minute you would set
the period to 60 seconds and the offset to 1 second (Default is 0).
1
Will prevent a log from being removed when the UNLOGALL command is issued
HOLD
The syntax for a command can contain optional parameters (OPT1, OPT2, ...). OPT2 may only be used if it
is preceded by OPT1. OPT3 may only be used if it is preceded by OPT2 and so on. Parameters after and
including OPT1 will be surrounded by square brackets.
An optional parameter such as {hold} surrounded by braces may be used with the log command without any
preceding optional parameters. Example:log com1 posa 60 1 hold
log com1 posa hold
Example:
log com1,posa,ontime,60,1
If the LOG syntax does not include a trigger type, it will be output only once following execution of the LOG
command. If trigger type is specified in the LOG syntax, the log will continue to be output based on the trigger
specification. Specific logs can be disabled using the UNLOG command, whereas all enabled logs will be disabled
by using the UNLOGALL command (see Chapter 2, Page 23 and Appendix C, Page 79). All activated logs will be
The [port] parameter is optional. If [port] is not specified, [port] is defaulted to the port that the command was
received on.
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1
Quick Start
COMMONLY USED LOGS
Type
Positioning
Logs
PRTKA/B
POSA/B
Trigger
ontime or onmark
Post Processing
NMEA Position
RGEA/B/D
REPA/B, ALMA/B
ontime
onchanged
GPGLL
GPGGA
ontime or onmark
Other useful logs are
•
•
•
•
•
RCCA to list the default command settings
ETSA to monitor the channel tracking status
SATA to observe the satellite specific data
DOPA to monitor the dilution of precision of the current satellite constellation
RVSA to monitor the receiver status
For further information on output logging see Chapter 4, Page 34 and the individual logs listed alphabetically in
Use the HELP command to list all available commands. For more information on sending commands see Chapter
1.3 DIFFERENTIAL OPERATION
The MiLLennium GPSCard is ideal for design into DGPS systems because it is capable of operating as either a
reference station or a rover station. .
The GPSCard is capable of utilizing various formats of differential corrections. These formats are divided into two
primary groups RTCM and RTCA.
For detailed data structure concerning these logs, please see:
Chapter 3, Page 34
Chapter 4, Page 45
Appendix D, Page 136
Establish a Data Link
Operating the GPSCard with a DGPS system requires that the reference station broadcast differential correction
data messages to one or more rover receivers. As there are many methods by which this can be achieved, it is up
to you to establish an appropriate data link that best suits your user requirements.
Whatever data link is chosen, the operator of the reference station will want to ensure that the bit rate of data
transmission is suitable for the anticipated data link and remote users. Use the GPSCard COMn command to the
COM port default bit rate (default is 9600 bps, no parity, 8 data bits, 1 stop bit, no handshake, echo off).
Note that the GPSCard COMn_DTR and COMn_RTS commands are available for remote device keying (such as
a radio transmitter). These commands allow for flexible control of the DTR and RTS lines to be precisely timed
with log transmissions.
Further information may be found in Appendix A.
Table 1-1, following, is a GPSCard pseudorange differential initialization summary.
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Quick Start
Table 1-1 GPSCard Pseudorange Differential Initialization Summary
Reference Station
Remote Station
Required:
Required:
FIX POSITION lat lon hgt id (health)
ACCEPT port DATATYPE
LOG port DATATYPE ontime 5
Recommended Options:
Recommended Options:
LOG DATATYPES (binary):
ACCEPT DATATYPES (binary):
RTCMB
RTCAB
RTCM
RTCA
RTCM
RTCA
LOG DATATYPES (acii):
ACCEPT COMMANDS (ascii):
RTCMA
RTCAA
RTCMA
RTCAA
Related Commands/Logs:
Related Commands/Logs:
RTCMRULE
RTCMRULE
DATUM
POSA/B
VLHA/B
CDSA/B
GPGGA
DATUM
Example 1:
Example 1:
fix position 51.3455323 -114.2895345 1201.123 555 0
log com 1 RTCM ontime 2
accept com2 rtcm
log com1 posa ontime 1
Example 2:
Example 2:
fix position 51.3455323 -114.2895345 1201.123 555 0
log com2 rtcaa ontime 2
accept com2 commands
log com1 posa ontime 0.2
log com1 vlha ontime 0.2
Note: Italicized entries indicate user definable.
Initialization - Reference Station
Differential mode of operation is established at the reference station through a two step process: fix position and
logging observation and correction data.
FIX POSITION
The reference station must initialize the precise position of its reference antenna phase centre (lat/lon/hgt). This is
accomplished by utilizing the GPSCard FIX POSITION command. The syntax is as follows:
Syntax:
FIX POSITION
lat lon height station id
health
Example:
fix position 51.3455323,-114.2895345,1201.123,555,0
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NOTE 1: Entry of the station ID and health are optional. For a CMR correction type the station ID must be < 31.
NOTE 2: The accuracy of the reference station’s FIX POSITION setting will directly affect the accuracy of its
computed differential corrections. Good results at the rover station are dependent on the reference
station’s combined position errors being kept to a minimum (e.g., fix position error + multipath errors).
NOTE 3: The GPSCard performs all computations based on WGS84 and is defaulted as such, regardless of
DATUM command setting. The datum in which you choose to operate is converted from WGS84;
therefore, all differential corrections are based on WGS84. Ensure that any change in your operating
datum is set prior to FIX POSITION.
NOTE 4: When transmitting RTCM type data, the GPSCard has various options for assigning the number of data
concerning RTCM data bit rule settings.
NOTE 5: The FIX POSITION “health” field entered will be reported in word 2 of the RTCM message frame header.
Once the GPSCard has its position data fixed and is tracking three or more satellites, it is now ready to transmit
differential correction and observation data to the rover stations.
LOG BROADCAST DATA
Assuming that a data link has been established, use the GPSCard log command to send observation and differential
corrections data for broadcast to the rover stations.
Syntax:
LOG port
data ontime seconds
Example:
log com1 rtcm ontime 5
REMINDER: Ensure that the bit rate of the data link is suitable for the differential type, logging rate and
maximum message length of the data type being logged.
1.4 RTK MODE
NovAtel’s RTK system utilizes proprietary messaging as well as RTCM Types 18 and 19, and can also receive
CMR messages from a non-NovAtel base station. For more information on specific message formats please see
NOTE: No guarantee is made that the MiLLennium will meet its performance specifications if non-NovAtel
accessories (e.g. antenns, RF cable) are used.
Data Communications Link
It is the user’s responsibility to provide a data communications link between the reference station and remote
station. The data transfer rate must be high enough to ensure that sufficient reference station messages reach the
remote station to keep extrapolation errors from growing too large; see Table 1-2.
Table 1-2 Latency-Induced Extrapolation Error
Time since last reference station observation
Typical extrapolation error (CEP)
0-2 seconds
2-7 seconds
7-30 seconds
1 cm/sec
2 cm/sec
5 cm/sec
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Generally, a communications link capable of data throughput at a rate of 4800 bits per second or higher is
sufficient. However, it is possible to satisfactorily use a lower rate (e.g. 2400 bps) with the RTCA, RTCM59 and
CMR formats. RTCM Types 18 and 19 may require a higher rate; see Chapter 4, Message Formats, Page 45 for
additional information. The minimum data transfer rate is based on the following:
1. RT-2 requires that the reference station periodically transmit two RTCA Standard Type 7 messages:
•
An RTCAOBS message contains reference station satellite observation information, and
should be sent once every 1 or 2 seconds.
•
An RTCAREF message contains reference station position information, and should be
sent once every 10 seconds.
OR periodically transmit an RTCM Type 18 and RTCM Type 19 (RTCM1819) message together with an
RTCM Type 3 message:
•
A Type 3 message contains reference station position information, and should be sent
once every 10 seconds (although it is possible to send it as infrequently as once every 30
seconds).
•
RTCM1819 gives raw measurement information (Type 18 provides carrier phase
measurements, while Type 19 provides pseudorange measurements) and should be sent
once every 1 or 2 seconds.
Note: This message can be sent in RTCM Version 2.1 or Version 2.2 format, controlled with the RTKMODE
command.
and, optionally, also periodically transmit an RTCM Type 22 message together with an RTCM Type 3
message:
•
A Type 3 message contains reference station position information, and should be sent
once every 10 seconds (although it is possible to send it as infrequently as once every 30
seconds).
•
A Type 22 message gives extended reference station parameters and should be sent once
every 10 seconds.
transmitting CMR corrections:
•
•
A CMROBS message contains reference station satellite observation information, and
should be sent once every 1 or 2 seconds.
A CMRREF message contains reference station position information, and should be sent
once every 10 seconds.
2. RT-20 requires that the reference station periodically transmit either the RTCA messages listed above (the
recommended option), or RTCM 1819 or CMR messages or the RTCM SC-104 Type 3 & 59N messages:
•
A Type 3 message contains reference station position information, and should be sent
once every 10 seconds (although it is possible to send it as infrequently as once every 30
seconds).
•
A Type 59N message contains reference station satellite observation information, and
should be sent once every 2 seconds.
Further information on RTCA, RTCM and CMR message formats is contained in Chapter 6.
System Initialization
The RTK system is designed for ease of use: you set up the remote station, enter a command so that it accepts RT-
2 or RT-20 messages from the reference station, and are ready to go. There are options, however, which can be
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used to adapt the system to a specific application. Some options apply only to the reference station, while others
apply only to the remote station. Detailed descriptions can be found in Appendix C, Commands Summary.
In the following sections, keep the following in mind:
•
•
Dynamics modes. For reliable performance the antenna should not move more than 1-2
When using the FIX POSITION command, the height entered must be in metres above mean
sea level; it will be converted to ellipsoidal height inside the receiver. You can enter an
undulation value, if desired, using the UNDULATION command; if none is entered, the
receiver estimates an undulation with its internal table. The format of the optional station
ID field depends on whether RTCM or RTCA messages are being used: if RTCM, any
number from 0 - 1023 is valid, while if RTCA, any 4-character string of numbers and
additional information on the station id field.
•
The COMn field refers to the serial port (either COM1 or COM2) to which data
communications equipment is connected. The serial port assignment at the reference and
remote stations need not be the same; e.g. a radio transmitter might be connected to
COM1 at the reference station, and a radio receiver to COM2 at the remote station.
INITIALIZATION FOR RTCA-FORMAT MESSAGING (RT-2 OR RT-20)
The following commands will enable RTCA-format messaging and allow RT-2 or RT-20 to operate with the
remote station either at rest or in motion. Note that the optional station health field in the existing FIX POSITION
command is not currently implemented in NovAtel’s RTCA messages, though it will be in the future.
1. At the reference station:
fix position lat,lon,height,station id
log comn,rtcaref,ontime,interval
log comn,rtcaobs,ontime,interval
Example:
fix position 51.11358042,-114.04358013,1059.4105,”RW34”
log com1,rtcaref,ontime,10
log com1,rtcaobs,ontime,2
2. At the remote station:
accept comn,rtca
Example:
accept com2,rtca
Congratulations! Your RTK system is now in operation!
INITIALIZATION FOR RTCM59-FORMAT MESSAGING (RT-20 ONLY)
Although RT-20 can operate with either RTCA or RTCM-format messaging, the use of RTCA-format messages is
recommended (see Chapter 4, Page 45 for further information on this topic). Nevertheless, the following
commands will enable RTCM59-format messaging and allow RT-20 to operate with the remote station either at
rest or in motion:
1. At the reference station:
fix position lat,lon,height,station id,station health
log comn,rtcm3,ontime,interval
log comn,rtcm59,ontime,interval
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Example:
fix position 51.11358042,-114.04358013,1059.4105,119,0
log com1,rtcm3,ontime,10
log com1,rtcm59,ontime,2
2. At the remote station:
accept comn,rtcm
Example:
accept com2,rtcm
Congratulations! Your RT-20 system is now in operation!
Monitoring Your RTK Output Data
At the remote station, you could now select any or all of these output logs for positioning information:
•
•
•
•
•
•
BSLA/B Baseline Measurement
NMEA-format logs
POSA/B Computed Position
PRTKA/B Best Position
RPSA/B Reference Station Position & Health
RTKA/B RTK Output - Time Matched Positions
The POSA/B, PRTKA/B and NMEA-format logs contain the low-latency position; the RTKA/B logs contain the
matched position. The low-latency solution is the recommended one for kinematic users, while the matched
solution is the one recommended for stationary users. For a discussion on low-latency and matched positions, see
Options for Logging Differential Corrections
SET DGPSTIMEOUT
The DGPSTIMEOUT command allows the reference station to set the delay by which it will inhibit utilization of new
ephemeris data in its differential corrections. This delay ensures that the remote receivers have had sufficient time
to collect updated ephemeris data as well.
A delay of 120 to 130 seconds will typically ensure that the rover stations have collected updated ephemeris. After
the delay period is passed, the reference station will begin using new ephemeris data. To enter an ephemeris delay
value, you must first enter a numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference
station, DGPS delay will be ignored (see the DGPSTIMEOUT command found in Chapter 2, Page 23 and Appendix
C, Page 90 for further information on using this command at rover stations.)
Syntax:
DGPSTIMEOUT dgps delay
ephem delay
Description
Command
DGPSTIMEOUT
dgps delay
Option
Default
Command
min.
2
Maximum age in seconds
60
max.
1000
ephem delay
min.
0
Minimum time delay in seconds
120
max.
600
Example:
dgpstimeout 2,300
USING RTCM SC-104 LOG TYPES
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RTCM SC-104 is a standard for transmitting differential corrections between equipment from different
manufacturers. The NovAtel GPSCard is capable of transmitting or receiving RTCM data.
To facilitate transmitting the RTCM data over shared data links, the GPSCard is also capable of sending the RTCM
log in NovAtel ASCII format (RTCMA) or with the NovAtel binary header (RTCMB) added to allow synchronous
transmission and reception along with other data types.
REMEMBER: When sending or receiving RTCM log types, it is important to ensure that all connected
equipment are using the same RTCMRULE for compatibility.
The easiest method to send RTCM standard logs is from the COM1 or COM2 ports of the reference GPSCard. The
easiest method to receive the RTCM data is through the COM1 or COM2 port of the rover GPSCard. The rover
GPSCard must issue the “ACCEPT port RTCM” command to dedicate a port before it will accept the RTCM data
into that port.
The RTCMA log can be intermixed with other NovAtel ASCII data over a common communication port. It will be
directly interpreted by a rover GPSCard as a special data input command ($RTCM). “ACCEPT port
COMMANDS” must be used with this input command. A non-NovAtel rover station will need to strip off the
header ($RTCM) and terminator (*xx), then convert the hexadecimal data to binary before the RTCM standard data
can be retrieved.
The RTCMB log can be intermixed with other NovAtel binary data over a common communication port.
REMEMBER: Use the CDSA/B logs to monitor the COM port activity, success, and decoding errors.
USING RTCA LOG TYPES
The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support
Differential Global Navigation Satellite System (DGNSS) aviation applications. The perceived advantage to using
RTCA type messages for transmitting and receiving differential corrections versus using RTCM type messages is that
RTCM transmits 30-bit words, and the data is difficult to decode and process because of the parity algorithm and
irregular word sizes used. RTCA is transmitted in 8-bit words, which are easier to generate, process and decode. The
RTCA messages are therefore smaller, they have a 24 bit CRC that is much more robust than RTCM messages, and
they permit the use of a four-alpha-character station ID.
RTCA standard logs can be received through the COM1 or COM2 port of the rover GPSCard. The remote
GPSCard must issue the “ACCEPT port RTCA” command to dedicate a port before it will accept the RTCA data
input to that port. The RTCA logs cannot be intermixed with other logs.
The RTCAA log can be intermixed with other NovAtel ASCII data over a common communications port. It will
be directly interpreted by a rover GPSCard as a special data input command ($RTCA). “ACCEPT port commands”
must be used with this input command. A non-NovAtel rover station will need to strip off the header ($RTCA) and
terminator (*xx), then convert the hexadecimal data to binary before the RTCA standard can be retrieved.
The RTCAB log can be intermixed with other NovAtel binary data. The remote GPSCard identifies the RTCAB log
by the message block identifier contained in the message, and will interpret only the RTCA data portion of the log.
NOTE: The CDSA/B logs may be used to monitor the COM port activity and differential data decode success.
Initialization - Rover Station
It is necessary to initialize the rover receiver to accept observation data from the reference station. If the receiver
is not correctly initialized, it will proceed to compute solutions in single point positioning mode.
Before initializing, ensure that the data link with the reference station has been properly set up. As well, ensure that
the COM port which is to receive the differential data is set up to match the bit rate and protocol settings of the
reference station broadcast data.
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Establishing differential mode of operation at the rover receiver is primarily a one-step process whereby the accept
command is used to enable reception of observation data from the reference station.
ACCEPT COMMAND
The accept command is primarily used to set the GPSCard’s COM port command interpreter for acceptance of
Syntax
ACCEPT port
mode
Example:
accept com2 rtcm
Once intitialized, the rover GPSCard receiver will operate in single point mode until the differential messages are
received. If the data messages are lost, the GPSCard will revert to single point positioning until the pseudorange
correction messages are restored.
NOTE: Ensure that the GPSCard RTCMRULE settings agree with the bit rule being transmitted by the RTCM
reference station. Unless otherwise set, all GPSCards default to 6CR.
LOG POSITION DATA AND OTHER USEFUL DATA
The GPSCard remote receiver has many options for information data logging. To monitor position status, the user
may find the PRTKA/B logs to be the most informative. Other options exist, such as POSA/B and GPGGA. As well,
velocity data can be found in the VLHA/B, SPHA/B and GPVTG logs. It is really up to your specific applications as to
the full range of logs you require.
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Command Descriptions
2 COMMAND DESCRIPTIONS
2
COMMAND DESCRIPTIONS
2.1 GENERAL
This section describes all commands accepted by the GPSCard with the exception of the "Special Data Input
Commands". They are listed in alphabetical order. For descriptions of output logs using the LOG command, see
Chapter 3.
The GPSCard is capable of responding to over 50 different input commands. You will find that once you become
familiar with these commands, the GPSCard offers a wide range in operational flexibility. All commands are
accepted through the COM1 and COM2 serial ports. See Table 2-1, Page 25 for a complete command listing.
NOTE: You will find the HELP command a useful tool for inquiring about the various commands available.
The following rules apply when entering commands from a terminal keyboard:
•
The commands are not case sensitive (COMMAND or command).
e.g.
e.g.
HELP or help
FIX POSITION or fix position
•
All commands and required entries can be separated by a space or a comma
(command,variable OR command variable).
e.g.
e.g.
e.g.
e.g.
e.g.
e.g.
e.g.
e.g.
datum,tokyo
datum tokyo
fix,position,51.3455323,-117.289534,1002
fix position 51.3455323 -117.289534 1002
com1,9600,n,8,1,n,off
com1 9600 n 8 1 n off
log,com1,posa,onchanged
log com1 posa unchanged
•
At the end of a command or command string, press the <CR> key. A carriage return is what
the card is looking for and is usually the same as pressing the <Enter> key.
•
Most command entries do not provide a response to the entered command. Exceptions to
this statement are the VERSION and HELP commands. Otherwise, successful entry of a
command is verified by receipt of the COM port prompt (i.e. COM1> or COM2>).
The syntax for a command can contain optional parameters (OPT1, OPT2, ...). OPT2 may only be used if it
is preceded by OPT1. OPT3 may only be used if it is preceded by OPT2 and so on. Parameters after and
including OPT1 will be surrounded by square brackets.
An optional parameter such as {hold} surrounded by braces may be used with the log without any preceding
optional parameters
Example:
log com1 posa 60 1 hold
log com1 posa hold
When the GPSCard is first powered up, or after a FRESET command, all commands will revert to the factory default
settings. An example is shown below. The SAVECONFIG command can be used to modify the power-on defaults.
Use the RCCA log to reference station command and log settings.
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Command Descriptions
NOTE: All previously stored configurations that were saved to non-volatile memory are erased (including
Saved Config, Saved Almanac, and Channel Config).
Example:
Optional calculation of the checksum
When an input command is followed by an optional checksum, the checksum will be verified before the command
is executed. The checksum is the result of the logical exclusive-OR operation on all the bits in the message. So,
the checksum of a command with parameters will change if the parameters are modified.
NOTE: The command must be typed in uppercase for the proper checksum to be calculated.
As an example, it may be essential to ensure that a receiver has received and executed the correct command from
a host computer. If the checksum were calculated by the sender and attached to the command, the receiver would
be able to recognize if errors had been introduced and if so, alert the sender to this with an “Invalid Command
CRC” message.
Example:
FIX HEIGHT 4.567[CR][LF]
FIX HEIGHT 4.567*66[CR][LF]
Both are acceptable, but only the second one would trigger the verification function.
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Command Descriptions
2.2 STANDARD COMMAND TABLES
Table 2-1 lists the commands by function while Table 2-2 is an alphabetical listing of commands. Please see
Appendix C, Page 79 for a more detailed description of individual commands which are listed alphabetically.
Table 2-1 Commands By Function Table
COMMUNICATIONS, CONTROL AND STATUS
Commands
Descriptions
Power to the low-noise amplifier of an active antenna
COMn port configuration control
DTR handshaking control
ANTENNAPOWER
COMn
COMn_DTR
COMn_RTS
RTS handshaking control
1
Differential Protocol Control
DIFF_PROTOCOL
FREQUENCY_OUT
LOG
Variable frequency output (programmable)
Logging control
MESSAGES
RINEX
Disable error reporting from command interpreter
Configure the user defined fields in the file header
Sets up RTCM bit rule
RTCMRULE
RTCM16T
SEND
Enters an ASCII message
Sends ASCII message to COM port
Sends non-printable characters
SENDHEX
Add an offset to the L1 pseudorange to compensate for
signal delays
1
SETL1OFFSET
1
Intended for advanced users of GPS only
GENERAL RECEIVER CONTROL AND STATUS
Commands Descriptions
$ALMA
Download almanac data file
CRESET
Reset receiver to factory default
Set correlator tracking bandwidth
On-line command help
DYNAMICS
HELP
RESET
Performs a hardware reset (OEM only)
Saves the latest almanac in NVM
Saves current configuration (OEM only)
Injects receiver time of 1PPS
SAVEALMA
SAVECONFIG
$TM1A
VERSION
Software/hardware information
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Command Descriptions
Table 2-1 Commands By Function Table (continued)
POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL
Commands Descriptions
1
Sets amount of carrier smoothing
CSMOOTH
DATUM
Choose a DATUM name type
ECUTOFF
FIX HEIGHT
FIX POSITION
FRESET
Satellite elevation cut-off for solutions
Constrains to fixed height (2D mode)
Constrains to fixed lat, lon, height
Clears all data which is stored in NVM
Download ionospheric correction data
$IONA
What ionospheric correction to use (MiLLennium with the
WAAS option)
IONOMODEL
LOCKOUT
Deweights a satellite in solutions
1
Position, velocity and acceleration in ECEF coordinates
Setup the RTK mode
$PVAA
RTKMODE
UNDULATION
USERDATUM
WAASCORRECTION
Ellipsoid-geoid separation
User-customized datum
Controls handling of WAAS corrections.
1
Intended for advanced users of GPS only.
SATELLITE TRACKING AND CHANNEL CONTROL
Commands
Descriptions
$ALMA
ASSIGN
CONFIG
Download almanac data file
Satellite channel assignment
Switches the channel configuration of the GPSCard
Sets correlator tracking bandwidth
Aids high velocity reacquisition
Reset PRN health
DYNAMICS
FIX VELOCITY
RESETHEALTH
SETHEALTH
Overrides broadcast satellite health
WAYPOINT NAVIGATION
Commands
Descriptions
Magnetic variation correction
Waypoint input
MAGVAR
SETNAV
DIFFERENTIAL REFERENCE STATION
Commands
Descriptions
DGPSTIMEOUT
FIX POSITION
LOG
Sets ephemeris delay
Constrain to fixed (reference)
Selects required differential-output log
Implements position averaging for reference station
Selects RTCM bit rule
POSAVE
RTCMRULE
SETDGPSID
Set reference station ID
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Command Descriptions
Table 2-1 Commands By Function Table (continued)
DIFFERENTIAL REMOTE STATION
Commands
Descriptions
Accepts RTCM1, RTCA or RTCAB differential inputs
Input almanac data
ACCEPT
$ALMA
DGPSTIMEOUT
RESET
Set maximum age of differential data accepted
Performs a hardware reset
$RTCA
RTCA differential correction input (ASCII)
RTCM differential correction input (ASCII)
Selects RTCM bit rule
$RTCM
RTCMRULE
SETDGPSID
Select differential reference station ID to receive
CLOCK INFORMATION, STATUS, AND TIME
Commands
Descriptions
Enable clock modelling & 1PPS adjust
Differential protocol control
CLOCKADJUST
1
DIFF_PROTOCOL
EXTERNALCLOCK
Sets default parameters of an optional external oscillator
EXTERNALCLOCK FREQUENCY Sets clock rate
1
Enable or disable time synchronization
Download UTC data
SETTIMESYNC
$UTCA
1
Intended for advanced users of GPS only
Table 2-2 GPSCard Command Summary
Description
Command
Syntax
$ALMA
Injects almanac
(follows NovAtel ASCII log format)
$IONA
Injects ionospheric refraction corrections
Injects latest computed position, velocity and acceleration
Injects raw GPS ephemeris data
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
accept port,option
$PVAA
$REPA
$RTCA
Injects RTCA format DGPS corrections in ASCII (Type 1)
Injects RTCM format differential corrections in ASCII (Type 1)
Injects receiver time of 1 PPS
$RTCM
$TM1A
$UTCA
Injects UTC information
ACCEPT
Port input control (set command interpreter)
Power to the low-noise amplifier of an active antenna
Assign a prn to a channel #
ANTENNAPOWER
ASSIGN
antennapower flag
assign channel,prn,doppler, search window
unassign channel
UNASSIGN
UNASSIGNALL
CLOCKADJUST
COMn
Un-assign a channel
Un-assign all channels
unassignall
Disable clock steering mechanism
Initialize Serial Port (1 or 2)
clockadjust switch
comn bps,parity,databits,stopbits, handshake,echo
comn_dtr control,active,lead,tail
comn_rts control,active,lead,tail
config cfgtype
COMn_DTR
COMn_RTS
CONFIG
Programmable DTR lead/tail time
Programmable RTS lead/tail time
Switches the channel configuration of the GPSCard
Configuration reset to factory default
Sets carrier smoothing
CRESET
creset
CSMOOTH
DATUM
csmooth value
Choose a DATUM name type
datum option
USERDATUM
User defined DATUM
userdatum semi-major,flattening,dx,dy,dz, rx,ry,rz,
scale
DGPSTIMEOUT
Sets maximum age of differential data to be accepted and ephemeris dgpstimeout value value
delay
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Command Descriptions
DIFF_PROTOCOL
Differential correction message encoding and decoding for
implementation in the GPS card firmware
diff_protocol type key
or diff_protocol disable
or diff_protocol
DYNAMICS
Set receiver dynamics
dynamics option [user_dynamics]
ecutoff angle
ECUTOFF
Set elevation cutoff angle
EXTERNALCLOCK
Sets default parameters of an optional external oscillator
Sets clock rate
externalclock option
EXTERNALCLOCK
FREQUENCY
external frequency clock rate
FIX HEIGHT
Sets height for 2D navigation
fix height height [auto]
FIX POSITION
FIX VELOCITY
Set antenna coordinates for reference station
fix position lat,lon,height [station id] [health]
Accepts INS xyz (ECEF) input to aid in high velocity reacquisition of fix velocity vx,vy,vz
SVs
UNFIX
Remove all receiver FIX constraints
Variable frequency output (programmable)
Clears all data which is stored in non-volatile memory
On-line command help
unfix
FREQUENCY_OUT
FRESET
frequency_out n,k
freset
HELP or ?
help option or
lockout prn
unlockout prn
unlockoutall
? option
LOCKOUT
UNLOCKOUT
UNLOCKOUTALL
LOG
Lock out satellite
Restore satellite
Restore all satellites
Choose data logging type
log [port],datatype,[trigger],[period],[offset],{hold}
unlog [port],data type
unlogall [port]
UNLOG
Disable a data log
UNLOGALL
MAGVAR
Disable all data logs
Set magnetic variation correction
Disable error reporting from command interpreter
Implements position averaging for reference station
Performs a hardware reset (OEM only)
Configure the user defined fields in the file headers
magvar value
MESSAGES
POSAVE
messages port,option
posave maxtime, maxhorstd, maxverstd
reset
RESET
RINEX
rinex cfgtype
RTCM16T
Enter an ASCII text message to be sent out in the RTCM data stream rtcm16t ascii message
RTCMRULE
RTKMODE
SAVEALMA
SAVECONFIG
SEND
Set variations of the RTCM bit rule
Set up the RTK mode
rtcmrule rule
rrtkmode argument, data range
savealma option
saveconfig
Save the latest almanac in non-volatile memory
Save current configuration in non-volatile memory (OEM only)
Send an ASCII message to any of the communications ports
Sends non-printable characters in hexadecimal pairs
Enter in a reference station ID
send port ascii-message
sendhex port data
setdgpsid option
sethealth prn,health
resethealth prn
SENDHEX
SETDGPSID
SETHEALTH
RESETHEALTH
RESETHEALTHALL
SETL1OFFSET
SETNAV
Override PRN health
Reset PRN health
Reset all PRN health
resethealthall
Add an offset to the L1 pseudorange to compensate for signal delays setL1offset distance
Set a destination waypoint
setnav from lat,from lon,to lat, to lon,track offset, from
port,to port
SETTIMESYNC
UNDULATION
VERSION
Enable or disable time synchronization
Choose undulation
settimesync flag
undulation separation
version
Current software and hardware information
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Command Descriptions
2.3 WAAS
The Wide Area Augmentation System (WAAS) is a safety-critical system that provides a quality of positioning
information previously unavailable. The WAAS improves the accuracy, integrity, and availability of the basic GPS
signals. In the future, the wide area of coverage for this system will include the entire United States and some
outlying areas. At the time of publication, there is one test satellite over the Pacific Ocean and therefore there is
only coverage for the western half of the United States.
The primary functions of WAAS include:
•
•
•
•
•
•
•
•
data collection
determining ionospheric corrections
determining satellite orbits
determining satellite clock corrections
determining satellite integrity
independent data verification
WAAS message broadcast and ranging
system operations & maintenance
As shown in Figure 2-2, the WAAS is made up of a series of Wide Area Reference Stations, Wide Area Master
Stations, Ground Uplink Stations and Geostationary Satellites (GEOs). The Wide Area Reference Stations, which
are geographically distributed, pick up GPS satellite data and route it to the Wide Area Master Stations where wide
area corrections are generated. These corrections are sent to the Ground Uplink Stations which up-link them to the
GEOs for re-transmission on the GPS L1 frequency. These GEOs transmit signals which carry accuracy and
integrity messages, and which also provide additional ranging signals for added availability, continuity and
accuracy. These GEO signals are available over a wide area and can be received and processed by ordinary GPS
receivers. GPS user receivers are thus able to receive WAAS data in-band and use not only differential corrections,
but also integrity, residual errors and ionospheric information for each monitored satellite.
Figure 2-2 The WAAS Concept
Geostationary
GPS Satellite
Satellite (GEO)
Constellation
L1 & L2
L1
L1 & C-band
Integrity data,
differential corrections,
and ranging control
GPS User
C-band
Wide-area
Wide-area
Wide-area
Reference Station
Reference Station
Reference Station
(WRS)
(WRS)
(WRS)
Ground Uplink
Station
Wide-area
Master Station
(WMS)
(GUS)
Integrity data,
differential corrections,
time control, and status
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Command Descriptions
The signal broadcast via the WAAS GEOs to the WAAS users is designed to minimize modifications to standard
GPS receivers. As such, the GPS L1 frequency (1575.42 MHz) is used, together with GPS-type modulation - e.g.
a Coarse/Acquisition (C/A) pseudorandom (PRN) code. In addition, the code phase timing is maintained close to
GPS time to provide a ranging capability.
2.3.1 WAAS GPSCard
NovAtel has developed several models of WAAS-capable MiLLennium GPSCards that process WAAS signals.
These models can output the WAAS data in log format (FRMA/B, WALA/B), and can incorporate these
corrections to generate differential-quality position solutions. It permits two user-configurable options: 12 GPS (10
Hz position and raw data output rate) or 10 GPS and 1 WAAS L1 channels (2 Hz output). The first configuration
is the default. The second is invoked with the CONFIG command (see Page 86) and resets the card. Standard
WAAS data messages are analysed based on RTCA standard DO-229 Change 1 Minimum Operational
Performance Standards for GPS/WAAS airborne equipment.
A WAAS-capable MiLLennium GPSCard will permit anyone within the area of coverage to take advantage of its
benefits. In addition, it has all the features of a MiLLennium GPSCard.
WAAS COMMANDS
respectively), enable the use of the WAAS corrections in the position filter. By default they are disabled. In order
to use these commands, first issue the following command to put the GPSCard in WAAS mode:
config waascorr
2.4 SPECIAL DATA INPUT COMMANDS
These entries are data messages that are generated by one GPSCard and sent to another. For example, consider a
special configuration in which a GPSCard #1 is able to send these data messages to a GPSCard #2 via a serial port.
For GPSCard #1, this is no different than sending these data messages to a file or a screen. Each of these data
messages has a special header which is interpreted by GPSCard #2 to mean that the data in that message is to be
used as an update of its own GPS parameters such as time, position, velocity, acceleration or knowledge of satellite
ephemeris.
In this general category also belong the RTCM data messages ($RTCM1A, $RTCM3A, $RTCM9A, $RTCM16A,
and $RTCM59A). These are described in further detail in Chapter 4, Message Formats.
The injection of special command data can take place via COM1 or COM2. Remember, the source of these special
data commands are valid NovAtel ASCII data logs.
The special data commands fall into two categories: Almanac Data and Differential Corrections.
2.4.1 Almanac Data
The GPSCard’s standard features include almanac data collection. Following a cold-start boot-up or system reset,
the GPSCard will begin a sky search. Once a valid satellite is acquired, the GPSCard will begin almanac
downloading and decoding. This process will take at least 12.5 minutes following the cold-start (assuming there
are no problems with satellite visibility or the antenna system). It is noted that Ionospheric Correction Data and
UTC data are also collected at the same time as almanac data and will also be available following the 12.5 minutes
collection period mentioned above.
12 channel OEM cards with the SAVECONFIG option will automatically save almanacs in their non-volatile
memory. They will also automatically load the last saved almanac following a cold start or a reset. The card will
save an almanac and ionospheric and UTC data received from a satellite if there is no current data in non-volatile
memory (NVM), or if the GPS week number of the received data is newer than the week number of the data in
NVM. The save will not occur until between 12.5 and 25 minutes have elapsed since the last reset. To check if
almanac data is saved in the NVM of the OEM card, check the "almanac data saved" bit in the receiver status word.
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Command Descriptions
The GPSCard is capable of logging almanac data utilizing the NovAtel-format ASCII log command option ALMA.
Once logged, the data records will precede the header with the $ character (e.g., $ALMA).
There are no specific NovAtel log option commands to independently specify output of ionospheric or UTC
parameters. These parameters will always output following the $ALMA log (identifiable by the headers $IONA and
$UTCA respectively). See Chapter 3 and Appendix D, Page 136 for more information on the ALMA output log
command option.
The GPSCard has the capability to accept injection of previously logged NovAtel-format ASCII almanac data
($ALMA, $IONA, and $UTCA). The GPSCard will interpret this log data as special data input commands. This
provides the user with the advantage of being able to inject recent almanac data following a cold-start or RESET
without having to wait the 12.5 minutes described in above paragraphs.
There are various ways by which this can be accomplished.
•
By connecting the COM1 or COM2 port from one GPSCard (reference) directly to the COM1 or
COM2 port of another GPSCard (remote). The reference card is assumed to be tracking
satellites for some time and can be commanded by the ALMA log command option to output
almanac records to the remote card. The remote card can be assumed to be just powered-up
or RESET and will recognize the $ALMA, $IONA, and $UTCA data as special input commands
and update its almanac tables with this new data.
REMEMBER: When connecting two GPSCard COM ports together, the MESSAGES command option should be
set to "OFF" to prevent inter-card "chatter".
•
The MiLLennium GPSCard can log current almanac data to a PC connected to its COM1 or
COM2 port. Assuming the PC is correctly configured using terminal emulator
communications software, then the PC can redirect the GPSCard almanac log to its disk
storage device. At a later time following a system restart, the GPSCard can have this
almanac.dat file (containing $ALMA, $IONA, and $UTCA records) immediately downloaded
as a special input command for immediate use. Refer to the MiLLEnnium GPSCard Guide
to Installation and Operating manual for more information about interfacing with the OEM
card with a PC. [Note: this procedure will generally not be required with OEM cards as all
12 channel cards now have an almanac save feature built in using non-volatile memory.]
$ALMA...
Use this special data input command to quickly update the GPSCard almanac tables following a system restart. It
is generated from a GPSCard ALMA log and is accepted as the following format:
$ALMA,1,3.55148E-003,552960,744,-7.8174E-009,6.10457691E-002,-1.1820041E+000,
1.90436112E+000,-1.8119E-005,-3.6379E-012,1.45854758E-004,2.65602532E+007,
9.55600E-001,1,0,0*0C
...
(one record for each valid satellite)
...
$ALMA,31,4.90379E-003,552960,744,-7.9660E-009,-3.1044479E+000,6.13853346E-001,
1.92552900E+000,6.67572E-006,3.63797E-012,1.45861764E-004,2.65594027E+007,
9.61670E-001,1,0,0*3F
$IONA...
Use this special data input command to quickly update the GPSCard ionospheric corrections tables following a
system restart (always appended to $ALMA records unless intentionally stripped). This data will ensure that the
initial position solutions computed by the GPSCard are as accurate as possible. It is generated from a GPSCard
ALMA log and is accepted by any GPSCard as the following format:
$IONA,1.0244548320770265E-008,1.4901161193847656E-008,-5.960464477539061E-008,
-1.192092895507812E-007,8.8064000000000017E+004,3.2768000000000010E+004, -
1.966080000000001E+005,-1.966080000000001E+005*02
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Command Descriptions
$UTCA...
Use this special data input command to quickly update the GPSCard Universal Time Coordinated (UTC) parameters
following a system restart (always appended to $ALMA records unless intentionally stripped). The UTC data is
required before the GPSCard can accurately compute UTC time. If not input with $UTCA, it may take up to 12.5
minutes after a reset for the GPSCard to receive current UTCA data. In order to comply with NMEA standards, the
GPSCard will null NMEA log data fields until valid UTC parameters are collected or injected by the $UTCA input
command. This command is generated from a GPSCard ALMA log and is accepted as the following format:
$UTCA,-1.769512891769409E-008,-1.776356839400250E-015,552960,744,755,9,10,5*03
2.4.2 Differential Corrections Data
NovAtel MiLLennium cards can utilize the special data input commands $RTCA and $RTCM. These special data
input commands are utilized by a GPSCard operating as a remote station to accept NovAtel ASCII format
differential corrections. The data is generated by a GPSCard operating as a reference station with intent to be
received by remote stations. To correctly interpret these commands, the remote GPSCard must have its ACCEPT
command option set to "COMMANDS" (default). See Appendix A, Page 66 for further information on differential
positioning.
$PVAA/B XYZ POSITION, VELOCITY AND ACCELERATION
The $PVAA and PVAB data messages contain the receiver’s latest computed position, velocity and acceleration.
These quantities are in rectangular ECEF coordinates based on the centre of the WGS 84 ellipsoid.
When a GPSCard receives this data message, it uses the information to update its own position, velocity and
acceleration parameters. This would only be needed if the GPSCard could not compute its own position, velocity
and acceleration due to signal blockage. This data message helps the receiver reacquire satellites after loss of lock.
The data would aid the receiver channels in the re-acquisition process; thus, the receiver would “follow” the
blocked satellites and re-acquire them much more quickly when they become visible again.
The position, velocity and acceleration status fields indicate whether or not the corresponding data are valid. Only
those messages containing valid data are used by the GPSCard.
NOTE 1: This command is intended for applications involving very high dynamics - where significant position,
velocity and acceleration changes can occur during a signal blockage. This data message helps the
receiver reacquire satellites after loss of lock.
NOTE 2: This is a highly complex function, to be used only by advanced users.
The ASCII $PVAA data message is generated from a PVAA log, and the binary PVAB data message is generated from
a PVAB log. For descriptions of these data messages, please see the description of the PVAA/B logs in Chapter 4,
$PVAA,845,344559.00,-1634953.141,-3664681.855,4942249.361,-0.025,0.140,
0.078,0.000,-0.000,0.000,1,1,1*02
$REPA/B RAW GPS EPHEMERIS DATA
In cases where the receiver does not have an ephemeris for a newly-viewed satellite, these data messages can be
used to reduce the time required to incorporate this satellite into the position solution
The $REPA and REPB data messages contain the raw binary information for subframes one, two and three from the
satellite with the parity information removed. Each subframe is 240 bits long (10 words - 25 bits each) and the log
contains a total 720 bits (90 bytes) of information (240 bits x 3 subframes). This information is preceded by the
PRN number of the satellite from which it originated. This message will not be generated unless all 10 words from
all 3 frames have passed parity.
The ASCII $REPA data message is generated from a REPA log, and the binary REPB data message is generated from
a REPB log. For descriptions of these data messages, please see the description of the REPA/B logs in Chapter 3 and
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Command Descriptions
$REPA,14,8B09DC17B9079DD7007D5DE404A9B2D04CF671C6036612560000021804FD,
8B09DC17B98A66FF713092F12B359DFF7A0254088E1656A10BE2FF125655,
8B09DC17B78F0027192056EAFFDF2724C9FE159675A8B468FFA8D066F743*57[CR][LF]
$RTCA... (RTCAA)
Use this special data input command to directly input NovAtel RTCAA differential corrections data, ASCII format.
The data can be accepted using COM1 or COM2. The differential corrections will be accepted and applied upon
receipt of this special data input command.
The data is generated from a GPSCard RTCAA log and is accepted by a GPSCard remote station as in the following
format:
$RTCA,990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD071AFC7FA0D207D090808C0E
045BACC055E9075271FFB0200413F43FF810049C9DFF8FFD074FCF3C940504052DFB*20
$RTCM...(RTCMA,$RTCM1A,$RTCM3A,$RTCM9A,$RTCM16A,$RTCM59A)
Use this special data input command to directly input RTCMA differential correction data, ASCII format (RTCM data
converted to ASCII hexadecimal, with NovAtel header added). The data can be accepted using COM1 or COM2.
The differential corrections will be accepted and applied upon receipt of this special data input command. See
The data is generated from a GPSCard RTCMA log and is accepted by a GPSCard remote station as in the following
format
$RTCM,664142404E7257585C6E7F424E757D7A467C47414F6378635552427F73577261624278777F
5B5A525C7354527C4060777B4843637C7F555F6A784155597D7F6763507B77496E7F7A6A426F555C
4C604F4E7F467F5A787F6B5F69506C6D6A4C*2B
NOTE : The $RTCAA and $RTCMA commands allow the user to intermix differential corrections along with other
ASCII commands or logs over a single port. (You must, however, ensure that the ACCEPT command
option is set to “COMMANDS”.)
TIP :
The decoding success and status of $RTCA and $RTCM records can be monitored using the CDSA/B data
log. These commands will not generate any reply response from the command interpreter. They will
simply be processed for valid format and checksum and used internally. If there is any problem with
the data, characters missing or checksum fail, the data will be discarded with no warning message.
$TM1A/B RECEIVER TIME OF 1PPS
The $TM1A and TM1B data messages can be used to time-synchronize multiple receivers which are all referencing
the same external oscillator. First, ensure that SETTIMESYNC is enabled. Next, the primary unit must be sending
its 1PPS signal to the MARKIN input of the secondary unit. Third, the two units must be communicating via a COM
port. In this configuration, the user can send the $TM1A log from a primary to a secondary unit, in a manner similar
to that for $ALMA or $UTCA. The secondary unit is then able to compare the time information contained in the log
with that of the 1PPS signal, and set its clock even though it may not be tracking any satellites.
The ASCII $TM1A data message is generated from a TM1A log, and the binary TM1B data message is generated from
a TM1B log. For descriptions of these data messages, please see the description of the TM1A/B logs in Chapter 4,
$TM1A,794,414634.999999966,-0.000000078,0.000000021,-.999999998,0*57[CR][LF]
The $TM1A/B message refers to the 1PPS pulse which has just occurred. In other words TM1A comes after a 1PPS
pulse. The length of the pulse for the 24 channel L1/L2 MiLLennium GPSCard is a normally high, active low pulse
(1 millisecond), where falling edge is reference.
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Data Logs
3 DATA LOGS
3
DATA LOGS
3.1 OUTPUT LOGGING
The GPSCard provides versatility in your logging requirements. You can direct your logs to either COM1 or COM2,
or both ports, as well as combine data types. The GPSCard has four major logging formats:
•
•
•
•
NovAtel Format Data Logs (ASCII/Binary)
NMEA Standard Format Data Logs (ASCII)
RTCM Standard Format Data Logs (Binary)
RTCA Standard Format Data Logs (Binary)
All data types can be logged using several methods of triggering each log event. Each log is initiated using theLOG
command. The LOG command and syntax are listed below.
Syntax:
log [port],datatype,[trigger],[period],[offset],{hold}
Syntax
LOG
Description
Example
LOG
port
COM1 or COM2
COM1
datatype Enter one of the valid ASCII or Binary Data Logs (see later in this chapter and Appendix D, Page 136)
POSA
trigger
Enter one of the following triggers.
ONTIME
ONCE
Immediately logs the selected data to the selected port once. Default if trigger field is left blank.
ONMARK
Logs the selected data when a MARKIN electrical event is detected. Outputs internal buffers
at time of mark - does not extrapolate to mark time. Use MKBA/B for extrapolated position at
time of mark.
ONNEW
Logs the selected data each time the data is new even if the data is unchanged.
Logs the selected data only when the data has changed.
ONCHANGED
ONTIME
[period], [offset]
Immediately logs the selected data and then periodically logs the selected data at a frequency
determined by the period and offset parameters. The logging will continue until an UNLOG
CONTINUOUSLY
Will log the data all the time. The GPSCard will generate a new log when the output buffer
associated with the chosen port becomes empty. The continuously option was designed for
use with differential corrections over low bit rate data links. This will provide optimal record
generationrates. Thenextrecord will not begenerateduntil thelastbyteofthepreviousrecord
is loaded into the output buffer of the UART.
period
offset
Use only with theONTIME trigger. Units for this parameter are seconds. The selected period may be any of the
following values: 0.05, 0.10, 0.20, 0.25, 0.50, 1, 2, 3, ... , 3600 seconds but may be limited by the GPSCard model
and previously requested logs. Selected data is logged immediately and then periodic logging of the data will start at
the next even multiple of the period. If a period of 0.20 sec is chosen, then data will be logged when the receiver time
is at the 0.20, 0.40, 0.60 and the next (0.80) second marks. If the period is 15 seconds, then the logger will log the
data when the receiver time is at even 1/4 minute marks. The same rule applies even if the chosen period is not
divisible into its next second or minute marks. If a period of 7 seconds is chosen, then the logger will log at the
multiples of 7 seconds less than 60, that is, 7, 14, 21, 28, 35, 42, 49, 56 and every 7 seconds thereafter.
60
Use only with the ONTIME trigger. Units for this parameter are seconds. It provides the ability to offset the logging
events from the above startup rule. If you wished to log data at 1 second after every minute you would set the period
to 60 seconds and the offset to 1 second (Default is 0).
1
hold
Will prevent a log from being removed when the UNLOGALL command is issued
HOLD
Example:
log com1,posa,ontime,60,1
If the LOG syntax does not include a trigger type, it will be output only once following execution of the LOG
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Data Logs
command. If trigger type is specified in the LOG syntax, the log will continue to be output based on the trigger
specification. Specific logs can be disabled using the UNLOG command, whereas all enabled logs will be disabled
by using the UNLOGALL command (see Chapter 2, Page 23 and Appendix C, Page 132). All activated logs will be
listed in the receiver configuration status log (RCCA).
3.2 NOVATEL FORMAT DATA LOGS
General
The GPSCard is capable of executing more than 40 NovAtel format log commands. Each log is selectable in ASCII
and Binary formats. The one exception to this rule is the RGE log, which can be logged as RGED. The “D” indicates
a compressed binary format to allow higher speed logging. Any format can be selected individually or
simultaneously over the same COMn ports.
All of the log descriptions are listed in alphabetical order in Appendix D. Each log first lists the ASCII format,
followed by the Binary format description.
ASCII Log Structure
Log types ending with the letter A (or a) will be output in ASCII format (e.g., POSA). The structures of all ASCII
logs follow the general conventions as noted here:
1.
2.
3.
The lead code identifier for each record is '$'.
Each log is of variable length depending on amount of data and formats.
All data fields are delimited by a comma ',' with the exception of the last data field, which is followed by
a * to indicate end of message data.
4.
Each log ends with a hexadecimal number preceded by an asterisk and followed by a line termination us-
ing the carriage return and line feed characters, e.g., *xx[CR][LF]. This 8-bit value is an exclusive OR
(XOR) of all bytes in the log, excluding the '$' identifier and the asterisk preceding the two checksum digits.
Structure:
$xxxx, data field..., data field..., data field...
*xx [CR][LF]
Binary Log Structure
Log types ending with the letter B (or b) will be output in Binary format (e.g., POSB). The structures of all Binary
logs follow the general conventions as noted here:
1.
Basic format of:
Sync
3 bytes
Checksum
Message ID
Message byte count
Data
1 byte
4 bytes unsigned integer
4 bytes unsigned integer
x
2.
The Sync bytes will always be:
Byte
First
Hex
AA
Decimal
170
Second
Third
44
11
68
17
3.
4.
The Checksum is an XOR of all the bytes (including the 12 header bytes) and is initially set to 00.
The Message ID identifies the type of log to follow.
5.
The Message byte count equals the total length of the data block including the header.
NOTE: Maximum flexibility for logging data is provided to the user by these logs. The user is cautioned,
however, to recognize that each log requested requires additional CPU time and memory buffer space.
Too many logs may result in lost data and degraded CPU performance. CPU overload can be monitored
Receiver Self-test Status Codes).
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Data Logs
The following table describes the format types used in the description of binary logs.
Type
Size (bytes) Size (bits)
Description
char
1
8
The char type is used to store the integer value of a member of the representable character
set. That integer value is the ASCII code corresponding to the specified character.
int
4
32
The size of a signed or unsigned int item is the standard size of an integer on a particular
machine. On a 32-bit processor (such as the NovAtel GPSCard), the int type is 32 bits, or 4
bytes. The int types all represent signed values unless specified otherwise. Signed integers
are represented in two’s-complement form. The most-significant bit holds the sign: 1 for
negative, 0 for positive and zero.
double
8
64
The double type contains 64 bits: 1 for sign, 11 for the exponent, and 52 for the mantissa.
Its range is ±1.7E308 with at least 15 digits of precision.
float
4
32
The float type contains 32 bits: 1 for the sign, 8 for the exponent, and 23 for the mantissa.
Its range is ±3.4E38 with at least 7 digits of precision.
Each byte within an int has its own address, and the smallest of the addresses is the address of the int. The byte at
this lowest address contains the eight least significant bits of the doubleword, while the byte at the highest address
contains the eight most significant bits. The following illustration shows the arrangement of bytes within words
and doublewords. Similarly the bits of a "double" type are stored least significant byte first. This is the same data
format used by IBM PC computers.
7
0
char
int
address n
31
15
7
0
23
two’s
complement
n+3
n+2
51 47
n+1
n+5
address n
39
62
55
31
23
0
0
15
7
double
float
Biased
52-bits mantissa
Exponent
S
63
52
n+6
n+7
n+4
n+3 n+2
n+1
address n
22
15
7
0
30
Biased
23-bits mantissa
Exponent
S
23
31
n+2
n+1
address n
n+3
3.3 RTK
After setting up your system and initializing the positioning algorithms, as described in the RTK section of Chapter
1. You can use the logs listed in this section to record the data collected. The low-latency-solution logs (e.g.
PRTKA/B) are recommended for kinematic users, while the matched-solution logs (e.g. RTKA/B) are
recommended for stationary users. For a discussion on low-latency and matched solutions, see the Differential
A matched solution is always a carrier-phase differential solution, and consequently offers the greatest possible
accuracy. A low-latency solution, on the other hand, is the best one that is currently available; the possibilities are
categorized as follows, starting with the one offering the greatest accuracy and precision:
1. Carrier-phase differential solution
2. Pseudorange differential solution
3. Single-point solution
Therefore, if an RTK solution is not available, then a low-latency-solution log will contain a pseudorange
differential solution if it exists. If neither an RTK nor a pseudorange differential solution is available, then a low-
latency-solution log will contain a single-point solution.
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Data Logs
3.4 NMEA FORMAT DATA LOGS
General
The NMEA log structures follow format standards as adopted by the National Marine Electronics Association. The
reference document used is "Standard For Interfacing Marine Electronic Devices NMEA 0183 Version 2.00". For
further information, see Appendix F, Standards and References, Page 233. The following table contains excerpts
from Table 6 of the NMEA Standard which defines the variables for the NMEA logs. The actual format for each
parameter is indicated after its description.
Field Type
Symbol
Definition
Special Format Fields
Status
A
Single character field:
A = Yes, Data Valid, Warning Flag Clear
V = No, Data Invalid, Warning Flag Set
Latitude
llll.ll
Fixed/Variable length field:
degrees|minutes.decimal - 2 fixed digits of degrees, 2 fixed digits of minutes and a variablenumber of
digits for decimal-fraction of minutes. Leading zeros always included for degrees and minutes to
maintain fixed length. The decimal point and associated decimal-fraction are optional if full resolution
is not required.
Longitude
Time
yyyyy.yy
Fixed/Variable length field:
degrees|minutes.decimal - 3 fixed digits of degrees, 2 fixed digits of minutes and a variablenumber of
digits for decimal-fraction of minutes. Leading zeros always included for degrees and minutes to
maintain fixed length. The decimal point and associated decimal-fraction are optional if full resolution
is not required
hhmmss.ss Fixed/Variable length field:
hours|minutes|seconds.decimal - 2 fixed digits of hours, 2 fixed digits of minutes, 2 fixed digits of
seconds and variable number of digits for decimal-fraction of seconds. Leading zeros always included
for hours, minutes and seconds to maintain fixed length. The decimal point and associated decimal-
fraction are optional if full resolution is not required.
Defined field
Some fields are specified to contain pre-defined constants, most often alpha characters. Such a field is
indicated in this standard by the presence of one or more valid characters. Excluded from the list of
allowable characters are the following which are used to indicate field types within this standard:
"A", "a", "c", "hh", "hhmmss.ss", "llll.ll", "x", "yyyyy.yy"
Numeric Value Fields
Variable
numbers
x.x
Variable length integer or floating numeric field. Optional leading and trailing zeros. The decimal point
and associated decimal-fraction are optional if full resolution is not required (example: 73.10 = 73.1 =
073.1 = 73)
Fixed HEX field hh___
Fixed length HEX numbers only, MSB on the left
Information Fields
Variable text
c--c
Variable length valid character field.
Fixed length field of uppercase or lowercase alpha characters
Fixed length field of numeric characters
Fixed length field of valid characters
NOTES:
Fixed alpha field aa___
Fixed number
Fixed text field
xx___
cc___
1.
2.
3.
4.
5.
Spaces may only be used in variable text fields.
A negative sign "-" (HEX 2D) is the first character in a Field if the value is negative. The sign is omitted if value is positive.
All data fields are delimited by a comma (,).
Null fields are indicated by no data between two commas (,,). Null fields indicate invalid or no data available.
The NMEA Standard requires that message lengths be limited to 82 characters.
3.5 GPS TIME VS. LOCAL RECEIVER TIME
All logs report GPS time expressed in GPS weeks and seconds into the week. The time reported is not corrected for
local receiver clock error. To derive the closest GPS time, one must subtract the clock offset shown in the CLKA log
(field 4) from GPS time reported.
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Data Logs
GPS time is based on an atomic time scale. Universal Time Coordinated (UTC) time (reported in NMEA logs) is also
based on an atomic time scale, with an offset of seconds applied to coordinate Universal Time to GPS time. GPS
time is designated as being coincident with UTC at the start date of January 6, 1980 (00 hours). GPS time does not
count leap seconds, and therefore an offset exists between UTC and GPS time. The GPS week consists of 604800
seconds, where 000000 seconds is at Saturday midnight. Each week at this time, the week number increments by
one, and the seconds into the week resets to 0. (See Appendix H, Some Common Unit Conversions, Page 236 for
an example)
3.6 STANDARD LOG TABLES
Table 3-1 lists the logs by function while Table 3-2 is an alphabetical listing of logs. Please see Appendix D, Page
136 for a more detailed description of individual NovAtel and NMEA format logs which are listed alphabetically.
RTCM and RTCA format data logs and receiver-independent RINEX logs will be found in Chapter 4. Special
Pass-Through logs are found in Section 3.8.
Table 3-1 Logs By Function Table
COMMUNICATIONS, CONTROL AND STATUS
Logs
Descriptions
CDSA/B
COM port communications status
Log data from COM1
COM1A/B
COM2A/B
COMnA/B
RCSA/B
Log data from COM2
Pass-through data logs
Receiver self-test status
RTCM16T
RTCM16
NovAtel ASCII format special message
RTCM format special message
GENERAL RECEIVER CONTROL AND STATUS
Descriptions
Logs
PVAA/B
RCCA
Receiver’s latest computed position, velocity and acceleration in ECEF coordinates
Receiver configuration status
RCSA/B
RVSA/B
VERA/B
Version and self-test status
Receiver status
Receiver hardware and software version numbers
POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL
Logs Descriptions
DOPA/B
GGAB
DOP of SVs currently tracking
GPS fix data
GPGGA
GPGLL
GPGRS
GPGSA
GPGST
NMEA, position data
NMEA, position data
NMEA, range residuals
NMEA, DOP information
NMEA, measurement noise statistics
Position at time of mark
Position data
MKPA/B
POSA/B
PRTKA/B
PVAA/B
PXYA/B
RTKA/B
SPHA/B
Computed position
Computed position, velocity and acceleration in ECEF coordinates
Position (Cartesian x,y,z coordinates)
Computed position
Speed and direction over ground
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Data Logs
Table 3-1 Logs By Function Table (continued)
SATELLITE TRACKING AND CHANNEL CONTROL
Descriptions
Logs
ALMA/B
DOPA/B
ETSA/B
GPALM
GPGSA
Current decoded almanac data
DOP of SVs currently tracking
Provides channel tracking status information for each of the GPSCard parallel channels
NMEA, almanac data
NMEA, SV DOP information
GPGSV
NMEA, satellite-in-view information
Raw almanac
RALA/B
RASA/B
RGEA/B/D
SATA/B
SBTA/B
SVDA/B
WRCA/B
Raw GPS almanac set
Satellite range measurements
Satellite specific information
Satellite broadcast data (raw symbols)
SV position (ECEF xyz)
Wide band range correction data (grouped format)
WAYPOINT NAVIGATION
Descriptions
Logs
GPRMB
GPRMC
GPVTG
GPZTG
NMEA, waypoint status
NMEA, navigation information
NMEA, track made good and speed
NMEA, time to destination
Position at time of mark input
Navigation waypoint status
Position data
MKPA/B
NAVA/B
POSA/B
SPHA/B
VLHA/B
Speed and course over ground
Velocity, latency & direction over ground
DIFFERENTIAL REFERENCE STATION
Descriptions
Logs
ALMA/B
CDSA/B
CMR
Current almanac information
COM port data transmission status
Pseudorange and carrier phase data
PAVA/B
RGEA/B/D
RPSA/B
RTCAA/B
RTCM1
Parameters being used in the position averaging process
Channel range measurements
Reference station position and health
Transmits RTCA differential corrections in NovAtel ASCII or Binary
Transmits RTCM SC104 standard corrections
Reference position
RTCM3
RTCM1819
RTCM22
RTCM59
RTCMA/B
SATA/B
Uncorrected carrier phase and pseudorange measurements
Extended reference station parameters
NovAtel format RT-20 observation data
Transmits RTCM information in NovAtel ASCII/binary
Satellite specific information
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Data Logs
Table 3-1 Logs By Function Table (continued)
DIFFERENTIAL REMOTE STATION
Descriptions
Logs
CDSA/B
GPGGA
GGAB
Communication and differential decode status
NMEA, position fix data
NovAtel binary version of GPGGA
Position information
POSA/B
PRTKA/B
RTKA/B
RTKOA/B
SATA/B
SVDA/B
VLHA/B
Computed Position – best available
Computed Position – Time Matched
RTK Output
Satellite specific information
SV position in ECEF XYZ with corrections
Velocity, latency & direction over ground
POST PROCESSING DATA
Descriptions
Logs
BSLA/B
CLKA/B
REPA/B
RGEA/B/D
SATA/B
SVDA/B
Most recent matched baseline expressed in ECEF coords.
Receiver clock offset information
Raw ephemeris information
Satellite and ranging information
Satellite specific information
SV position in ECEF XYZ with corrections
CLOCK INFORMATION, STATUS, AND TIME
Descriptions
Logs
CLKA/B
Receiver clock offset information
1
Current clock-model matrices of the GPSCard
CLMA/B
GPZDA
GPZTG
NMEA, UTC time and date
NMEA, UTC and time to waypoint
Time of mark input
MKTA/B
TM1A/B
Time of 1PPS
1
Intended for advanced users of GPS only.
NAVIGATION DATA
Descriptions
Logs
FRMA/B
RALA/B
RASA/B
RBTA/B
REPA/B
Framed raw navigation data
Raw almanac and health data
Raw almanac set
Satellite broadcast data in raw bits
Raw ephemeris data
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Data Logs
Table 3-2 GPSCard Log Summary
Syntax: log port,datatype,[trigger],[period],[offset],{hold}
NovAtel Format Logs
Datatype
ALMA/B
BSLA/B
Description
Datatype
RASA/B
RCCA
Description
Raw GPS Almanac Set
Decoded Almanac
Baseline Measurement
Receiver Configuration
Raw Ephemeris
CDSA/B
CLKA/B
Communication and Differential Decode Status
Receiver Clock Offset Data
Receiver Clock Model
REPA/B
RGEA/B/D
RPSA/B
RTCAA/B
Channel Range Measurements
CLMA/B
COM1A/B
Reference Station Position and Health
Log data from COM1
RTCA format Differential Corrections with NovAtel
headers
COM2A/B
DOPA/B
ETSA/B
Log data from COM2
Dilution of Precision
RTKA/B
Computed Position - Time Matched
RTK Solution Parameters
RTKOA/B
RTCMA/B
Extended Tracking Status
RTCM Type 1 Differential Corrections with NovAtel
headers
GGAB
Global Position System Fix Data - Binary Format RTCM16T
Special Message
MKPA/B
MKTA/B
NAVA/B
PAVA/B
POSA/B
Mark Position
RVSA/B
SATA/B
SBTA/B
SPHA/B
SVDA/B
Receiver Status
Time of Mark Input
Navigation Data
Satellite Specific Data
Satellite Broadcast Data (Raw Symbols)
Speed and Direction Over Ground
Positioning Averaging Status
Computed Position
SV Position in ECEF XYZ Coordinates with
Corrections
PRTKA/B
PVAA/B
PXYA/B
RALA/B
Computed Position
TM1A/B
VERA/B
Time of 1PPS
XYZ Position, Velocity and Acceleration
Computed Cartesian Coordinate Position
Raw Almanac
Receiver Hardware and Software Version Numbers
Velocity, Latency, and Direction over Ground
Wide Band Range Correcion (Grouped)
VLHA/B
WRCA/B
NMEA Format Logs
GPGSV
GPALM
GPGGA
GPGLL
GPGRS
GPGSA
GPGST
Almanac Data
GPS Satellites in View
Global Position System Fix Data
Geographic Position - lat/lon
GPS Range Residuals for Each Satellite
GPS DOP and Active Satellites
GPRMB
Generic Navigation Information
GPS Specific Information
GPRMC
GPVTG
Track Made Good and Ground Speed
UTC Time and Date
GPZDA
Pseudorange Measurement Noise Statistics
GPZTG
UTC & Time to Destination Waypoint
RTCA Format
RTCA
RTCA Differential Corrections: Type 1 and Type 7
RTCM Format
RTCM1
RTCM3
RTCM9
RTCM16
Type 1 Differential GPS Corrections
Type 3 Reference Station Parameters
Type 9 Partial Satellite Set Differential Corrections
Type 16 Special Message
RTCM1819 Type 18 and Type 19 Uncorrected Carrier Phase and Pseudorange Corrections
RTCM22
RTCM59
Type 22 Extended Reference Station Parameters
Type 59N-0 NovAtel Proprietary Message: RT20 Differential Observations
Note: A/B/D:
A
B
D
refers to GPSCard output logs in ASCII format.
refers to GPSCard output logs in Binary format.
refers to GPSCard output logs in compressed binary format.
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Data Logs
3.7 WAAS
The Wide Area Augmentation System (WAAS) is a safety-critical system that provides a quality of positioning
information previously unavailable. The WAAS improves the accuracy, integrity, and availability of the basic GPS
signals.
3.7.1 WAAS GPSCard Logs
The log WALA/B (see its descriptions on Page 222), provide WAAS satellite-specific data. For more information
3.8 PASS-THROUGH LOGS
The pass-through logging feature enables the GPSCard to redirect any ASCII or binary data that is input at a
specified port (COM1 or COM2) to any specified GPSCard port (COM1 or COM2). This capability, in conjunction with
the SEND command, can allow the GPSCard to perform bi-directional communications with other devices such as
a modem, terminal, or another GPSCard.
There are two pass-through logs COM1A/B and COM2A/B, available on MiLLennium GPSCards.
Pass-through is initiated the same as any other log, i.e., LOG [to-port] [data-type-A/B] [trigger]. However, pass-
through can be more clearly specified as: LOG [to-port] [from-port-A/B] [onchanged]. Now, the [from-port-A/B]
field designates the port which accepts data (i.e., COM1or COM2) as well as the format in which the data will be
logged by the [to-port] — (A for ASCII or B for Binary).
When the [from-port-A/B] field is designated with an [A], all data received by that port will be redirected to the
[to-port] in ASCII format and will log according to standard NovAtel ASCII format. Therefore, all incoming
ASCII data will be redirected and output as ASCII data. However, any binary data received will be converted to a
form of ASCII hexadecimal before it is logged.
When the [from-port-A/B] field is designated with a [B], all data received by that port will be redirected to the [to-
port] exactly as it is received. The log header and time-tag adhere to standard NovAtel Binary Format followed by
the pass-through data as it was received (ASCII or binary).
Pass-through logs are best utilized by setting the [trigger] field as onchanged or onnew. Either of these two
triggers will cause the incoming data to log when any one of the following conditions is met:
•
•
•
•
Upon receipt of a <CR> character
Upon receipt of a <LF> character
Upon receipt of 80 characters
1/2 second timeout following receipt of last character
Each pass-through record transmitted by the GPSCard is time tagged by the GPSCard clock in GPS weeks and
seconds.
For illustration purposes, you could connect two GPSCards together via their COM1 ports such as in a reference
station, labelled as reference station in Figure 5-1, to remote station scenario. If the reference station were logging
PVAA data to the remote station, it would be possible to use the pass-through logs to pass through the received PVAA
differential correction data to a disk file (let's call it DISKFILE.log) at the remote station host PC hard disk.
42
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Data Logs
Figure 3-1 Pass-Through Log Data
A
V
P
A
d
a
$
t
a
l
Data Link
To COM1
To COM1
To COM2
To COM2
fix position (lat,lon,ht,id)
accept com1 none
log com1 pvaa ontime 5
messages com1 off
log console com1a onchanged
Serial Cable
Serial Cable
Host PC
(Rover Station)
Host PC
(Reference Station)
When pass-through logs are being used, the GPSCard’s command interpreter continues to monitor the port for valid
input commands and replies with error messages when the data is not recognized as such. If you do not want the
pass-through input port to respond with error messages during unrecognized data input, see the MESSAGES
command, Appendix C, Page 108 for details on how to inhibit the port’s error message responses. As well, if you
do not want the reference station to accept any input from the remote device, use the ACCEPT NONE command to
disable the port’s command interpreter.
3.8.1 Command Syntax
Syntax:
log
to-port
from-port-A/B
Range Value
trigger
Description
Syntax
Default
unlogall
—
log
—
Log command
to-port
COM1, COM2
Port that will output the pass-through log data
from-port-[A/B] COM1A/B, COM2A/B
Port that will accept input data;
[A] option logs data as ASCII,
—
[B] option logs data with binary header
trigger
onchanged or onnew
log will output upon receipt of:
—
<CR>, <LF>, 80 characters, or 1/2 sec. timeout
Example 1:
log com2 com1a onchanged
3.8.2 ASCII Log Structure
$port ID week
Field # Field type
$port ID
seconds
pass-through data
*xx
[CR][LF]
Data Description
Log header:
Identifies port accepting input data
Example
1
$COM1
2
3
4
week
GPS week number
747
seconds
GPS seconds into the week at time of log 347131.23
pass-through data Data accepted into COM1
(up to 80 characters)
$TM1A,747,347131.000000000,
0.000000058,0.000000024,
-9.000000009,0*78<CR>
5
6
*xx
Checksum
*2E
[CR][LF]
Sentence terminator
[CR][LF]
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Data Logs
Example 1:
$COM1,747,347131.23,$TM1A,747,347131.000000000,0.000000058,0.00000
0024, -9.000000009,0*78<CR>*2E[CR][LF]
$COM1,747,347131.31,<LF>*4F[CR][LF]
$COM1,747,347131.40,Invalid Command Option<LF>*7C[CR][LF]
$COM1,747,347131.42,Com1>Invalid Command Option<LF>*30[CR][LF]
$COM1,747,347131.45,Com1>*0A[CR][LF]
Example 1, above, shows what would result if a GPSCard logged TM1A data into the COM1 port of another
GPSCard, where the accepting card is redirecting this input data as a pass-through log to its COM2 port (log com2
com1a onchanged). Under default conditions the two cards will "chatter" back and forth with the Invalid
Command Option message (due to the command interpreter in each card not recognizing the command prompts
of the other card). This chattering will in turn cause the accepting card to transmit new pass-through logs with the
response data from the other card. To avoid this chattering problem, use the GPSCard MESSAGES command on the
accepting port to disable error reporting from the receiving port command interpreter or if the incoming data is of
no use to the GPSCard, then disable the command interpreter with the ACCEPT NONE command.
If the accepting port’s error reporting is disabled by MESSAGES OFF, the $TM1A data record would pass through
creating two records as follows:
Example 1a:
$COM1,747,347204.80,$TM1A,747,347203.999999957,-
0.000000015,0.000000024,
-9.000000009,0*55<CR>*00[CR][LF]
$COM1,747,347204.88,<LF>*48[CR][LF]
The reason that two records are logged from the accepting card is because the first record was initiated by receipt
of the $TM1A log’s first terminator <CR>. Then the second record followed in response to the $TM1A log’s second
terminator <LF>.
Note that the time interval between the first character received ($) and the terminating <LF> can be calculated by
differencing the two GPS time tags (0.08 seconds). This pass-through feature is useful for time tagging the arrival
of external messages. These messages could be any user-related data. If the user is using this feature for tagging
external events then it is recommended that the command interpreter be disabled so that the GPSCard does not
Example 1b illustrates what would result if $TM1B binary log data were input to the accepting port
(i.e., log com2 com1a onchanged).
Example 1b:
$COM1,747,349005.18,<AA>D<DC1>k<ETX><NUL><NUL><NUL>4<NUL><NUL><NUL>
<EB><STX><NUL><NUL><FE>3M<NAK>A<VT><83><D6>o<82><C3>Z<BE><FC><97>I
<91><C5>iV><7F><8F>O<NUL><NUL><NUL>"<C0><NUL><NUL><NUL><NUL>*6A
As can be seen, the $TM1B binary data at the accepting port was converted to a variation of ASCII hexadecimal
before it was passed through to COM2 port for logging (MESSAGES command set to OFF).
3.8.3 Binary Log Structure
Format:
Message ID =
30 for COM1B; 31 for COM2B
Message byte count = 24 + (length of pass-through data string received (80 maximum))
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
0
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
char
4
Message byte count
Week number
Seconds of week
8
2
3
4
weeks
12
16
seconds
Pass-through data as
received
variable
24 + (variable data)
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Message Formats
4
MESSAGE FORMATS
4
MESSAGE FORMATS
In a NovAtel RTK positioning system, the observations transmitted by a NovAtel reference station to a NovAtel
remote station can be in either a proprietary RTCA Type 7 or a proprietary RTCM Type 59N message format. A
NovAtel Rover station is also able to receive CMR-format messages,Section 4.3, from a non-NovAtel base station.
Table 4-1 illustrates the various combinations of hardware and message formats, together with the positioning
mode (RT-20 or RT-2) which will result when using all-NovAtel devices:
Table 4-1 Positioning Modes
Reference station:
L1
RTCM Type 59N
Reference station: Reference station: Reference station:
L1
L1 & L2
RTCM Type 59N
L1 & L2
RTCA Type 7
RTCA Type 7
Remote station: L1
RT-20
RT-20
RT-20
RT-20
RT-20
RT-20
RT-20
RT-2
Remote station: L1 & L2
The following information can be used to calculate the minimum data throughput required of the communications
data link. Keep in mind that manufacturers of communication equipment add extra bits to each message (e.g. for
error detection), forming an “overhead” that must be taken into account; also, radio transmitting equipment may
have a duty cycle which must also be factored into the calculations. Thus, a “4800 bits per second” radio modem
might actually sustain only 2000 bits per second. Consult the documentation supplied by the manufacturer of your
communications equipment.
4.1 RTCA-FORMAT MESSAGES
NovAtel has defined two proprietary RTCA Standard Type 71 binary-format messages RTCAOBS and
RTCAREF, for reference station transmissions. These can be used with either single or dual-frequency NovAtel
receivers; existing users of RT-20 wishing to switch from RTCM to RTCA message formats will require a software
upgrade. The RTCA message format outperforms the RTCM format in the following ways, among others:
•
•
•
a more efficient data structure (lower overhead)
better error detection
allowance for a longer message, if necessary
RTCAREF and RTCAOBS, respectively, correspond to the RTCM Type 3 and Type 59 logs used in single-
frequency-only measurements. Both are NovAtel-proprietary RTCA Standard Type 7 messages with an ‘N’
primary sub-label.
RTCAOBS TYPE 7
An RTCAOBS (RTCA Reference-Station Satellite Observations) message contains reference station satellite
observation information. It is used to provide range observations to the remote receiver, and should be sent every
1 or 2 seconds. This log is made up of variable-length messages up to 255 bytes long. The maximum number of
bits in this message is [140 + (92 x N)], where N is the maximum number of satellite record entries transmitted.
Using the RTKMODE command, you can define N to be anywhere from 4 to 20; the default value is 12.
1. For further information on RTCA Standard Type 7 messages, you may wish to refer to:
Minnimum Aviation System Performance Standards - DGNSS Instrument Approach System: Special
Category I (SCAT-I), Document No. RTCA/DO-217 (April 19,1995); Appendix A, Page 21.
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Message Formats
RTCAREF TYPE 7
An RTCAREF (RTCA Reference Station Position Information) message contains reference station position
information, and should be sent once every 10 seconds. Each message is 24 bytes (192 bits) long.
If RTCA-format messaging is being used, the optional station id field that is entered using the FIX POSITION
command can be any 4-character string combining numbers and upper-case letters, and enclosed in quotation
marks (e.g. “RW34”). Note that the representation of this string in the log message would be a number within the
range of 266,305 to 15,179,385 as per RTCA notation. The lower bound of 266,305 represents “AAAA” and the
upper bound of 15,179,385 represents “9999”.
RTCA STANDARD LOGS
The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support Differential
Global Navigation Satellite System (DGNSS) Special Category I (SCAT-I) precision instrument approaches. The
RTCA Standard is in a preliminary state. Described below is NovAtel’s current support for this Standard. It is based
on "Minimum Aviation System Performance Standards DGNSS Instrument Approach System: Special Category I
(SCAT-I)" dated August 27, 1993 (RTCA/DO-217).
RTCA
This log enables transmission of RTCA Standard format Type 1 messages from the GPSCard when operating as a
reference station. Before this message can be transmitted, the GPSCard FIX POSITION command must be set. The
RTCA log will be accepted by a GPSCard operating as a remote station over a COM port after an ACCEPT port RTCA
command is issued.
The RTCA Standard for SCAT-I stipulates that the maximum age of differential correction (Type 1) messages
accepted by the remote station cannot be greater than 22 seconds. See the DGPSTIMEOUT command in Chapter 2,
The RTCA Standard also stipulates that a reference station shall wait five minutes after receiving a new ephemeris
before transmitting differential corrections. See the DGPSTIMEOUT command for information regarding ephemeris
delay settings.
The basic SCAT-I Type 1 differential correction message is as follows:
Format:
Field Type
Message length = 11 + (6*obs): (83 bytes maximum)
Data
Bits
Bytes
SCAT-I header
–
–
–
Message block identifier
Reference station ID
Message type
8
24
8
6
2
(this field will always report 00000001)
Message length
–
8
Type 1 header
Type 1 data
–
–
Modified z-count
13
3
Acceleration error bound
(In the GPSCard, this field will report
000)
–
Satellite ID
6
16
8
12
6
1
–
–
Pseudorange correction
6 *obs
Issue of data
1
–
–
Range rate correction
UDRE
CRC
Cyclic redundancy check
3
1
The pseudorange correction and range rate correction fields have a range of ±655.34 meters and ±4.049 m/s respec-
tively. Any satellite which exceeds these limits will not be included.
RTCAA
This log contains the same data available in the RTCA SCAT-I message, but has been modified to allow flexibility
in using the RTCA data. The RTCA data has been reformatted to be available in ASCII hexadecimal, utilizing a
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Message Formats
NovAtel header and terminates with a checksum.
This message was designed so that RTCA data can be intermixed with other NovAtel ASCII data over a common
communications port. The log is not in pure RTCA format. The header ($RTCA) and terminator (*xx) must be
stripped off at the receiving end, then the data will need to be converted from hexadecimal to binary before the
RTCA information is retrieved.
The RTCAA log can be directly decoded by other NovAtel GPSCard receivers operating as remote stations. They
will recognize the $RTCA header as a special data input command and the differential corrections data will be
directly applied. The GPSCard remote station receiving this log must have the ACCEPT command set to "ACCEPT
port COMMANDS".
Structure:
$RTCA data
*xx
[CR][LF]
Field #
Field Type
Data Description
Example
1
2
$RTCA
data
Log header
$RTCA
SCAT-I type 1 differential
corrections
990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9
FD071AFC7FA0D207D090808C0E045BACC055E9075271FFB
0200413F43FF810049C9DFF8FFD074FCF3C940504052DFB
3
4
*xx
Checksum
*20
[CR][LF]
[CR][LF]
Example:
$RTCA,990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD071AFC7FA0
D207D090808C0E045BACC055E9075271FFB0200413F43FF810049C9DFF8FFD074F
CF3C940504052DFB*20[CR][LF]
RTCAB
The RTCAB log contains the SCAT-I differential corrections message with the standard NovAtel binary log preamble
(header) added. The RTCAB log will be accepted by the GPSCard over a COM port after an "ACCEPT port RTCA"
command is issued.
Format:
Field #
Message ID = 38
Message byte count = 12 + (11+(6*obs)): 95 bytes maximum
Bytes Format Offset
char
Data
1
Sync
3
1
4
4
6
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
Message byte count
2
–
–
–
–
Message block identifier
Reference station ID
Message type
12
18
20
Message length
3
4
–
–
Modified z-count
Acceleration error bound
2
6
–
–
–
–
–
Satellite ID
Pseudorange correction
Issue of data
Range rate correction
UDRE
5
6
Next PRN offset = 26 + (6*obs) where obs varies from 0 to (obs-1)
CRC
3
4.2 RTCM-FORMAT MESSAGES
The Radio Technical Commission for Maritime Services (RTCM) was established to facilitate the establishment of
various radio navigation standards, which includes recommended GPS differential standard formats.
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The standards recommended by the Radio Technical Commission for Maritime Services Special Committee 104,
Differential GPS Service (RTCM SC-104,Washington, D.C.), have been adopted by NovAtel for implementation
into the GPSCard. Because the GPSCard is capable of utilizing RTCM formats, it can easily be integrated into
positioning systems around the globe.
As it is beyond the scope of this manual to provide in-depth descriptions of the RTCM data formats, it is
recommended that anyone requiring explicit descriptions of such, should obtain a copy of the published RTCM
RTCM SC-1042 Type 3 & 59 messages can be used for reference station transmissions in differential systems.
However, since these messages do not include information on the L2 component of the GPS signal, they cannot be
used with RT-2 positioning. Regardless of whether single or dual-frequency receivers are used, the RT-20
positioning algorithm would be used. This is for a system in which both the reference and remote stations utilize
NovAtel receivers.
Note that the error-detection capability of an RTCM-format message is less than that of an RTCA-format message.
The communications equipment that you use may have an error-detection capability of its own to supplement that
of the RTCM message, although at a penalty of a higher overhead (see the discussion at the beginning of this
•
RTCM Type 3 Reference Station Position
A Type 3 message contains reference station position information. This message must be sent at least once every
30 seconds, although it is recommended that it be sent once every 10 seconds. It uses four RTCM data words
following the two-word header, for a total frame length of six 30-bit words (180 bits).
•
RTCM Type 59 NovAtel Proprietary (RT-20)
A Type 59N message contains reference station satellite observation information, and should be sent once every 2
seconds. It is variable in size, and can be up to thirty three 30-bit words (990 bits) long.
If RTCM-format messaging is being used, the optional station id field that is entered using the FIX POSITION
command can be any number within the range of 0 - 1023 (e.g. 119). The representation in the log message would
be identical to what was entered.
RTCM General Message Format
All GPSCard RTCM standard format logs adhere to the structure recommended by RTCM SC-104. Thus, all RTCM
message are composed of 30 bit words. Each word contains 24 data bits and 6 parity bits. All RTCM messages
contain a 2-word header followed by 0 to 31 data words for a maximum of 33 words (990 bits) per message
Message Frame Header
Data
Bits
Word 1
–
–
–
–
Message frame preamble for synchronization
Frame/message type ID
reference station ID
8
6
10
Parity
6
Word 2
–
–
–
–
–
Modified z-count (time tag)
Sequence number
Length of message frame
reference station health
Parity
13
3
5
3
6
The remainder of this section will provide further information concerning GPSCard commands and logs that utilize
the RTCM data formats.
2. For further information on RTCM SC-104 messages, you may wish to refer to:
RTCM Recommended Standards for Differential Navstar GPS Service, Version 2.1, RTCM Paper 194-
93/SC104-STD (January 3, 1994)
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Message Formats
RTCM Standard Commands
RTCMRULE
The RTCM standard states that all equipment shall support the use of the "6 of 8" format (data bits a1 through a6
where bits a1 through a6 are valid data bits and bit a7 is set to mark and bit a8 is set to space).
The GPSCard RTCMRULE command allows for flexibility in the use of the bit rule to accommodate compatibility
with equipment that does not strictly adhere to the RTCM stated rule.
Syntax:
RTCMRULE rule
Syntax
RTCMRULE
rule
Range Value
Description
Default
-
Command
6CR
6SP
6CR is for 6 bits of valid data per byte. Each frame is followed by a <CR> character.
6CR
6SP (6 bit special); the RTCM decoder of the remote receiver will ignore the two MSB of the
data and hence all 6 bit data will be accepted. This allows users with non-conforming 6 bit rule
data to use the NovAtel receiver to accept their RTCM data. The user will not be allowed to
enter extra control data such as CR/LF, as this will be treated as RTCM data and cause the
parity to fail. This option does not affect RTCM generation. The output will be exactly the same
as if the RTCMRULE 6 option was chosen. The upper two bits are always encoded as per
RTCM specification.
6
8
6 is for 6 bits of valid data per byte
8 is for 8 bits of valid data per byte
Example:
rtcmrule 6cr
RTCM16T
This is a NovAtel GPSCard command which relates to the RTCM Type 16
This command allows the GPSCard user to set an ASCII text string. Once set, the text string can be transmitted as
standard format RTCM Type 16 data (see the RTCM16 log, Page 53). The text string entered is limited to a maximum
of 90 ASCII characters. This message is useful for a reference station wanting to transmit special messages to
remote users.
The text string set here can be verified by observing the RCCA command configuration log. As well, the message
text can be transmitted as a NovAtel Format ASCII log by utilizing the "LOG port RTCM16T" command.
Syntax:
RTCM16T message
Syntax
RTCM16T
Range Value
Description
Command
ASCII text message
-
message
up to 90 characters
Example:
rtcm16t This is a test of the RTCM16T Special Message.
RTCM Standard Logs
The NovAtel logs which implement the RTCM Standard Format for Type 1, 3, 9, and 16, 18, 19 and 22 messages
are known as the RTCM1 (or RTCM), RTCM3, RTCM9, RTCM16, RTCM1819 and RTCM22 logs, respectively,
while Type 59N-0 messages are listed in the RTCM59 log.
NovAtel has created ASCII and binary versions of each of these logs so that RTCM data can be sent or received
along with other NovAtel ASCII and binary data over a common communications port. As per the usual
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convention, an “A” at the end of the log name denotes the NovAtel ASCII version (e.g. RTCM1A), and a “B”
denotes the NovAtel binary version (e.g. RTCM1B). These logs contain the same data that is available in the
corresponding RTCM Standard Format messages; however, the data has been “packaged” into NovAtel-format
messages.
These NovAtel-format logs are not in pure RTCM SC-104 format and are not directly usable as such. There are
two scenarios which affect how these logs are processed:
Case 1: ASCII messages (RTCMxA)
•
The NovAtel header ($RTCMx) and checksum terminator (*yz) must be stripped off at the
receiving end; then, the data will need to be converted from hexadecimal to binary before
the RTCM information can be retrieved.
•
Provided that the GPSCard that is acting as a remote station has its ACCEPT command set
to “ACCEPT port COMMANDS” (which is the default setting), the receiving GPSCard will
recognize the NovAtel header ($RTCMxA) as a special data input command, and apply the
differential corrections data directly. No extra processing is required.
Case 2: Binary messages (RTCMxB)
•
The 12-byte NovAtel header must be stripped off before the RTCM information can be
retrieved.
•
These binary messages are not presently decoded directly by GPSCards, unlike the ASCII
messages.
ASCII
The format of the NovAtel ASCII version of an RTCM log is as follows:
Structure:
header
rtcm data *xx [CR][LF]
Field #
Field Type
header
Data Description
Example
1
2
NovAtel format ASCII header
$RTCM3
rtcm data
hexadecimal representation of binary-
format RTCM SC104 data
597E7C7F7B76537A66406F49487F79
7B627A7A5978634E6E7C5155444946
3
4
*xx
Checksum
*68
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$RTCM3,597E7C7F7B76537A66406F49487F797B627A7A5978634E6E7C515544494
6*68[CR][LF]
BINARY
The format of the NovAtel binary version of an RTCM log is as follows:
Field #
Data
Bytes
Format
char
Offset
1
Sync
3
1
4
4
0
(header)
Checksum
char
3
Message ID
integer
integer
4
Message byte count
RTCM SC104 data
8
2
variable
12
RTCM OR RTCM1
This is the primary RTCM log used for pseudorange differential corrections. This log follows RTCM Standard Format
for Type 1 messages. It contains the pseudorange differential correction data computed by the reference station
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generating this Type 1 log. The log is of variable length, depending on the number of satellites visible and
pseudoranges corrected by the reference station. Satellite specific data begins at word 3 of the message.
Structure:
(Follows RTCM Standard for Type 1 message)
Type 1 messages contain the following information for each satellite in view at the reference station:
•
•
•
•
Satellite ID
Pseudorange correction
Range-rate correction
Issue of Data (IOD)
When operating as a reference station, the GPSCard must be in FIX POSITION mode before the data can be correctly
logged.
When operating as a remote station, the GPSCard COM port receiving the RTCM data must have its ACCEPT
command set to "ACCEPT port RTCM".
REMEMBER: Upon a change in ephemeris, GPSCard reference stations will transmit Type 1 messages based
on the old ephemeris for a period of time defined by the DGPSTIMEOUT command. After the
timeout, the reference station will begin to transmit the Type 1 messages based on new
ephemeris.
RTCMA or RTCM1A
This log contains the same data available in the RTCM Standard Format Type 1 messages, but has been modified to
allow flexibility in using the RTCM data. The RTCM data has been reformatted to be available in ASCII hexadecimal,
utilizing a NovAtel header and terminates with a checksum.
This message was designed so that RTCM data can be intermixed with other NovAtel ASCII data over a common
communications port. The log is not in pure RTCM SC104 format. The header ($RTCM) and terminator (*xx) must
be stripped off at the receiving end, then the data will need to be converted from hexadecimal to binary before the
RTCM information is retrieved. The RTCM data is further defined by the RTCM rule (see the RTCMRULE command,
Page 114).
The RTCMA log can be directly decoded by other NovAtel GPSCard receivers operating as remote stations. They
will recognize the $RTCM header as a special data input command and the differential corrections data will be
directly applied. The GPSCard remote station receiving this log must have the ACCEPT command set to "ACCEPT
port COMMANDS".
Structure:
$RTCM
rtcm data *xx [CR][LF]
Field #
Field Type
$RTCM
Data Description
Example
1
2
NovAtel format ASCII header
$RTCM
rtcm data
hexadecimal representation of binary 664142406B61455F565F7140607E5D526A5366C7
format RTCM SC104 data
C7F6F5A5B766D587D7F535C4B697F54594060685
652625842707F77555B766558767F715B7746656B
3
4
*xx
Checksum
*54
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$RTCM,664142406B61455F565F7140607E5D526A5366C7C7F6F5A5B766D587D7F535C4B697F54594
060685652625842707F77555B766558767F715B7746656B*54[CR][LF]
RTCMB or RTCM1B
This log contains the same data available in the RTCM Standard Format Type 1 messages, but has been modified to
allow flexibility in using the RTCM data. The RTCM data has been reformatted to be available in NovAtel Binary
Format, utilizing a NovAtel binary header.
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This message was designed so that RTCM data can be transmitted intermixed with other NovAtel binary data over
a common communications port. The log is not in pure RTCM SC104 format and is not directly usable as such.
GPSCard remote receivers cannot decode or interpret the RTCMB data (however, the GPSCard can directly interpret
RTCM and RTCMA). The 12 byte NovAtel binary header must be stripped off before the RTCM information can be
retrieved. The RTCM data is further defined by the RTCM rule (see the RTCMRULE command).
REMEMBER: Ensure that the RTCM rule is the same between all equipment.
Format:
Message ID = 10
Data Bytes
Message byte count = variable
Format Offset
char
Field #
1
Sync
3
0
(header)
Checksum
1
char
3
Message ID
4
integer
integer
4
Message byte count
RTCM SC104 data
4
8
2
variable
12
RTCM1A
Example:
$RTCM,597E7D7F716F745A647D7E42405273505276777C7F736C514E7D477A7F7F
5A7E6E62675F406C567F6753725B675F7B436A646A7D787F675D4A505056687C6B
567C7F5B69796F40547F73595557555546*51[CR][LF]
RTCM1B
Message ID = 10
Message byte count = variable
RTCM3
REFERENCE STATION PARAMETERS
RTK
This log contains the GPS position of the reference station expressed in rectangular ECEF coordinates based on
the center of the WGS84 ellipsoid. This log uses four RTCM data words following the two-word header, for a total
frame length of six 30 bit words (180 bits maximum).
Structure:
(Follows the RTCM SC-104 Standard for a Type 3 message)
Type 3 messages contain the following information:
•
•
•
•
Scale factor
ECEF X-coordinate
ECEF Y-coordinate
ECEF Z-coordinate
The GPSCard only transmits the RTCM Type 3 message (RTCM3) when operating as a reference station paired
with GPSCard remote receivers operating in RT-20 Carrier Phase Mode (see Appendix A, Page 62 for more
information) or for RT-2, periodically transmitting an RTCM Type 18 and RTCM Type 19 (RTCM1819), or
NOTE: This log is intended for use when operating in RT-20 mode.
Example:
$RTCM3,597E7C7F7B76537A66406F49487F797B627A7A5978634E6E7C5155444946*68[CR][LF]
RTCM3B
Message ID = 41
Message byte count = 35 if RTCMRULE = 8 (12 bytes header, 23 bytes data)
= 42 if RTCMRULE = 6 (12 bytes header, 30 bytes data)
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RTCM9
PARTIAL SATELLITE SET DIFFERENTIAL CORRECTIONS
RTCM Type 9 messages follow the same format as Type 1 messages. However, unlike Type 1 messages, Type
9’s do not require a complete satellite set. This allows for much faster differential correction data updates to the
remote stations, thus improving performance and reducing latency.
Type 9 messages should give better performance when SA rate correction variations are high, or with slow or noisy
data links.
NOTE: The reference station transmitting the Type 9 corrections must be operating with a high-stability
clock to prevent degradation of navigation accuracy due to the unmodeled clock drift that can occur
between Type 9 messages.
NovAtel recommends a high-stability clock such as the PIEZO Model 2900082 whose 2-sample (Allan)
variance meets the following stability requirements:
3.24 x 10-24 s2/s2 between 0.5 - 2.0 seconds, and
1.69 x 10-22 T s2/s2 between 2.0 - 100.0 seconds
An external clock such as an OCXO requires approximately 10 minutes to warm up and become fully
stabilized after power is applied; do not broadcast RTCM Type 9 corrections during this warm-up period.
Structure: (Follows the RTCM Standard SC-104 for a Type 1 message)
Type 9 messages contain the following information for a group of three satellites in view at the reference station:
•
•
•
•
•
•
Scale factor
User Differential Range Error
Satellite ID
Pseudorange correction
Range-rate correction
Issue of Data (IOD)
RTCM9A
Example:
$RTCM9,66516277547C71435D797760704260596876655F7743585D547562716D7
57E686C5258*6D[CR][LF]
RTCM9B
Message ID = 42
Message byte count = variable
RTCM16
SPECIAL MESSAGE
This log contains a special ASCII message that can be displayed on a printer or cathode ray tube. The GPSCard
reference station wishing to log this message out to remote stations must use the RTCM16T command to set the
required ASCII text message. Once set, the message can then be issued at the required intervals with the “LOG
port RTCM16 interval” command. If it is desired that only updated text messages be transmitted, then the GPSCard
log interval must be either “onnew” or “onchanged”. The Special Message setting can be verified in the RCCA
configuration log.
The RTCM16 data log follows the RTCM Standard Format. Words 1 and 2 contain RTCM header information
followed by words 3 to n (where n is variable from 3 to 32) which contain the special message ASCII text. Up to
90 ASCII characters can be sent with each RTCM Type 16 message frame.
Structure: (Follows the RTCM Standard SC-104 for a Type 16 message)
RTCM16A
This message is the hexadecimal code equivalent of the special message entered using the RTCM16T command.
Example:
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$RTCM16,6649404045495E5A5C406A58696D76596D5F665F765869694D4E53604D
70696552567E7B675762747B67576C574E596F59697146555A75516F5F667D4967
5656574E53604D55565A6D69647B67777E454659685D56465A67616E4B7E7F7F7D
*52[CR][LF]
RTCM16B
This message is the binary code equivalent of the special message entered using the RTCM16T command.
Message ID = 43
Message byte count = variable
RTCM16T
This message is used at the remote station to report the contents of a Type 16 message that was received from the
reference station.
Structure:
$RTCM16T ASCII Special Message of up to 90 characters *xx [CR][LF]
Example:
$RTCM16T,Time flies like an arrow; fruit flies like a banana.*1F[CR][LF]
RTCM1819 UNCORRECTED CARRIER PHASE AND PSEUDORANGE
MEASUREMENTS
RTK
This log contains the raw carrier phase raw pseudorange measurement information. The measurements are not
corrected by the ephemerides contained in the satellite message. Word 3, the first data word after the header,
contains a GPS TIME OF MEASUREMENT field which is used to increase the resolution of the MODIFIED Z-
COUNT in the header. Word 3 is followed by pairs of words containing the data for each satellite observed.
Appropriate flags are provided to indicate L1, L2, ionospheric free pseudorange or ionospheric diffeerence carrier
phase data, C/A or P-code, and half or full-wave L2 carrier phase measuurements. The carrier smoothing interval
for pseudoranges and pseudorange corrections is also furnished, for a total frame length of six 30 bit words (180
bits maximum).
Structure:
(Follows the RTCM SC-104 Standard for a Type 18 and Type 19 message)
For RT-2, you may periodically transmit an RTCM Type 18 and RTCM Type 19 (RTCM1819) together with an
RTCM22 RTCM EXTENDED REFERENCE STATION PARAMETERS
RTK
Message Type 22 provides firstly, a means of achieving sub-millimeter precision for base station coordinates in a
kinematic application, and secondly, base station antenna height above a base, which enables mobile units to
reference measured position to the base directly in real time.
The first data word of message Type 22 provides the corrections to be added to each ECEF coordinate. Note that
the corrections may be positive or negative.
The second data word, which may not be transmitted, provides the antenna L1 phase center height expressed in
integer and fractional centimeters, and is always positive. It has the same resolutions as the corrections. The range
is about 10 meters. The spare bits can be used if more height range is required.
RTCM59 TYPE 59N-0 NOVATEL PROPRIETARY MESSAGE
RTK
RTCM Type 59 messages are reserved for proprietary use by RTCM reference station operators.
Each message is variable in length, limited only by the RTCM maximum of 990 data bits (33 words maximum).
The first eight bits in the third word (the word immediately following the header) serve as the message
identification code, in the event that the reference station operator wishes to have multiple Type 59 messages.
NovAtel has defined only a Type 59N-0 message to date; it is to be used for operation in GPSCard receivers
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capable of operating in RT-20 Carrier Phase Differential Positioning Mode. This log is primarily used by a
GPSCard reference station to broadcast its RT-20 observation data (delta pseudorange and accumulated Doppler
range) to remote RT-20 – capable GPSCard receivers.
NOTE 1: The CDSA/B log is very useful for monitoring the serial data link, as well as differential data decode
success.
NOTE 2: This log is intended for use when operating in RT-20 mode.
RTCM59A
Example:
$RTCM59,665D43406E76576561674D7E7748775843757D4E646B545365647B7F48
657F504D4D6D425B657D5858606B617A737F7F7F464440727D7156577C65494F4D
4A60497F414D7E4272786D55534362406144705D764D596A7340654B6D5B464375
5848597C52705779466C*57[CR][LF]
RTCM59B
Message ID = 44
Message byte count = variable
RTCM RECEIVE ONLY DATA
The following RTCM data types can be received and decoded by the GPSCard, however these log types are no
longer transmitted.
RTCM TYPE 2
Quite often a reference station may have new ephemeris data before remote stations have collected the newer
ephemeris. The purpose of Type 2 messages is to act as a bridge between old and new ephemeris data. A reference
station will transmit this Type 2 bridge data concurrently with Type 1’s for a few minutes following receipt of a
new ephemeris. The remote station adds the Type 2 data (delta of old ephemeris minus new ephemeris) to the Type
1 message data (new ephemeris) to calculate the correct pseudorange corrections (based on the old ephemeris).
Once the remote receiver has collected its own updated ephemeris, it will no longer utilize the Type 2 messages.
The GPSCard will accept and decode RTCM Standard Type 2 messages, when available and if required. However,
the GPSCard no longer transmits Type 2 messages.
Type 2 messages are variable in length, depending on the number of satellites being tracked by the reference
station.
4.3 CMR FORMAT MESSAGING
The Compact Measurement Record (CMR) message format was developed by Trimble Navigation Ltd. as a
proprietary data transmission standard for use in real-time kinematic applications. In 1996 Trimble publicly
disclosed this standard and allowed its use by all manufacturers in the GPS industry3.
The NovAtel implementation allows a NovAtel rover receiver to operate in either RT-2 or RT-20 mode while
receiving pseudorange and carrier phase data via CMR messages (version 3.0) from a non-NovAtel base-station
receiver. The MiLLennium can also transmit CMR messages (versions 1.0, 2.0 or 3.0). The station ID, see Page
NOTE: No guarantee is made that the MiLLennium will meet its performance specifications if non-NovAtel
equipment is used.
3. Talbot, N.C. (1996), “Compact Data Transmission Standard for High-Precision GPS”. Proceeding of
the ION GPS-96 Conference, Kansas City, MO, September 1996, Vol. I, pp. 861-871
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Using RT-2 or RT-20 with CMR Format Messages
To enable receiving CMR messages, follow these steps:
1. Issue the COMn command to the rover receiver to set its serial port parameters to the proper bit rate, parity,
2. Issue the “ACCEPT COMn CMR” command to the rover receiver, where “COMn” refers to either the COM1 or
COM2 serial port that is connected to the data link.
Assuming that the base station is transmitting valid data, your rover receiver will now begin to operate in RT-2 or
RT-20 mode. To send CMR messages, do the following:
Periodically transmit two CMR messages at the reference station (the station ID, see Page 98, must be ≤ 31):-
•
A CMROBS message contains reference station satellite observation information, and
should be sent once every 1 or 2 seconds.
•
A CMRREF message contains reference station position information, and should be sent
once every 10 seconds.
In addition to the logs which you can use to output the rover’s position (e.g. POSA/B, PRTKA/B, RTKA/B), the
baseline (BSLA/B), and the reference station’s position and health (RPSA/B), you can also monitor the status of
the incoming CMR messages using the CDSA/B (Communication and Differential Decode Status) log. See Page
144 for a complete description of the CDSA/B log and its arguments.
4.4 RINEX FORMAT
The Receiver-Independent Exchange (RINEX) format is a broadly-accepted, receiver-independent format for
storing GPS data. It features a non-proprietary ASCII file format that can be used to combine or process data
generated by receivers made by different manufacturers. RINEX was originally developed at the Astronomical
Institute of the University of Berne. Version 2, containing the latest major changes, appeared in 1990;
subsequently, minor refinements were added in 1993. To date, there are three different RINEX file types. Each
of the file types consists of a header section and a data section, and includes the following information4:
•
•
observation files (carrier-phase measurements; pseudorange / code measurements; times
of observations)
broadcast navigation message files (orbit data for the satellites tracked; satellite clock
parameters; satellite health condition; expected accuracy of pseudorange measurements;
parameters of single-frequency ionospheric delay model; correction terms relating GPS
time to UTC)
•
meteorological data files (barometric pressure; dry air temperature; relative humidity;
zenith wet tropospheric path delay; time tags)
NOTE: Although RINEX is intended to be a receiver-independent format, there are many optional records and
fields. Please keep this in mind when combining NovAtel and non-NovAtel RINEX data.
In support of the first two file types, NovAtel has created six ASCII log types that contain data records in RINEX
format (XOBS, XOHD, XNAV, XNHD, XKIN, and XSTA). A seventh pseudo-log type (RINEX) can be used
instead to simplify data collection. These logs produce multiple lines of output; each line ends with a NovAtel
checksum. Once collected these logs should be processed into the 2 standard RINEX files using NovAtel’s Convert
utility.
A sample session, illustrating the use of the commands and logs, would be as follows:
4. For further information on RINEX Version 2 file descriptions, you may wish to consult relevant articles
in scientific journal such as:
Gurtner, W.G. Mader (1990): “Receiver Independent Exchange Format Version 2.” CSTG GPS
Bulletin Vol. 3 No. 3, Sept/Oct 1990, National Geodetic Survey, Rockville.
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Message Formats
COM1> log com2 rinex ontime 30
(some time later - move to a new site)
COM1> log com2 xkin
COM1> rinex markernum 980.1.35
COM1> rinex antdh 3.1
(at new site)
COM1> log com2 xsta
(some time later - logging complete)
COM1> unlogall
It should be noted that the first line of this example is equivalent to these two lines:
COM1> log com2 xobs ontime 30
COM1> log com2 xnav onchanged
The use of the pseudo-log RINEX is for convenience only.
After the UNLOGALL command, the XNHD and XOHD logs are automatically generated if XNAV and XOBS,
respectively, were active.
4.4.1 COMMANDS
RINEX
This command is used to configure the user-defined fields in the file headers.
The settings of all these fields are visible in the RCCA log. All settings can be saved to non-volatile memory on a
MiLLennium card by the SAVECONFIG command. A CRESET command will empty all text fields and reduce to
zero the antenna offsets.
Syntax:
RINEX
cfgtype
Range Values
Command
RINEX
Description
-
Command
cfgtype
AGENCY
ANTDE
Define agency name in observation log header
Define antenna delta east (offset to marker) in observation log and static event log
Define antenna delta height (offset to marker) in observation log and static event log
Define antenna delta north (offset to marker) in observation log and static event log
Define antenna number in observation log header
ANTDH
ANTDN
ANTNUM
ANTTYPE
COMMENT
MARKNAME
MARKERNUM
OBSERVER
RECNUM
Define antenna type in observation log header
Add comment to navigation and observation log headers (optional)
Define marker name in observation log and static event log
Define marker number in observation log (optional) and static event log
Define observer name in observation log header
Define receiver number in observation log header
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Message Formats
Command example:
COM1> rinex agency NovAtel Surveying Service Ltd.
COM1> rinex antde -0.05
COM1> rinex antdh 2.7
COM1> rinex antdn 0.1
COM1> rinex antnum Field #1
COM1> rinex anttype NovAtel 501
COM1> rinex comment Field trial of new receiver
COM1> rinex markname A980
COM1> rinex markernum 980.1.34
COM1> rinex observer S.C. Lewis
COM1> rinex recnum LGN94100019
COM1> log com1 rcca
Log example:
$RCCA,COM1,9600,N,8,1,N,OFF,OFF*65
... etc....
$RCCA,RINEX,COMMENT,Field trial of new receiver*68
$RCCA,RINEX,AGENCY,NovAtel Surveying Service Ltd.*5A
$RCCA,RINEX,MARKNAME,A980*15
$RCCA,RINEX,MARKERNUM,980.1.34*24
$RCCA,RINEX,OBSERVER,S.C. Lewis*0B
$RCCA,RINEX,RECNUM,LGN94100019*34
$RCCA,RINEX,ANTNUM,Field #1*0A
$RCCA,RINEX,ANTTYPE,NovAtel 501*4B
$RCCA,RINEX,ANTDN,0.100*09
$RCCA,RINEX,ANTDE,-0.050*2B
$RCCA,RINEX,ANTDH,2.700*0B
Note that the RCCA log shows any non-default RINEX settings.
4.4.2 LOGS
RINEX OBSERVATION AND NAVIGATION LOGS AND HEADERS
This pseudo - log type exists to simplify the commands for the user. For example, at the command
COM1> log com2 rinex ontime 30
the XOBS and XNAV logs are both started. When it is time to cease data collection, the command
COM1> unlog com2 rinex
or
COM1> unlogall
will stop the XOBS and XNAV logs, and the XNHD and XOHD logs will be generated once.
XKIN OBSERVATION KINEMATIC EVENT
This log generates a time tag and flag to indicate when antenna motion begins.
Command example:
COM1> log com2 xkin
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Message Formats
Log example:
$XOBS, 96 04 10 17 25 19.5000000 2*00
$XOBS,
4
1*2F
$XOBS, *** KINEMATIC DATA FOLLOWS ***
COMMENT*50
XNAV NAVIGATION DATA RECORD
This log type contains broadcast navigation message records for each satellite being used. Each set of records
consists of:
•
•
•
•
•
•
orbit data for the satellites tracked
satellite clock parameters
satellite health condition
expected accuracy of pseudorange measurements
parameters of single-frequency ionospheric delay model
correction terms relating GPS time to UTC
Command example:
COM1> log com2 xnav onchanged
Log example:
$XNAV,22 96 04 10 18 00
0.0 .2988767810166D-03 .2842170943040D-11 .0000000000000D+00*77
$XNAV,.1570000000000D+03 .5162500000000D+02 .4851987819054D-08 -.307153354042D+01*10
$XNAV,.2656131982803D-05.8917320519686D-02.9054318070412D-05 .5153725172043D+04*01
$XNAV, .3240000000000D+06 -.149011611938D-06
.1649994199967D+01
.4627841719040D-01
.8480000000000D+03
.1117587089539D-07*1E
-.806355016494D-08*17
.0000000000000D+00*18
$XNAV,.9465553285374D+00
$XNAV,-.175721605224D-09
.1992812500000D+03
.1000000000000D+01
$XNAV,.7000000000000D+01 .0000000000000D+00 .1396983861923D-08 .4130000000000D+03*08
$XNAV,.3170760000000D+06*5E
XNHD NAVIGATION HEADER
This log consists of a RINEX-format header for broadcast navigation message files. It can be generated at any
point, using a command such as
COM1> log com2 xnhd
or it will be generated automatically when logging is complete, using a command such as
COM1> unlogall
Log example:
$XNHD,
$XNHD, NovAtel GPSCard
$XNHD,Field trial of new receiver
2
NAVIGATION DATA
96-04-10 16:13
COMMENT*29
RINEX VERSION / TYPE*3B
PGM / RUN BY / DATE*05
NATIVE
$XNHD,.10245D-07
$XNHD,.88064D+05
.14901D-07 -.5960D-07 -.1192D-06 ION ALPHA*05
.32768D+05 -.1966D+06 -.1966D+06 ION BETA*46
$XNHD,
$XNHD,
$XNHD,
.9313225746155D-09
11
-.799360577730D-14
503808
848
DELTA-UTC: A0,A1,T,W*3C
LEAP SECONDS*4D
END OF HEADER*6F
XOBS OBSERVATION DATA RECORD
This log contains observation records, which include the following information:
•
•
•
•
Times of observations
Carrier-phase measurements
Pseudorange (code) measurements
Doppler measurements
A set of observation records is generated at the end of every time interval specified.
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Message Formats
Command example:
COM1> log com2 xobs ontime 5
Log example:
$XOBS, 96 04 10 16 12 45.0000000 0 10G22G29G 3G28G16G27G 2G18G31G19*2B
$XOBS,
$XOBS,
$XOBS,
$XOBS,
$XOBS,
$XOBS,
$XOBS,
$XOBS,
$XOBS,
$XOBS,
25589487.514 1
24031521.036 7
22439789.377 9
22766999.777 9
23387648.507 6
21889019.606 8
24678340.269 7
21218703.216 9
21855014.913 9
20157467.672 9
134473357.195 11
126285967.262 7
117921029.600 9
119640447.360 9
122901958.756 6
115027300.270 8
129684455.444 7
111503905.438 9
114847991.342 9
105927196.398 9
3689.020 1*20
3673.582 7*3E
270.081 9*2A
924.831 9*28
-640.482 6*2F
-2682.420 8*3D
-3295.920 7*3D
2528.269 9*30
-1951.670 9*33
-688.169 9*2B
XOHD OBSERVATION HEADER
This log consists of a RINEX-format header for observation message files. It can be generated at any point, using
a command such as
COM1> log com2 xohd
or it will be generated automatically when logging is complete, using a command such as
COM1> unlogall
Log example:
$XOHD,
$XOHD,NovAtel GPSCard
$XOHD,Field trial of new receiver
$XOHD,A980
2
OBSERVATION DATA
NATIVE
G (GPS)
96-04-10 16:04
RINEX VERSION / TYPE*50
PGM / RUN BY / DATE*02
COMMENT*08
MARKER NAME*62
$XOHD,980.1.34
MARKER number*11
$XOHD,S.C. Lewis
$XOHD,LGN94100019
$XOHD,Field #1
NovAtel Surveying Service Ltd.
OBSERVER / AGENCY*49
REC # / TYPE / VERS*5F
ANT # / TYPE*77
GPSCard-2 FRASER
3.41RC12
NovAtel 501
$XOHD, -1634937.3828 -3664677.1214 4942285.1723
APPROX POSITION XYZ*67
ANTENNA: DELTA H/E/N*56
$XOHD,
$XOHD,
$XOHD,
$XOHD,
$XOHD,
2.7000
0.0500 0.1000
1 0 7 G 2 G 3 G16 G18 G19 G22 G27 WAVELENGTH FACT L1/2*2D
1 0 3 G28 G29 G31
3 C1 L1 D1
WAVELENGTH FACT L1/2*28
# / TYPES OF OBSERV*0F
INTERVAL*3D
5
$XOHD, 1996 4 10
$XOHD, 1996 4 10
16
16
4
43.150000
0.000000
TIME OF FIRST OBS*03
TIME OF LAST OBS*56
# OF SATELLITES*14
PRN / # OF OBS*45
PRN / # OF OBS*44
PRN / # OF OBS*50
PRN / # OF OBS*5E
PRN / # OF OBS*5F
PRN / # OF OBS*57
PRN / # OF OBS*52
PRN / # OF OBS*5D
PRN / # OF OBS*5C
PRN / # OF OBS*55
END OF HEADER*6E
13
$XOHD,
10
$XOHD, G 2 101 101
$XOHD, G 3 101 101
$XOHD, G16 101 101
$XOHD, G18 101 101
$XOHD, G19 101 101
$XOHD, G22 101 101
$XOHD, G27 101 101
$XOHD, G28 101 101
$XOHD, G29 101 101
$XOHD, G31 101 101
$XOHD,
101
101
101
101
101
101
101
101
101
101
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Message Formats
XSTA OBSERVATION STATIC EVENT
This log generates a time tag and flag when a new site occupation begins.
Command example:
COM1> log com2 xsta
Log example:
$XOBS, 96 04 10 17 25 45.0000000 3 4*39
$XOBS,A980
$XOBS,980.1.35
MARKER NAME*7F
MARKER number*0D
ANTENNA: DELTA H/E/N*4C
COMMENT*19
$XOBS,
3.1000
0.0500
0.1000
$XOBS, *** NEW SITE OCCUPATION ***
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A
GPS Overview
A
GPS OVERVIEW
A
GPS OVERVIEW
The Global Positioning System (GPS) is a satellite navigation system capable of providing a highly accurate,
continuous global navigation service independent of other positioning aids. GPS provides 24-hour, all-weather,
worldwide coverage with position, velocity and timing information.
The system uses the NAVSTAR (NAVigation Satellite Timing And Ranging) satellites which consists of 24
operational satellites to provide a GPS receiver with a six to twelve-satellite coverage at all times depending on the
model. A minimum of four satellites in view allows the GPSCard to compute its current latitude, longitude, altitude
with reference to mean sea level and the GPS system time.
Figure A-1 NAVSTAR Satellite Orbit Arrangement
A.1 GPS SYSTEM DESIGN
The GPS system design consists of three parts:
•
•
•
The Space segment
The Control segment
The User segment
All these parts operate together to provide accurate three dimensional positioning, timing and velocity data to users
worldwide.
The Space Segment
The space segment is composed of the NAVSTAR GPS satellites. The final constellation of the system consists of 24
satellites in six 55° orbital planes, with four satellites in each plane. The orbit period of each satellite is
approximately 12 hours at an altitude of 10,898 nautical miles. This provides a GPS receiver with six to twelve
satellites in view from any point on earth, at any particular time.
The GPS satellite signal identifies the satellite and provides the positioning, timing, ranging data, satellite status and
the corrected ephemerides (orbit parameters) of the satellite to the users. The satellites can be identified either by
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GPS Overview
the Space Vehicle Number (SVN) or the Pseudorandom Code Number (PRN). The PRN is used by the NovAtel
GPSCard.
The GPS satellites transmit on two L-band frequencies; one centered at 1575.42 MHz (L1) and the other at 1227.60
MHz (L2). The L1 carrier is modulated by the C/A code (Coarse/Acquisition) and the P code (Precision) which
is encrypted for military and other authorized users. The L2 carrier is modulated only with the P code.
The Control Segment
The control segment consists of a master control station, five reference stations and three data up-loading stations
in locations all around the globe.
The reference stations track and monitor the satellites via their broadcast signals. The broadcast signals contain the
ephemeris data of the satellites, the ranging signals, the clock data and the almanac data. These signals are passed
to the master control station where the ephemerides are re-computed. The resulting ephemerides corrections and
timing corrections are transmitted back to the satellites via the data up-loading stations.
The User Segment
The user segment, such as the NovAtel GPSCard receiver, consists of equipment which tracks and receives the
satellite signals. The user equipment must be capable of simultaneously processing the signals from a minimum of
four satellites to obtain accurate position, velocity and timing measurements. A user can also use the data provided
by the satellite signals to accomplish specific application requirements.
A.2 HEIGHT RELATIONSHIPS
What is a geoid?
The equipotential surface which best represents mean sea-level where an equipotential surface is any surface where
gravity is constant. This surface not only covers the water but is projected throughout the continents. Most surfaces
in North America use this surface as its zero value, i.e. all heights are referenced to this surface.
What is an ellipsoid?
An ellipsoid, also known as a spheroid, is a mathematical surface which is sometimes used to represent the earth.
Whenever you see latitudes and longitudes describing the location, this coordinate is being referenced to a specific
ellipsoid. GPS positions are referred to an ellipsoid known as WGS84 (World Geodetic System of 1984).
What is the relationship between a geoid and an ellipsoid?
The relationship between a geoid and an ellipsoid is shown in Figure A-2.
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GPS Overview
Figure A-2 Illustration of GPSCard Height Measurements
Notes:
References:
h = H + N
N = h - H
1
2
3
Topography
Geoid (mean sea level)
Spheroid (ellipsoid)
H = GPSCard computed height above/below geoid
N = Geoidal Height (undulation)
h = GPS system computed height above the spheroid
From the above diagram, and the formula h = H + N, to convert heights between the ellipsoid and geoid we require
the geoid-ellipsoid separation value. This value is not easy to determine. A world-wide model is generally used to
provide these values. NovAtel GPS receivers store this value internally. This model can also be augmented with
local height and gravity information. A more precise geoid model is available from government survey agencies
e.g. U.S. National Geodetic Survey or Geodetic Survey of Canada (refer to Appendix F, Standards and References).
Why is this important for GPS users?
The above formula is critical for GPS users as they typically obtain ellipsoid heights and need to convert these into
mean sea-level heights. Once this conversion is complete, users can relate their GPS derived heights to more
“usable” mean sea-level heights.
A.3 GPS POSITIONING
GPS positioning can be categorized as follows:
1. single-point or relative
2. static or kinematic
3. real-time or post-mission data processing
A distinction should be made between accuracy and precision. Accuracy refers to how close an estimate or
measurement is to the true but unknown value; precision refers to how close an estimate is to the mean (average)
estimate. Figure A-3 illustrates various relationships between these two parameters: the true value is "located" at
the intersection of the cross-hairs, the centre of the shaded area is the "location" of the mean estimate, and the radius
of the shaded area is a measure of the uncertainty contained in the estimate.
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GPS Overview
Figure A-3 Accuracy versus Precision5
High accuracy,
high precision
Low accuracy,
high precision
High accuracy,
low precision
Low accuracy,
low precision
Single-point vs. Relative Positioning
In single-point positioning, coordinates of a GPS receiver at an unknown location are sought with respect to the
earth’s reference frame by using the known positions of GPS satellites being tracked. The position solution
generated by the receiver is initially developed in earth-centered coordinates which can subsequently be converted
to any other coordinate system. With as few as four GPS satellites in view, the absolute position of the receiver in
three-dimensional space can be determined. Only one receiver is needed. With Selective Availability (SA) active,
the typical horizontal accuracy obtainable using single-point positioning is of the order of 100 m (95% of the time).
In relative positioning, also known as differential positioning, the coordinates of a GPS receiver at an unknown
point (the “remote” station) are sought with respect to a GPS receiver at a known point (the “reference” station).
The concept is illustrated in Figure A-4. The relative-position accuracy of two receivers locked on the same
satellites and not far removed from each other - up to tens of kilometers - is extremely high. The largest error
contributors in single-point positioning are those associated with SA and atmospheric-induced effects. These
errors, however, are highly correlated for adjacent receivers and hence cancel out in relative measurements. Since
the position of the reference station can be determined to a high degree of accuracy using conventional surveying
techniques, any differences between its known position and the position computed using GPS techniques can be
attributed to various components of error as well as the receiver’s clock bias. Once the estimated clock bias is
removed, the remaining error on each pseudorange can be determined. The reference station sends information
about each satellite to the remote station, which in turn can determine its position much more exactly than would
be possible otherwise.
The advantage of relative positioning is that much greater precision (presently as low as 2 mm, depending on the
method and environment) can be achieved than by single-point positioning. In order for the observations of the
reference station to be integrated with those of the remote station, relative positioning requires either a data link
between the two stations (if the positioning is to be achieved in real-time) or else post-processing of the data
collected by the remote station. At least four GPS satellites in view are still required. The absolute accuracy of the
remote station’s computed position will depend on the accuracy of the reference station’s position.
5. Environment Canada, 1993, Guideline for the Application of GPS Positioning, p. 22.
Minister of Supply and Services Canada
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GPS Overview
Figure A-4 Example of Differential Positioning
GPS satellites
GPS antenna
Differential
data
GPS antenna
(shown with
choke-ring ground plane)
Radio
RX
GPS
RX
User with hand-held
computer
Radio
TX
GPS
RX
Remote station
Reference station
Static vs. Kinematic Positioning
Static and kinematic positioning refer to whether a GPS receiver is stationary or in motion while collecting GPS
data.
Real-time vs. Post-mission Data Processing
Real-time or post-mission data processing refer to whether the GPS data collected by the receiver is processed as
it is received or after the entire data-collection session is complete.
A.3.1 DIFFERENTIAL POSITIONING
There are two types of differential positioning algorithms: pseudorange and carrier phase. In both of these
approaches, the “quality” of the positioning solution generally increases with the number of satellites which can be
simultaneously viewed by both the reference and remote station receivers. As well, the quality of the positioning
solution increases if the distribution of satellites in the sky is favorable; this distribution is quantified by a figure
of merit, the Position Dilution of Precision (PDOP), which is defined in such a way that the lower the PDOP, the
better the solution.
Due to the many different applications for differential positioning systems, two types of position solutions are
possible. NovAtel’s carrier-phase algorithms can generate both matched and low-latency position solutions, while
NovAtel’s pseudorange algorithms generate only low-latency solutions. These are described below:
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GPS Overview
1.
The matched position solution is computed at the remote station when the observation information for
a given epoch has arrived from the reference station via the data link. Matched observation set pairs are
observations by both the reference and remote stations which are matched by time epoch, and contain
the same satellites. The matched position solution is the most accurate one available to the operator of
the remote station, but it has an inherent latency – the sum of time delays between the moment that the
reference station makes an observation and the moment that the differential information is processed at
the remote station. This latency depends on the computing speed of the reference station receiver, the
rates at which data is transmitted through the various links, and the computing speed of the remote sta-
tion; the overall delay is of the order of one second. Furthermore, this position cannot be computed any
more often than the observations are sent from the reference station. Typically, the update rate is one
solution every two seconds.
2.
The low latency (or extrapolated) position solution is based on a prediction. Instead of waiting for the
observations to arrive from the reference station, a model (based on previous reference station observa-
tions) is used to estimate what the observations will be at a given time epoch. These estimated reference
station observations are combined with actual measurements taken at the remote station to provide the
position solution. Because only the reference station observations are predicted, the remote station’s dy-
namics will be accurately reflected. The latency in this case (the time delay between the moment that a
measurement is made by the remote station and the moment that a position is made available) is deter-
mined only by the remote processor’s computational capacity; the overall delay is of the order of 100
ms. Low-latency position solutions can be computed more often than matched position solutions; the
update rate can reach 4 solutions per second. The low-latency positions will be provided for data gaps
between matched positions of up to 30 seconds (for a carrier-phase solution) or 60 seconds (for a pseu-
dorange solution, unless adjusted using the DGPSTIMEOUT command). A general guideline for the
additional error incurred due to the extrapolation process is shown in Table 1-2.
A.3.2 PSEUDORANGE ALGORITHMS
Pseudorange algorithms correlate the pseudorandom code on the GPS signal received from a particular satellite,
with a version generated within the reference station receiver itself. The time delay between the two versions,
multiplied by the speed of light, yields the pseudorange (so called because it contains several errors) between the
reference station and that particular satellite. The availability of four pseudoranges allows the reference station
receiver to compute its position (in three dimensions) and the offset required to synchronize its clock with GPS
system time. The discrepancy between the reference station receiver’s computed position and its known position
is due to errors and biases on each pseudorange. The reference station receiver sums these errors and biases for
each pseudorange, and then broadcasts these corrections to the remote station. The remote receiver applies the
corrections to its own measurements; its corrected pseudoranges are then processed in a least-squares algorithm to
obtain a position solution.
The “wide correlator” receiver design that predominates in the GPS industry yields accuracies of 3-5 m (SEP).
NovAtel’s patented Narrow Correlator tracking technology reduces noise and multipath interference errors,
yielding accuracies of 1 m (SEP).
Pseudorange Differential Positioning
GPS SYSTEM ERRORS
In general, GPS SPS C/A code single point pseudorange positioning systems are capable of absolute position
accuracies of about 100 meters or less. This level of accuracy is really only an estimation, and may vary widely
depending on numerous GPS system biases, environmental conditions, as well as the GPS receiver design and
engineering quality.
There are numerous factors which influence the single point position accuracies of any GPS C/A code receiving
system. As the following list will show, a receiver’s performance can vary widely when under the influences of
these combined system and environmental biases.
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•
Ionospheric Group Delays – The earth’s ionospheric layers cause varying degrees of GPS
signal propagation delay. Ionization levels tend to be highest during daylight hours causing
propagation delay errors of up to 30 meters, whereas night time levels are much lower and
may be up to 6 meters.
•
Tropospheric Refraction Delays – The earth’s tropospheric layer causes GPS signal
propagation delays which bias the range measurements. The amount of delay is at the
minimum (about three metres) for satellite signals arriving from 90 degrees above the
horizon (overhead), and progressively increases as the angle above the horizon is reduced to
zero where delay errors may be as much as 50 metres at the horizon.
•
•
•
Ephemeris Errors – Some degree of error always exists between the broadcast ephemeris’
predicted satellite position and the actual orbit position of the satellites. These errors will
directly affect the accuracy of the range measurement.
Satellite Clock Errors – Some degree of error also exists between the actual satellite clock
time and the clock time predicted by the broadcast data. This broadcast time error will cause
some bias to the pseudorange measurements.
Receiver Clock Errors – Receiver clock error is the time difference between GPS receiver
time and true GPS time. All GPS receivers have differing clock offsets from GPS time that
vary from receiver to receiver by an unknown amount depending on the oscillator type and
quality (TCXO vs. OCXO, etc.). However, because a receiver makes all of its single point
pseudorange measurements using the same common clock oscillator, all measurements will
be equally offset, and this offset can generally be modeled or quite accurately estimated to
effectively cancel the receiver clock offset bias. Thus, in single point positioning, receiver
clock offset is not a significant problem. However, in pseudorange differential operation,
between-receiver clock offset is a source of uncorrelated bias.
•
•
Selective Availability (SA) – Selective availability is when the GPS Control Segment
intentionally corrupts satellite clock timing and broadcast orbit data to cause reduced
positioning accuracy for general purpose GPS SPS users (non-military). When SA is active,
range measurements may be biased by as much as 30 metres.
Multipath Signal Reception – Multipath signal reception can potentially cause large
pseudorange and carrier phase measurement biases. Multipath conditions are very much a
function of specific antenna site location versus local geography and man-made structural
influences. Severe multipath conditions could skew range measurements by as much as 100
information.
The NovAtel GPSCard receivers are capable of absolute single point positioning accuracies of 15 meters CEP
(GDOP < 2; no multipath) when SA is off and 40 meters CEP while AS is on. (As the status of selective availability
is generally unknown by the real-time GPS user, the positioning accuracy should be considered to be that of when
AS is on).
The general level of accuracy available from single point operation may be suitable for many types of positioning
such as ocean going vessels, general aviation, and recreational vessels that do not require position accuracies of
better than 100 meters CEP. However, increasingly more and more applications desire and require a much higher
degree of accuracy and position confidence than is possible with single point pseudorange positioning. This is
where differential GPS (DGPS) plays a dominant role in higher accuracy real-time positioning systems.
SINGLE POINT AVERAGING WITH THE GPSCARD
By averaging many GPS measurement epochs over several hours, it is possible to achieve an absolute position
based on the WGS 84 datum to better than five meters. This section attempts to explain how the position averaging
function operates and to provide an indication of the level of accuracy that can be expected versus total averaging
time.
The POSAVE command implements position averaging for reference stations. Position averaging will continue for
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a specified number of hours or until the averaged position is within specified accuracy limits. Averaging will stop
when the time limit or the horizontal standard deviation limit or the vertical standard deviation limit is achieved.
When averaging is complete, the FIX POSITION command will automatically be invoked.
If the maximum time is set to 1 hour or larger, positions will be averaged every 10 minutes and the standard
deviations reported in the PAVA/B log should be correct. If the maximum time is set to less than 1 hour, positions
will be averaged once per minute and the standard deviations reported in the log will likely not be accurate; also,
the optional horizontal and vertical standard deviation limits cannot be used.
If the maximum time that positions are to be measured is set to 24, for example, you can then log PAVA with the
trigger ‘onchanged’ to see the averaging status. i.e.,
posave 24
log com1 pava onchanged
You could initiate differential logging, then issue the POSAVE command followed by the SAVECONFIG command.
This will cause the GPSCard to average positions after every power-on or reset, then invoke the FIX POSITION
command to enable it to send differential corrections.
The position accuracy that may be achieved by these methods will be dependent on many factors: average satellite
geometry, sky visibility at antenna location, satellite health, time of day, etc. The following graph summarizes the
results of several examples of position averaging over different time periods. The intent is to provide an idea of the
relationship between averaging time and position accuracy. All experiments were performed using a single
frequency receiver with an ideal antenna location, see Figure A-5.
Figure A-5 Single Point Averaging
NOTE: This graph represents typical results using position averaging.
35
30
25
20
15
10
5
0
0
4
8
12
16
20
24
28
32
36
40
44
48
Time (hours)
Latitude
Longtitude
Height
This function is useful for obtaining the WGS84 position of a point to a reasonable accuracy without having to
implement differential GPS. It is interesting to note that even a six hour occupation can improve single point GPS
accuracy from over fifty meters to better than five meters. This improved accuracy is primarily due to the
reductions of the multipath and selective availability errors in the GPS signal.
Again, it is necessary to keep in mind that the resulting standard deviations of the position averaging can vary quite
a bit, especially over relatively short averaging times. To illustrate, the position averaging function was run for a
period of one hour at three different times during the day. The resulting standard deviation in latitude varied from
4.7 to 7.0 meters. Similarly, the variation in longitude and height were 4.9 to 6.7 meters and 10.9 to 12.5 meters
respectively. This degree of variation is common for averaging periods of less than 12 hours due to changes in the
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GPS Overview
satellite constellation. The graph, however, should at least provide some indication of the accuracy one may expect
from single point position averaging.
Dual Station Differential Positioning
It is the objective of operating in differential mode to either eliminate or greatly reduce most of the errors
introduced by the above types of system biases. Pseudorange differential positioning is quite effective in largely
removing most of the biases caused by satellite clock error, ionospheric and tropospheric delays (for baselines less
than 50 km), ephemeris prediction errors, and SA. However, the biases caused by multipath reception and receiver
clock offset are uncorrelated between receivers and thus cannot be cancelled by "between receiver single
differencing" operation.
Differential operation requires that stations operate in pairs. Each pair consists of a reference station (or control
station) and a remote station. A differential network could also be established when there is more than one remote
station linked to a single reference station.
In order for the differential pair to be effective, differential positioning requires that both reference and remote
station receivers track and collect satellite data simultaneously from common satellites. When the two stations are
in relatively close proximity (< 50 km), the pseudorange bias errors are considered to be nearly the same and can
be effectively cancelled by the differential corrections. However, if the baseline becomes excessively long, the
bias errors begin to decorrelate, thus reducing the accuracy or effectiveness of the differential corrections.
Figure A-6 Typical Differential Configuration
Radio Data Link
GPSAntenna
With Chokering
Differential
Corrections
Input
Modem
Differential
Corrections
Output
GPS Receiver
Reference Station
Remote Station
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THE REFERENCE STATION
The nucleus of the differential network is the reference station. To function as a base station, the GPS receiver
antenna must be positioned at a control point whose position is precisely known in the GPS reference frame.
Typically, the fixed position will be that of a geodetic marker or a pre-surveyed point of known accuracy.
The reference receiver must then be initialized to fix its position to agree with the latitude, longitude, and height
of the phase centre of the reference station GPS receiver antenna. Of course, the antenna offset position from the
marker must be accurately accounted for.
Because the reference station’s position is fixed at a known location, it can now compute the range of its known
position to the satellite. The reference station now has two range measurements with which to work: computed
pseudoranges based on its known position relative to the satellite, and measured pseudoranges which assumes the
receiver position is unknown. Now, the reference station’s measured pseudorange (unknown position) is
differenced against the computed range (based on known position) to derive the differential correction which
represents the difference between known and unknown solutions for the same antenna. This difference between the
two ranges represents the combined pseudorange measurement errors resulting from receiver clock errors,
atmospheric delays, satellite clock error, orbital errors, and SA.
The reference station will derive pseudorange corrections for each satellite being tracked. These corrections can
now be transmitted over a data link to one or more remote stations. It is important to ensure that the reference
station’s FIX POSITION setting be as accurate as possible, as any errors here will directly bias the pseudorange
corrections computed, and can cause unpredictable results depending on the application and the size of the base
station position errors. As well, the reference station’s pseudorange measurements may be biased by multipath
reception.
THE REMOTE STATION
A remote station is generally any receiver whose position is of unknown accuracy, but has ties to a reference station
through an established data link. If the remote station is not receiving differential corrections from the reference
station, it is essentially utilizing single point positioning measurements for its position solutions, thus is subject to
the various GPS system biases. However, when the remote GPS receiver is receiving a pseudorange correction from
the reference station, this correction is algebraically summed against the local receiver’s measured pseudorange,
thus effectively cancelling the effects of orbital and atmospheric errors (assuming baselines < 50 km), as well as
eliminating satellite clock error.
The remote must be tracking the same satellites as the reference in order for the corrections to take effect. Thus,
only common satellites will utilize the differential corrections. When the remote is able to compute its positions
based on pseudorange corrections from the reference station, its position accuracies will approach that of the
reference station. Remember, the computed position solutions are always that of the GPS receiving antenna phase
centre.
A.4 CARRIER-PHASE ALGORITHMS
Carrier-phase algorithms monitor the actual carrier wave itself. These algorithms are the ones used in real-time
kinematic (RTK) positioning solutions - differential systems in which the remote station, possibly in motion,
requires reference-station observation data in real-time. Compared to pseudorange algorithms, much more
accurate position solutions can be achieved: carrier-based algorithms can achieve accuracies of 1-2 cm (CEP).
A carrier-phase measurement is also referred to as an accumulated delta range (ADR). At the L1 frequency, the
wavelength is 19 cm; at L2, it is 24 cm. The instantaneous distance between a GPS satellite and a receiver can be
thought of in terms of a number of wavelengths through which the signal has propagated. In general, this number
has a fractional component and an integer component (such as 124 567 967.330 cycles), and can be viewed as a
pseudorange measurement (in cycles) with an initially unknown constant integer offset. Tracking loops can
compute the fractional component and the change in the integer component with relative ease; however, the
determination of the initial integer portion is less straight-forward and, in fact, is termed the ambiguity.
In contrast to pseudorange algorithms where only corrections are broadcast by the reference station, carrier-phase
algorithms typically “double difference” the actual observations of the reference and remote station receivers.
Double-differenced observations are those formed by subtracting measurements between identical satellite pairs
on two receivers:
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ADRdouble difference = (ADRrx A,sat i - ADRrx A,sat j) - (ADRrx B,sat i - ADRrx B,sat j
)
An ambiguity value is estimated for each double-difference observation. One satellite is common to every satellite
pair; it is called the reference satellite, and it is generally the one with the highest elevation. In this way, if there
are n satellites in view by both receivers, then there will be n-1 satellite pairs. The difference between receivers A
and B removes the correlated noise effects, and the difference between the different satellites removes each
receiver’s clock bias from the solution.
In the NovAtel RTK system, a floating (or “continuous-valued”) ambiguity solution is continuously generated
from a Kalman filter. When possible, fixed-integer ambiguity solutions are also computed because they are more
accurate, and produce more robust standard-deviation estimates. Each possible discrete ambiguity value for an
observation defines one lane; that is, each lane corresponds to a possible pseudorange value. There are a large
number of possible lane combinations, and a receiver has to analyze each possibility in order to select the correct
one. For single-frequency receivers, there is no alternative to this brute-force approach. However, one advantage
of being able to make both L1 and L2 measurements is that linear combinations of the measurements made at both
frequencies lead to additional values with either “wider” or “narrower” lanes. Fewer and wider lanes make it easier
for the software to choose the correct lane, having used the floating solution for initialization. Once the correct
wide lane has been selected, the software searches for the correct narrow lane. Thus, the searching process can
more rapidly and accurately home in on the correct lane when dual-frequency measurements are available.
Changes in the geometry of the satellites aids in ambiguity resolution; this is especially noticeable in L1-only
solutions. In summary, NovAtel’s RTK system permits L1/L2 receivers to choose integer lanes while forcing L1-
only receivers to rely exclusively on the floating ambiguity solution.
Once the ambiguities are known, it is possible to solve for the vector from the reference station to the remote
station. This baseline vector, when added to the position of the reference station, yields the position of the remote
station.
In the NovAtel RTK system, the floating ambiguity and the integer position solutions (when both are available) are
continuously compared for integrity purposes. The better one is chosen and output in the receiver’s matched-
position logs. The “best” ambiguities determined are used with the remote station’s local observations and a
reference station observation model to generate the remote station’s low-latency observations.
NovAtel’s RTK product line consists of RT-2 and RT-20 software. Performance characteristics of each are
described in Appendix E.
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Multipath Elimination Technology
B Multipath Elimination Technology
B
MULTIPATH ELIMINATION TECHNOLOGY
Multipath signal reception is one of the most plaguing problems that detracts from the accuracy potential of GPS
pseudorange differential positioning systems. This section will provide a brief look at the problems of multipath
reception and some solutions developed by NovAtel.
B.1 MULTIPATH
Multipath occurs when an RF signal arrives at the receiving antenna from more than one propagation route
(multiple propagation paths).
Figure B-1 Illustration of GPS Signal Multipath
Why Does Multipath Occur?
When the GPS signal is emitted from the satellite antenna, the RF signal propagates away from the antenna in many
directions. Because the RF signal is emitted in many directions simultaneously and is traveling different paths,
these signals encounter various and differing natural and man-made objects along the various propagation routes.
Whenever a change in medium is encountered, the signal is either absorbed, attenuated, refracted, or reflected.
Refraction and reflection cause the signals to change direction of propagation. This change in path directions often
results in a convergence of the direct path signal with one or more of the reflected signals. When the receiving
antenna is the point of convergence for these multipath signals, the consequences are generally not favorable.
Whenever the signal is refracted, some signal polarity shifting takes place; and when full reflection occurs, full
polarity reversal results in the propagating wave. The consequences of signal polarity shifting and reversal at the
receiving antenna vary from minor to significant. As well, refracted and reflected signals generally sustain some
degree of signal amplitude attenuation.
It is generally understood that, in multipath conditions, both the direct and reflected signals are present at the
antenna and the multipath signals are lower in amplitude than the direct signal. However, in some situations, the
direct signal may be obstructed or greatly attenuated to a level well below that of the received multipath signal.
Obstruction of direct path signals is very common in city environments where many tall buildings block the line
of sight to the satellites. As buildings generally contain an abundance of metallic materials, GPS signal reflections
are abundant (if not overwhelming) in these settings. Obstructions of direct path signals can occur in wilderness
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Multipath Elimination Technology
settings as well. If the GPS receiver is in a valley with nearby hills, mountains and heavy vegetation, signal
obstruction and attenuation are also very common.
Consequences of Multipath Reception
Because GPS is a radio ranging and positioning system, it is imperative that ground station signal reception from
each satellite be of direct line of sight. This is critical to the accuracy of the ranging measurements. Obviously,
anything other than direct line of sight reception will skew and bias the range measurements and thus the
positioning triangulation (or more correctly, trilateration). Unfortunately, multipath is almost always present to
some degree, due to real world conditions.
When a GPS multipath signal converges at the GPS antenna, there are two primary problems that occur:
1. a multiple signal with amplitude and phase shifting, and
2. a multiple signal with differing ranges.
When a direct signal and multipath signal are intercepted by the GPS antenna, the two signals will sum according
to the phase and amplitude of each. This summation of signals causes the composite to vary greatly in amplitude,
depending on the degree of phase shift between the direct signal versus the multipath signal. If the multipath signal
lags the direct path signal by less than 90° the composite signal will increase in amplitude (relative to the direct
signal, depending on the degree of phase shift between 0° and 90°). As well, if the multipath signal lags the direct
path signal by greater than 90° but less than 270° the composite signal will decrease in amplitude. Depending on
the relative amplitude of the multipath signal (or signals), the composite signal being processed by the receiver
correlator may experience substantial amplitude variations, which can play havoc with the receiver’s automatic
gain control circuitry (AGC) as it struggles to maintain constant signal levels for the receiver correlator. A worst
case scenario is when the multipath signal experiences a lag of 180° and is near the same strength as the direct path
signal – this will cause the multipath signal to almost completely cancel out the direct path signal, resulting in loss
of satellite phase lock or even code lock.
Because a multipath signal travels a greater distance to arrive at the GPS antenna, the two C/A code correlations are,
by varying degrees, displaced in time, which in turn causes distortion in the correlation peak and thus ambiguity
errors in the pseudorange (and carrier phase, if applicable) measurements.
As mentioned in previous paragraphs, it is possible that the received multipath signal has greater amplitude than
the direct path signal. In such a situation the multipath signal becomes the dominant signal and receiver
pseudorange errors become significant due to dominant multipath biases and may exceed 150 meters. For single
point pseudorange positioning, these occasional levels of error may be tolerable, as the accuracy expectations are
at the 40 meter CEP level (using standard correlator). However, for pseudorange single differencing DGPS users,
the accuracy expectations are at the one to five mere CEP level (with no multipath). Obviously, multipath biases
now become a major consideration in trying to achieve the best possible pseudorange measurements and position
accuracy.
If a differential reference station is subject to significant multipath conditions, this in turn will bias the range
corrections transmitted to the differential remote receiver. And in turn, if the remote receiver also experiences a
high level of multipath, the remote receiver position solutions will be significantly biased by multipath from both
stations. Thus, when the best possible position solutions are required, multipath is certainly a phenomenon that
requires serious consideration.
B.2 HARDWARE SOLUTIONS FOR MULTIPATH REDUCTION
A few options exist by which GPS users may reduce the level of multipath reception. Among these include: antenna
site selection, special antenna design, and ground plane options.
Antenna Site Selection
Multipath reception is basically a condition caused by environmental circumstances. Some of these conditions you
may have a choice about and some you may not.
Many GPS reception problems can be reduced, to some degree, by careful antenna site selection. Of primary
importance is to place the antenna so that unobstructed line-of-sight reception is possible from horizon to horizon
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Multipath Elimination Technology
and at all bearings and elevation angles from the antenna. This is, of course, the ideal situation, which may not be
possible under actual operating conditions.
Try to place the antenna as far as possible from obvious reflective objects, especially reflective objects that are
above the antenna’s radiation pattern horizon. Another solution would be to install an RF fence pointing toward
the reflector which is causing the multipath. When installed close to the antenna, it effectively attenuates the
unwanted multipath signal. Close-in reflections will be stronger, and typically have a shorter propagation delay
allowing for autocorrelation of signals with a propagation delay of less than one C/A code chip (300 meters).
Figure B-2 Illustration of GPS Signal Multipath vs. Increased Antenna Height
When the antenna is in an environment with obstructions and reflective surfaces in the vicinity, it is advantageous
to mount the antenna as high as possible to reduce the obstructions, as well as reception from reflective surfaces,
as much as possible.
Water bodies are extremely good reflectors of GPS signals. Because of the short wavelengths at GPS frequencies,
even small ponds and water puddles can be a strong source of multipath reception, especially for low angle
satellites. Thus, it can be concluded that water bodies such as lakes and oceans are among the most troublesome
multipath environments for low angle signal reception. Obviously, water body reflections are a constant problem
for ocean going vessels.
Antenna Designs
Low angle reflections, such as from water bodies, can be reduced by careful selection of antenna design. For
example, flat plate microstrip patch antennas have relatively poor reception properties at low elevation angles near
their radiation pattern horizon.
Quadrifilar helix antennas and other similar vertically high profile antennas tend to have high radiation gain
patterns at the horizon. These antennas, in general, are more susceptible to the problems resulting from low angle
multipath reception. So, for marine vessels, this type of antenna encourages multipath reception. However, the
advantages of good low angle reception also means that satellites can be acquired more easily while rising in the
horizon. As well, vessels subject to pitch and roll conditions will experience fewer occurrences of satellite loss of
lock.
A good antenna design will also incorporate some form of left hand circular polarization (LHCP) rejection.
Multipath signals change polarization during the refraction and reflection process. This means that generally,
multipath signals may be LHCP oriented. This property can be used to advantage by GPS antenna designers. If a
GPS antenna is well designed for RHCP polarization, then LHCP multipath signals will automatically be attenuated
somewhat during the induction into the antenna. To further enhance performance, antennas can be designed to
increase the rejection of LHCP signals. NovAtel’s GPSAntenna model 501 is an example of an antenna optimized
to further reject LHCP signals by more than 10 dB.
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Figure B-3 Illustration of Quadrifilar vs. Microstrip Patch Antennae
Quadrifilar Elements
Radome
Antenna Patch
Dielectric
Patch Ground Plane
Quadrifilar Helix Antenna
Microstrip Patch Antenna
Antenna Ground Planes
Nearby objects can influence the radiation pattern of an antenna. Thus, one of the roles of the antenna ground plane
is to create a stabilizing artificial environment on which the antenna rests and which becomes a part of the antenna
structure and its resultant radiation pattern.
A small ground plane (relative to one wavelength at the operating frequency) may have minimal stabilizing effect,
whereas a large ground plane (multiple wavelengths in size) will have a highly stabilizing effect.
Large ground planes also exhibit a shielding effect against RF signal reflections originating below the antenna’s
radiation pattern horizon. This can be a very effective low angle shield when the antenna is elevated on a hill or
other structure above other reflecting surfaces such as vehicles, railway tracks, soil with high moisture content,
water bodies, etc.
One of the drawbacks of a "flat plate" ground plane is that it gives a “hard boundary condition”, ie. allowing
electromagnetic waves to propagate along the ground plane and diffract strongly from its edge. The “soft
boundary” condition, on the other hand, will prevent the wave from propagating along the surface of the ground
plane and thereby reducing the edge diffraction effects. As a result the antenna will exhibit a completely different
radiation pattern. The “soft boundary” condition is typically achieved by a quarter wavelength deep, transversely
corrugated ground plane surface (denoted as “choke ring ground plane”). When the depth of the corrugation (choke
rings) is equal to a quarter wavelength, the surface wave vanishes, and the surface impedance becomes infinite and
hence provides the “soft boundary” condition for the electromagnetic field. This results in modifications to the
antenna radiation pattern that is characterized by low back lobe levels, no ripples in the main lobe, sharper
amplitude, roll-off near the horizon and better phase center stability (there are smaller variations in 2 axes). This is
what makes NovAtel's GPS antennas so successful when used with the NovAtel GPSAntenna choke ring ground
plane.
NovAtel’s Internal Receiver Solutions for Multipath Reduction
The multipath antenna hardware solutions described in the previous paragraphs are capable of achieving varying
degrees of multipath reception reduction. These options, however, require specific conscious efforts on the part of
the GPS user. In many situations, especially kinematic, few (if any) of the above solutions may be effective or even
possible to incorporate. By far, the best solutions are those which require little or no special efforts in the field on
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Multipath Elimination Technology
the part of the GPS user. This is what makes NovAtel’s internal receiver solutions so desirable and practical.
NovAtel has placed long term concerted effort into the development of internal receiver solutions and techniques
that achieve multipath reduction, all of which are transparent to the GPSCard user. These achievements have led
to Narrow Correlator tracking technology.
It utilizes innovative patented correlator delay lock loop (DLL) techniques. As it is beyond the scope of this manual
to describe in detail how the correlator techniques achieve the various levels of performance, the following
paragraphs will provide highlights of the advantages of this technology.
NARROW CORRELATOR TRACKING TECHNOLOGY
NovAtel’s MiLLennium GPSCard receivers achieve a higher level of pseudorange positioning "performance" vs.
standard (wide) correlator, by virtue of its celebrated Narrow Correlator tracking technology. By utilizing Narrow
Correlator tracking techniques, the MiLLennium GPSCard is capable of pseudorange measurement improvements
better than 2:1 when compared to standard correlation techniques. As well, the Narrow Correlator tracking
technology inherently reduces multipath reception (approaching a factor of eight compared to standard correlator)
by virtue of its narrower autocorrelation function.
Figure B-4, Page 78 illustrates relative multipath-induced tracking errors encountered by standard correlators vs.
NovAtel’s Narrow Correlator tracking technology. As can be seen, standard correlators are susceptible to
substantial multipath biases for C/A code chip delays of up to 1.5 chip, with the most significant C/A code multipath
bias errors occurring at about 0.25 and 0.75 chip (approaching 80 m error). On the other hand, the Narrow
Correlator tracking technology multipath susceptibility peaks at about 0.2 chip (about 10 m error) and remains
relatively constant out to 0.95 chip, where it rapidly declines to negligible errors after 1.1 chip.
While positioning in single point mode, the multipath and ranging improvement benefits of a Narrow Correlator
tracking technology receiver vs. standard correlator are overridden by a multitude of GPS system biases and errors
(with or without an antenna choke ring ground plane). In either case, positioning accuracy will be in the order of
40 meters CEP (SA on, no multipath). However, the benefits of the Narrow Correlator tracking technology become
most significant during pseudorange DGPS operation, where the GPS systematic biases are largely cancelled.
Receivers operating DGPS with standard correlator technology typically achieve positioning accuracies in the two
to five meter CEP range (low multipath environment and using choke ring ground plane), while NovAtel’s Narrow
Correlator tracking technology receivers are able to achieve positioning accuracies in the order of 0.75 meter CEP
(low multipath environment and using choke ring ground plane). The Narrow Correlator tracking technology
achieves this higher accuracy through a combination of lower noise ranging measurements combined with its
improved multipath resistance when compared to the standard correlator.
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Figure B-4 Comparison of Multipath Envelopes
SUMMARY
Any localized propagation delays or multipath signal reception cause biases to the GPS ranging measurements that
cannot be differenced by traditional DGPS single or double differencing techniques. Generally speaking, single
point positioning systems are not too concerned with multipath reception, as the system errors are quite large to
begin with. However, multipath is recognized as the greatest source of errors encountered by a system operating
in differential mode. It has been discussed that careful site selection and good antenna design combined with a
choke ring ground plane are fairly effective means of reducing multipath reception.
Internal receiver solutions for multipath elimination are achieved through various types of correlation techniques,
where the "standard correlator" is the reference by which all other techniques can be compared.
The Narrow Correlator tracking technology has a two fold advantage over standard correlators: improved ranging
measurements due to a sharper, less noisy correlation peak, and reduced susceptibility to multipath due to rejection
of C/A code delays of greater than 1.0 chip. When used with a choke ring ground plane, the Narrow Correlator
tracking technology provides substantial performance gains over standard correlator receivers operating in
differential mode.
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C
Commands Summary
C
COMMANDS SUMMARY
C
COMMANDS SUMMARY
ACCEPT
The ACCEPT command controls the processing of input data and is primarily used to set the GPSCard’s COM port
command interpreter for acceptance of various data formats. Each port can be controlled to allow ASCII command
processing (default), binary differential data processing, or the command interpreter can be turned off.
The command interpreter automatically distinguishes between ASCII commands and certain NovAtel-format
ASCII and binary logs without receiving an ACCEPT command.
MiLLennium GPSCards will by default interpret $RTCM59A corrections, and will interpret RTCM59 if ACCEPT
RTCM has been entered.
On certain GPSCards the ACCEPT port COMMANDS mode will by default accept, interpret, and process these
data messages: $PVAA, PVAB, $REPA, REPB, $RTCM1A, $RTCAA, $RTCM3A, $RTCM9A, $RTCM16A,
$TM1A and TM1B, without any other initialization required.
The command interpreter can process some NovAtel-format binary logs (which have a proprietary header) or
ASCII logs without receiving an ACCEPT command. Therefore, the ACCEPT command is needed only for the
RTCA, RTCM and CMR logs. When using ACCEPT RTCM, the interpretation of the RTCM data will follow the
rules defined by the RTCMRULE command (see Chapter 4, Message Formats, Page 45). In the default processing
mode (ACCEPT port COMMANDS), input ASCII data received by the specified port will be interpreted and
processed as a valid GPSCard command. If the input data cannot be interpreted as a valid GPSCard command, an
error message will be echoed from that port (if the command MESSAGES is “ON”). When valid data is accepted
and interpreted by the port, it will be processed and acknowledged by echoing the port prompt (with the exception
of VERSION and HELP commands, which reply with data before the prompt).
In the binary differential data processing modes, (ACCEPT port RTCA/RTCM/CMR), only the applicable data
types specified will be interpreted and processed by the specified COM port; no other data will be interpreted. It
is important to note that only one out of two COM ports can be specified to accept binary differential correction
data. Both ports cannot be set to accept differential data at the same time.
When ACCEPT port NONE is set, the specified port will be disabled from interpreting any input data. Therefore,
no commands or differential corrections will be decoded by the specified port. However, data can still be logged
out from the port, and data can be input to the port for formatting into Pass-Through logs (see Chapter 5, Page
45). If the GPSCard operator wants to time-tag non-GPS messages as a Pass-Through log, it is recommended that
the port accepting the Pass-Through data be set to “NONE”. This will prevent the accepting GPSCard COM port
from echoing error messages in response to receipt of unrecognized data. If you do not wish to disable the
command interpreter, and do want to disable message error reporting, see the MESSAGES command, Appendix C,
The GPSCard user can monitor the differential data link as well as the data decoding process by utilizing the
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Commands Summary
Syntax:
ACCEPT port
option
Syntax
Range Value
Description
Default
ACCEPT
port
-
Command
COM1 or COM2
NONE
Specifies the COM port to be controlled
Turn off Command Interpreter
option
commands
(GPSCard
model
dependent)
COMMANDS
Command Interpreter attempts to interpret all incoming data. Will also interpret certain
ASCII and NovAtel format binary logs.
Interprets RTCAB or raw binary RTCA data only (Types 1,7)
Interprets raw binary RTCM data only (Types 1,2,3,9,16,18,19 and 59N)
Receives CMR messages
RTCA
RTCM
CMR
Example:
accept com1 rtcm
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Commands Summary
ANTENNAPOWER
On MiLLennium GPSCards this command enables or disables the supply of electrical power from the internal
power source of the card to the low-noise amplifier (LNA) of an active antenna. Jumper P301 allows the user to
power the LNA either by an internal power source (plug connects pins 1&2) or an optional external power source
(plug connects pins 2&3); or, the user can cut off all power to the antenna (plug removed). For more information
on these jumper settings, please refer to Chapter 3 of the MiLLennium Guide to Installation and Operation. The
ANTENNAPOWER command, which is only relevant when Jumper P301 is set to connect pins 1&2, determines
whether or not internal power is applied to pin 1 of Jumper P301. Table C-1 summarizes the combinations:
Table C-1 Antenna LNA Power Configuration
P301: plug connects
pins 1&2
P301: plug connects
pins 2&3
P301: no plug
no external effect
internal power connected
to LNA
no external effect
ANTENNAPOWER = ON
ANTENNAPOWER = OFF
internal power cut off from no external effect
LNA
no external effect
The setting of this command will affect the way the MiLLennium’s self-test diagnostics (see Table D-5, Page 196)
report the antenna’s status.
Syntax:
ANTENNAPOWER
flag
Command
ANTENNAPOWER
flag
Range Value
Description
Default
Command
on
(none)
ON
Displays status of the internal antenna-power supply.
If plug on P301 joins pins 1&2, connects internal power to the LNA. Antenna status
will be reported as “GOOD” unless a fault is detected, in which case the status will
change to “BAD” and the internal power cut off from pin 1.
OFF
If plug on P301 joins pins1&2, cuts off internal power from theLNA. Antenna status
will always be reported as “GOOD”.
Example:
antennapower off
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Commands Summary
ASSIGN
This command may be used to aid in the initial acquisition of a satellite by allowing you to override the automatic
satellite/channel assignment and reacquisition processes with manual instructions. The command specifies that the
indicated tracking channel search for a specified satellite at a specified Doppler frequency within a specified
Doppler window. The instruction will remain in effect for the specified channel and PRN, even if the assigned
satellite subsequently sets. If the satellite Doppler offset of the assigned channel exceeds that specified by the
Search-Window parameter of the ASSIGN command, the satellite may never be acquired or re-acquired. To cancel
the effects of ASSIGN, you must issue the UNASSIGN or UNASSIGNALL command, or reboot the GPSCard.
When using this command, NovAtel recommends that you monitor the channel tracking status (ETSA/B) of the
assigned channel and then use the UNASSIGN or UNASSIGNALL commands to cancel the command once the channel
has reached channel state 4, the Phase Lock Loop (PLL) state. See Appendix D, Page 155, the ETSA/B ASCII log
NOTE: Assigning a PRN to a channel does not remove the PRN from the search space of the automatic
searcher; only the channel is removed. By default, the automatic searcher only searches for the GPS
satellites (PRNs 1-32).
There are two syntactical forms of this command, as shown below.
Syntax #1:
ASSIGN channel prn
Syntax Range Value
ASSIGN
doppler search-window
Description
Default
Example
assign
0
-
Command
unassignall
channel
0 - 11
Desired channel number from 0 to 11 inclusive (channel 0
represents first channel, channel 11 represents twelfth
channel)
prn
1 - 32
A satellite PRN integer number from 1 to 32 inclusive
Current Doppler offset of the satellite
29
0
doppler
-100,000 to 100,000 Hz
Note:
Satellite motion, receiver antenna motion and
receiver clock frequency error must be included in the
calculation for Doppler frequency.
search-window 0 - 10,000
Error or uncertainty in the Doppler estimate above in Hz
2000
Note:
Any positive value from 0 to 10000 will be
accepted. Example: 500 implies ± 500 Hz.
Example 1:
assign 0,29,0,2000
In example 1, the first channel will try to acquire satellite PRN 29 in a range from -2000 Hz to 2000 Hz until the
satellite signal has been detected.
Example 2:
assign 11,28,-250,0
The twelfth channel will try to acquire satellite PRN 28 at -250 Hz only.
Syntax #2:
ASSIGN
channel
keyword
Syntax
ASSIGN
channel
Range Value
Description
Default
Example
assign
0
-
Command
unassignall
0 - highest channel Desired channel number from maximum channel number
number
inclusive
keyword
IDLE
Idles channel (not case sensitive)
idle
Example 3:
assign 11,idle
In Example 3, Channel 11 will be idled and will not attempt to search for satellites.
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Commands Summary
CLOCKADJUST
All oscillators have some inherent drift. On the MiLLennium GPSCard, the clock and the PPS strobe have a 50 ns
jitter due to the receiver’s attempts to keep the clock as close as possible to GPS time. This option is disabled by
entering CLOCKADJUST DISABLE. The jitter will vanish, but the unsteered and free-running clock will drift
relative to GPS time. CLOCKADJUST must also be disabled if the user wishes to measure the drift rate of the
oscillator using the CLKA/B data logs.
NOTE 1: Please note that, when disabled, the range measurement bias errors will continue to accumulate with
clock drift.
NOTE 2: This feature is to be used by advanced users only.
NOTE 3: Pseudorange, carrier phase and Doppler measurements may jump if CLOCKADJUST DISABLE is
issued while the receiver is tracking.
Syntax:
CLOCKADJUST
switch
Syntax Range Value
Description
Default
CLOCKADJUST
switch
-
Command
Allows or disallows adjustment to the internal clock enable
enable or disable
Example:
clockadjust disable
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Commands Summary
COMn
This command permits you to configure the GPSCard COM port’s asynchronous drivers.
Syntax:
COMn bps
parity databits stopbits handshake echo FIFO
Syntax
Value
Description
Specify COM port
Default
Example
com2
COMn
bps
n = 1 or 2
300, 600, 1200, 2400, 4800, 9600, 19200,
38400, 57600 or 115,200
Specify bit rate
9600
19200
parity
N (none), O (odd) or E (even)
Specify parity
N
E
databits
stopbits
7 or 8
1 or 2
Specify number of data bits
Specify number of stop bits
Specify handshaking
Specify echo
8
7
1
1
handshake N (none), XON (Xon/Xoff) or CTS (CTS/RTS)
N
N
echo
FIFO
ON or OFF
ON or OFF
OFF
ON
OFF
Transmit the First In First Out queue of the ON
GPSCard’s serial port UART.
Examples:
com2 19200,e,7,1,n,on,off
com1 1200,e,8,1,n,on,off
NOTE: Your GPSCard comes configured this way. If you have different parameters you should reconfigure the
communication protocol as per requirements.
COMn_DTR
This command enables versatile control of the DTR handshake line for use with output data logging in conjunction
with external devices such as a radio transmitter. The default state for the COM1 or COM2 DTR line is always high.
Syntax:
COMn_DTR control active [lead] [tail]
Syntax
COMn_DTR
control
Option
n = 1 or 2
high
Description
Selects COM1 or COM2 port
Default
high
Example
com1_dtr
toggle
control is always high
control is always low
low
toggle
control toggles between high and low
(active, lead, and tail fields are TOGGLE options only)
active
high
data available during high
n/a
high
low
data available during low
lead
tail
variable
variable
lead time before data transmission (milliseconds)
tail time after data transmission (milliseconds)
n/a
n/a
300
150
Examples:
com1_dtr toggle,high,300,150
com2_dtr toggle,low,200,110
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Commands Summary
OUTPUT DATA
DTR
Data
150 ms
tail
300 ms
lead
control
COMn_RTS
This command enables versatile control of the RTS handshake line for use with output data logging in conjunction
with external devices such as a radio transmitter. The default state for the COM1 or COM2 RTS line is always high.
COMn_RTS will not influence the COMn command handshake control of incoming commands.
Syntax:
COMn_RTS control active [lead] [tail]
Syntax
COMn_RTS
control
Option
n = 1 or 2
high
Description
Selects COM1 or COM2 port
Default
high
Example
com1_rts
toggle
control is always high
control is always low
low
toggle
control toggles between high and low
(active, lead, and tail fields are TOGGLE options only)
active
high
data available during high
n/a
high
low
data available during low
lead
tail
variable
variable
lead time before data transmission (milliseconds)
tail time after data transmission (milliseconds)
n/a
n/a
200
100
Example:
com1_rts toggle,high,200,100
com2_rts toggle,low,250,125
OUTPUT DATA
Data
100 ms
tail
200 ms
lead
RTS
control
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Commands Summary
CONFIG
This command switches the channel configuration of the GPSCard between pre-defined configurations. When
invoked, this command loads a new satellite channel-configuration and forces the GPSCard to reset. The types of
configurations possible are listed by entering this command:
HELP CONFIG
In some applications, only the standard (default) configuration will be listed in response. The standard
configuration of a MiLLennium GPSCard consists of 12 L1/L2 channel pairs.
Syntax:
CONFIG cfgtype
Command
CONFIG
cfgtype
Option
Description
Default
standard
Command
(none)
configuration name
Displays present channel configuration
Loads new configuration, resets GPSCard
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Commands Summary
CRESET
Configuration Reset. Resets user configuration to the factory default. After a reset, non volatile memory (NVM) is
read for user configuration. This command does not reset the hardware. See the Factory Default Settings .
Syntax:
CRESET
See also the FRESET and RESET commands. These three commands differ in the following way:
RESET
CRESET
FRESET
-
-
-
Resets the hardware. Similar to powering the card off and on again.
Resets user configuration to the factory default. This command does not reset the hardware.
Completely resets the receiver to a factory state. Anything that was saved to NVM is erased
(including Saved Config, Saved Almanac and Channel Config). The hardware is also reset.
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Commands Summary
CSMOOTH
This command sets the amount of carrier smoothing to be performed on the pseudorange measurements carrier.
An input value of 100 corresponds to approximately 100 seconds of smoothing. Upon issuing the command, the
locktime for all tracking satellites is reset to zero. From this point each pseudorange smoothing filter is restarted.
The user must wait for at least the length of smoothing time for the new smoothing constant to take full effect. 20
seconds is the default smoothing constant used in the GPSCard. The optimum setting for this command is
dependent on the user’s application and thus cannot be specified.
Syntax:
CSMOOTH
L1 time
[L2 time]
Syntax
CSMOOTH
L1 time
Range Value
Description
Default
-
Command
2 to 1000
L1 carrier smoothing time constant. 20
Value in seconds
[L2 time]
2 to 1000
L2 carrier smoothing time constant.
Value in seconds
Example:
csmooth 500
NOTE: The CSMOOTH command should only be used by advanced users of GPS.
It may not be suitable for every GPS application. When using CSMOOTH in a differential mode, the same
setting should be used at both the reference and remote station. The shorter the carrier smoothing the
more noise there will be. If you are at all unsure please call NovAtel Customer Service Department, see
Software Support at the start of this manual.
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Commands Summary
DATUM
This command permits you to select the geodetic datum for operation of the receiver. If not set, the value is
defaulted to WGS84. See Table G-2 in Appendix G for a complete listing of all available predefined datums. See
the USERDATUM command for user definable datums. The datum you select will cause all position solutions to be
based on that datum (except PXYA/B which is always based on WGS84).
Syntax:
DATUM option
Syntax
Datum Option
Description
Default
DATUM
any one of 62 predefined
datums
For a complete list of all 62 predefined datums, see Table G-2 in Appendix G. WGS84
USER
User defined datum with parameters specified by the USERDATUM
command (Default WGS84)
Example:
datum tokyo
Sets the system datum to Tokyo
NOTE: The actual datum name must be entered in this command as listed in the NAME column of Table G-2.
Also note that references to datum in the following logs use the GPSCard Datum ID #: MKPA/B, PRTKA/
B, POSA/B and RTKA/B.
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Commands Summary
DGPSTIMEOUT
This command has a two-fold function:
(1)
to set the maximum age of differential data that will be accepted when operating as a remote station. Dif-
ferential data received that is older than the specified time will be ignored. When entering DGPS delay,
you can ignore the ephemeris delay field.
(2)
to set the ephemeris delay when operating as a reference station. The ephemeris delay sets a time value
by which the reference station will continue to use the old ephemeris data. A delay of 120 to 300 seconds
will typically ensure that the remote stations have collected updated ephemeris. After the delay period is
passed, the reference station will begin using new ephemeris data. To enter an ephemeris delay value,
you must first enter a numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference
station, DGPS delay will be ignored.
Syntax:
DGPSTIMEOUT dgps delay ephem delay
Command
DGPSTIMEOUT
dgps delay
Option
Description
Command
Default
min.
2
Maximum age in seconds
60
max.
1000
ephem delay
min.
max.
0
600
Minimum time delay in seconds
120
Example 1 (remote):
dgpstimeout 15
Example 2 (reference):
dgpstimeout 2,300
NOTE 1: The RTCA Standard for SCAT-I stipulates that the maximum age of differential correction messages
cannot be greater than 22 seconds. Therefore, for RTCA logs, the recommended DGPS delay setting is 22.
NOTE 2: The RTCA Standard also stipulates that a reference station shall wait five minutes after receiving a new
ephemeris before transmitting differential corrections. This time interval ensures that the remote
stations will have received the new ephemeris, and will compute differential positioning based upon the
same ephemeris. Therefore, for RTCA logs, the recommended ephemeris delay is 300 seconds.
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Commands Summary
DIFF_PROTOCOL Differential Protocol Control
NOTE: The DIFF_PROTOCOL command should only be used by advanced users of GPS.
Features:
1. A user definable key such that many different types of encoding may be used in the same area without cross
talk between the various “channels”.
2. Encodes all correction data following any header specific to the message type.
3. Non-volatile. When the base station card is restarted, the previously selected encoding key is used for all sub-
sequent differential data.
4. The encoding key is not visible by any method of interrogation.
Syntax:
DIFF_PROTOCOL
DIFF_PROTOCOL
DIFF_PROTOCOL
Type
Key
or
or
DISABLE
Syntax
DIFF_PROTOCOL
type
Range Value
-
Description
Command
Default
1, DISABLE
0 - FFFFFFFF
Encoding Algorithm
32 Bit Encoding key
key
NOTE: If no parameters are given to the command, the encoding type value will be reported. The key value is
not visible at anytime.
The only supported type of encoding is “Type 1”, which will only encode RTCM data with the algorithm described
below.
The non-volatility of the command is acquired via the SAVECONFIG command. This command stores the current
settings in non-volatile memory.
All header information necessary for parsing the incoming data stream remains unencoded.
RTCM/A/B LOGS
The NovAtel log format wrapping of the RTCMA and RTCMB logs remains unencoded and only the raw RTCM
data is encoded beginning after the second word of the message. This will leave the entire header unencoded:
WORD 1
Preamble
Message Type (Frame ID)
Sequence No.
Station ID
Parity
Parity
WORD 2
Modified Z-Count
Encoded data...
Length of Frame
REMAINING...
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Commands Summary
DYNAMICS
This command informs the receiver of user dynamics. It is used to optimally tune receiver parameters.
Syntax:
DYNAMICS user_dynamics
Command
DYNAMICS
Description
receiver is an aircraft
Default
dynamics
air
Command
user_dynamics
air
land
receiver is in a land vehicle with velocity less than
110 km/h (30m/s)
foot
receiver is being carried by a person with velocity less than
11 km/h (3m/s)
Example:
dynamics foot
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Commands Summary
ECUTOFF
This command sets the elevation cut-off angle for usable satellites. The GPSCard will not start tracking a satellite
until it rises above the cutoff angle. If there are six or less satellites being tracked and one drops below this angle,
it will continue to be tracked until the signal is lost. However, if there are more than six satellites being tracked,
any that are below the cutoff angle will be dropped completely.
In either case, satellites below the ECUTOFF angle will be eliminated from the internal position and clock offset
solution computations only.
This command permits a negative cut-off angle; it could be used in these situations:
•
•
the antenna is at a high altitude, and thus can look below the local horizon
satellites are visible below the horizon due to atmospheric refraction
Syntax:
ECUTOFF angle
Syntax
ECUTOFF
angle
Range Value
Description
Default
-
Command
Value in degrees (relative to the horizon).
-90° to +90°
0
Example:
ecutoff 5
NOTE 1: When ECUTOFF is set to zero (0), the receiver will track all SVs in view including some within a few
degrees below the horizon.
NOTE 2: Care must be taken when using ECUTOFF because the information you are tracking from lower elevation
satellite signals are going through more atmosphere, for example ionospheric and tropospheric, and
therefore being degraded.
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Commands Summary
EXTERNALCLOCK
Overview
The EXTERNALCLOCK and EXTERNALCLOCK FREQUENCY commands allows the MiLLennium GPSCard to operate
with an optional external oscillator. The user is able to optimally adjust the clock model parameters of the GPSCard
for various types of external clocks. The three-state clock model on GPSCards having access to this command is
different from that used on the other GPSCards.
NOTE: The EXTERNALCLOCK command will affect the interpretation of the CLKA/B log.
There are three steps involved in using an external oscillator:
1. Follow the procedure outlined in your GPSCard’s installation/operation manual for connecting an
external oscillator to your GPSCard.
2. For the chosen oscillator type, use the EXTERNALCLOCK FREQUENCY command to select the operating
frequency – either 5 MHz or 10 MHz.
3. Using the EXTERNALCLOCK command, select a standard oscillator or define a new one; the effect is to
define h0, h-1, and h-2 in the expression for Sy(f) given below.
Steps #2 and #3 define certain parameters used in the clock model for the external oscillator
Theory
An unsteered oscillator can be approximated by a three-state clock model, with two states representing the range
bias and range bias rate, and a third state assumed to be a Gauss-Markov (GM) process representing the range bias
error generated from satellite clock dither. The third state is included because the Kalman filter assumes an
(unmodeled) white input error. The significant correlated errors produced by SA clock dither are obviously not
white and the Markov process is an attempt to handle this kind of short-term variation.
The internal units of the new clock model’s three states (offset, drift and GM state) are meters, meters per second,
and meters. When scaled to time units for the output log, these become seconds, seconds per second, and seconds,
respectively. Note that the old units of the third clock state (drift rate) were meters per second per second.
The user has control over 3 process noise elements of the linear portion of the clock model. These are the h0, h-1,
and h-2 elements of the power law spectral density model used to describe the frequency noise characteristics of
oscillators:
h–2 h–1
2
------- -------
+ h0 + h1f + h2 f
Sy(f) =
+
2
f
f
where f is the sampling frequency and Sy(f) is the clock’s power spectrum. Typically only h0, h-1, and h-2 affect the
clock’s Allan variance and the clock model’s process noise elements.
Usage
Before using an optional external oscillator, several clock model parameters must be set. There are default settings
for a voltage-controlled temperature-compensated crystal oscillator (VCTCXO), ovenized crystal oscillator
(OCXO), Rubidium and Cesium standard; or, the user may choose to supply customized settings.
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Commands Summary
Syntax:
EXTERNALCLOCK option
Command
Option
Description
Revert to the on-board oscillator
Default
EXTERNALCLOCK
disable
see Table C-2
MiLLennium = VCTCXO
ocxo
Set defaults for ovenized crystal oscillator
Set defaults for rubidium oscillator
Set defaults for cesium oscillator
rubidium
cesium
user h h h
Define custom values for process noise elements
0 -1 -2
Example:
externalclock user 1.0e-20 1.0e-24 1.0e-28
Table C-2 Default Values of Process Noise Elements
h
h
h
-2
Timing Standard
0
-1
VCTCXO
OCXO
1.0 e-21
2.51 e-26
1.0 e-23
2.0 e-20
1.0 e-20
2.51 e-23
1.0 e-22
7.0 e-23
2.0 e-20
2.51 e-22
1.3 e-26
4.0 e-29
rubidium
cesium
user (min / max)
1.0 e-31 ≤ h ≤ 1.0 e-18
1.0 e-31 ≤ h ≤ 1.0 e-18
1.0 e-31 ≤ h ≤ 1.0 e-18
-2
0
-1
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Commands Summary
EXTERNALCLOCK FREQUENCY
Please see the Overview and Theory sub-sections under the EXTERNALCLOCK command to understand the steps
involved in using an optional external oscillator with a MiLLennium GPSCard.
For the chosen oscillator, one must select the clock rate using the EXTERNALCLOCK FREQUENCY command. The
MiLLennium GPSCard only accepts a 5 MHz or 10 MHz external input. An internal frequency synthesizer
converts this input to 20 MHz, the actual clock rate required by the MiLLennium GPSCard (and that which is
generated by its on-board VCTCXO).
Syntax:
EXTERNALCLOCK FREQUENCY clock rate
Command
EXTERNALCLOCK FREQUENCY
clock rate
Range
Description
Default
-
5 or 10
Set clock rate to 5 MHz or 10 MHz (Will 10
not allow values other than 5 or 10)
Example:
externalclock frequency 5
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Commands Summary
FIX HEIGHT
This command configures the GPSCard in 2D mode with its height constrained to a given value. The command
would be used mainly in marine applications where height in relation to mean sea level may be considered to be
approximately constant. The height entered using this command is always referenced to the geoid (mean sea level,
see the PRTKA/B log in Chapter 4 and Appendix D) and uses units of meters. The FIX HEIGHT command will override
any previous FIX HEIGHT or FIX POSITION command and disables the output of differential corrections. The receiver
is capable of receiving and applying differential corrections from a reference station while FIX HEIGHT is in effect.
Use the UNFIX command to disable the current FIX command. No special solution status is reported in the POSA/B
or PRTKA/B logs for a 2 dimensional solution. This mode is detected by the standard deviation of the height being
0.001m.
Syntax:
FIX HEIGHT value
Syntax
FIX HEIGHT
value
Range Value
Description
Default
-
Command
unfix
height
-1,000.0 to 20,000,000.0
Height in metres above mean sea level
auto
The receiver will automatically fix the height at the last calculated value if the
number of satellites available is insufficient for a 3-D solution, to provide a 2-D
solution. Height calculation will resume when the number of satellites available
returns to 4 or more. The use of the UNFIX command, or a different FIX
command will disable the automatic fix height mode. It is disabled by default.
Example:
or
fix height 4.567
fix height auto
REMEMBER: Any error in the height estimate will cause an error in the position computed of the same order
of magnitude or higher. For example, if the user fixed height to zero and the antenna was installed
on a 20 meter mast, the position can be expected to be in error by 10 to 60 meters, depending on
the geometry of the satellites. This command should only be used when absolutely necessary, i.e.,
when only three satellites are visible.
NOTE: This command only affects pseudorange corrections and solutions, and so has no meaning within the
context of RT-2 and RT-20.
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Commands Summary
FIX POSITION
Invoking this command will result in the GPSCard position being held fixed. A computation will be done to solve
local clock offset, pseudorange, and pseudorange differential corrections. This mode of operation can be used for
time transfer applications where the position is fixed and accurate GPS time output is required (see the CLKA/B and
TM1A/B logs, Appendix D for time data).
As well, this command must be properly initialized before the GPSCard can operate as a GPS pseudorange reference
station. Once initialized, the receiver will compute pseudorange differential corrections for each satellite being
tracked. The computed differential corrections can then be output to remote stations by utilizing any of the
following GPSCard differential corrections data log formats: RTCM, RTCMA, RTCMB, CMR, RTCA, RTCAA or RTCAB.
The reference station servicing RT-20 remote receivers must log RTCM3 and RTCM59(N) pseudorange and carrier
phase observation data in order for the RT-20 remote receiver to compute double difference carrier phase solutions.
The values entered into the FIX POSITION command should reflect the precise position of the reference station
antenna phase centre. Any errors in the FIX POSITION coordinates will directly bias the pseudorange corrections
calculated by the reference receiver.
The GPSCard performs all internal computations based on WGS84 and the datum command is defaulted as such.
The datum in which you choose to operate (by changing the DATUM command) will internally be converted to and
from WGS84. Therefore, all differential corrections are based on WGS84, regardless of your operating datum.
The GPSCard will begin logging differential data while tracking as few as three healthy satellites. See Appendix A
for further discussions on differential positioning.
The FIX POSITION command will override any previous FIX HEIGHT or FIX POSITION command settings. Use the
UNFIX command to disable the FIX POSITION setting.
Syntax:
FIX POSITION lat
lon
height station id
Description
[RTCM stn health]
Syntax
Range Value
Default
Example
FIX POSITION
lat
-
Command
unfix
fix position
0 to ± 90.0
Latitude (in degrees/decimal degrees)
51.3455323
(Up to 8 decimal places are shown in the RCCA of fixed reference station antenna in
log but more precision is determined internally) currentdatum. Anegativesignimplies
South latitude.
lon
0 to ± 360.0
Longitude (in degrees) of fixed
-114.289534
(Up to 8 decimal places are shown in the RCCA reference station antenna in current
log but more precision is determined internally) datum. A negative sign implies West
longitude.
height
-1,000 to 20,000,000
Height (in metres) above the geoid of
reference station in current datum.
1201.123
1002
station id
0 to 1023 (10 bits) for RTCM output
“xxxx” for RTCA output
Specify a reference Station
identification number (optional entry)
where ”xxxx” are four alphanumeric characters, (see SETDGPSID)
entered between double quotes. For CMR, the
station ID should be < 31.
RTCM
0-7
SpecifyRTCMreferencestationhealth
6
0
reference
station health
where 0-5 Specified by user
(optional)
(This field will only be reported in
RTCM message header - word 2.)
6
Reference station
transmission not monitored
Reference station not working
7
Example:
fix position 51.3455323,-114.289534,1201.123,1002,0
The above example configures the receiver as a reference station with fixed coordinates of:
Latitude N 51º 20' 43.9163" (WGS84 or local datum)
Longitude
W 114º 17' 22.3224"
Height above sea level
Station ID
RTCM health
1201.123 meters
1002
0
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Commands Summary
FIX VELOCITY
This command supports INS (Inertial Navigation System) integration. It accepts ECEF XYZ velocity values in units
of meters per second (m/s). This information is only used by the tracking loops of the receiver to aid in reacquisition
of satellites after loss of lock, otherwise it is ignored. It is not used in the position solution and velocity calculations.
This command is only useful for very high dynamics where expected velocity changes during the signal blockage
of more than 100 meters per second can occur. See Figure D-2 for ECEF definitions. The UNFIX command is used
to clear the effects of the FIX VELOCITY command. The FIX VELOCITY command will override any previous FIX
HEIGHT or FIX POSITION command. Use the UNFIX command to disable the current FIX command.
Syntax:
FIX VELOCITY vx
vy
vz
Syntax
Range Value
Description
Default
Example
fix velocity
315
FIX VELOCITY
-
Command
unfix
vx
vy
vz
±999.99
±999.99
±999.99
X = Antenna Velocity (ECEF) in the X direction [m/s].
Y = Antenna Velocity (ECEF) in the Y direction [m/s].
Z = Antenna Velocity (ECEF) in the Z direction [m/s].
212
150
Example:
fix velocity 315,212,150
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Commands Summary
FREQUENCY_OUT
This command allows the user to specify the frequency of the output pulse train available at the variable frequency
(VARF) pin of the I/O strobe connector. This command has no effect on the operation of the GPSCard; it is only
provided for user-determined applications.
The frequency (in Hertz) is calculated according to formulas which require two input parameters (k and p), such
that:
if k =1 or p =1:
VARF = 0
Fs × 19, 999
-----------------------------------
if k ≠ 1, p ≠ 1:
VARF =
20, 000 × k × p
Where:
Fs is the TCXO frequency = 20.000 MHz
k is an integer from 2 to 65536
p is an integer from 2 to 1024
The possible range of output frequencies is 0 - 5 MHz.
The resultant waveform is composed of active-high pulses with a repetition rate as defined above, and a jitter of 50
ns unless k equals 19 999, see the table below for Syntax 1.
The pulse width (seconds) =
1 ⁄ [(Fs × 19999) ⁄ (20000 × k)]
The command has two syntactical forms. One is to define a frequency, and the other is to disable this function.
Syntax 1:
FREQUENCY_OUT K P
For Jitter Free
Operation
Command
Range Values
Description
FREQUENCY_OUT
-
-
Command
K
P
1 - 65 536
1 - 1 024
19 999
2 - 1 024
Variable integer
Variable integer
Example:
frequency_out 4,8
Syntax 2:
FREQUENCY_OUT keyword
Command
FREQUENCY_OUT
keyword
Range Values
Description
-
Command
The keyword “DISABLE” is the only one defined at this time.
disable
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Commands Summary
FRESET
This command clears all data which is stored in non-volatile memory. Such data includes the almanac, satellite
channel configuration, and any user-specific configurations. The GPSCard is forced to reset and will start up with
factory defaults.
See also the CRESET, where the differences between these three commands are explained, and RESET commands.
Syntax:
FRESET
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Commands Summary
HELP
This command provides you with on-line help. The command, with no options, gives a complete list of the valid
system commands. For detailed help on any command, append the optional command name to the HELP command.
Syntax:
HELP option
OR:
?
option
Syntax Range Value
HELP (or ?)
Description
-
Entering HELP without an option will list all valid command options.
Can be any valid system command. Information about the command entered will be displayed.
option
See Figure C-1
Example:
help dynamics
Figure C-1 shows the screen display of the HELP command as it would be seen if you were using NovAtel’s
graphical interface program GPSolution. Figure C-2 shows a specific example of the ASSIGN command appended
to the HELP command.
Figure C-1 HELP Command Screen Display
Com1> help
?-Online Command Help
ACCEPT -Accept Datatypes
ANTENNAPOWER -Antenna Power Control
CLOCKADJUST -Adjust 1pps
ASSIGN -Assign PRN To a Chan.
COM1
-Initialize Port 1
COM2
-Initialize Port 2
COM1_DTR -DTR Control on Port 1
COM1_RTS -RTS Control on Port 1
CONFIG -Configure Satellites
CSMOOTH -Carrier Smoothing
DGPSTIMEOUT -Max. aye of DGPS data
DYNAMICS -Set Dynamics
COM2_DTR -DTR Control on Port 2
C0M2_RTS -RTS Control on Port 2
CRESET -Factory Config Reset
DATUM -Choose a DATUM Type
DIFF_PROTOCOL -Diff.. protocol control
ECUTOFF -Elevation Cutoff Angle
EXTERNALCLOCK -Specify Clock type
RESET -Factory Card Reset
FIX
-Set Antenna Coord..
FREQUENCY OUT -Variable Freq. Output
LOCKOUT -Lock Out Satellite
MAGVAR -Set Magnetic Variation.on
POSAVE -Position Averaging
RESETHEALTH -Reset PRN Health
RESETRT20 -Reset RT20 algorithm
RINEX -RINEX( Configuration
RTCMRULE -RTCM Bit Rule
HELP
LOG
-Online Command Help
-Choose Date Logging
MESSAGES -Error Messages On/Off
RESET -Hardware Reset
RESETHEALTHALL -Reset All PRE Health
RTKMODE -Set RTK parameters
RTCM16T -Input Type l6 Message
SAVEALMA -Save Almanac & ION/UTC
SAVECONFIG -Save User Config.
SENDHEX-Send hex to a port
SETHEALTH -Overr.ide PRN Health
SETNAV -Set a Destination
UNASSIGN -Un-Assign a Channel
UNDULATION-Choose Undulation
UNLOCKOUT -Restore Satellite
UNLOG -Kill a Data Log
SEND
-Send string to a port
SETDGPSID -Set the Station ID
SETL10FFSET -Set Ll PSR Offset
SETTIMESYNC -Enable/Disable Timesync
UNASSIGNALL -Un-Assign All Channels
UNFIX
-Remove Recvr. FIX(ed)
UNLOCKOUTALL -Select All Satellites
UNLOGALL -Kill all Data Logs
USERDATUM -User Defined DATUM
Com1>
VERSION -Current Software Vet.
Figure C-2 Appended Command Screen Display
COM2> help assign
ASSIGN Channel_no, PRN, Doppler, Dop_window
Assign a prn to a channel
where:
COM2>
Channel_no
PRN
= A channel number from 0-23
= A satellite PRN number from 1-32
Doppler
Dop_window
= Current satellite doppler offset (-100000 to +100000 Hz)
= Uncertainty in doppler estimate (0 to 10000 Hz)
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Commands Summary
IONOMODEL
WAAS
This command allows the user to decide what ionospheric corrections the card uses. This command currently does
not effect the ionospheric model that is used when the card is operating in RTK mode. Additional range values are
reserved for future use.
The MiLLennium by default computes ionospheric corrections using L1 & L2 signals; to use the ionospheric
corrections issued by the WAAS GEO satellite, you need to issue the IONOMODEL WAAS command.
Syntax:
IONOMODEL keyword
Syntax
IONOMODEL
keyword
Range Value
Description
-
Command
WAAS
- Card will use Ionospheric corrections from WAAS broadcast messages.
You must first issue the following commands for this command to work:.
config waascorr
waascorrection enable
CALCULATED
- Card will calculate its own Ionospheric corrections.
Note: You cannot change GPSCard modes on the fly as the once a CONFIG command is issued the card resets
itself and start the new mode requested.
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Commands Summary
LOCKOUT
This command will prevent the GPSCard from using a satellite by de-weighting its range in the solution
computations. Note that the LOCKOUT command does not prevent the GPSCard from tracking an undesirable
satellite. This command must be repeated for each satellite to be locked out.
See also the UNLOCKOUT and UNLOCKOUTALL commands.
Syntax:
LOCKOUT prn
Syntax
LOCKOUT
prn
Range Value
Description
Default
-
Command
A single satellite PRN integer number to be locked out
unlockoutall
1 - 32
Example:
lockout 8
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Commands Summary
LOG
Many different types of data can be logged using several different methods of triggering the log events. Every log
element can be directed to either the COM1 or COM2 ports. If a selected log element is to be directed to all the ports,
then separate LOG commands are required to control them. The ONTIME trigger option requires the addition of the
period parameter and optionally allows input of the offset parameter. See Chapter 3 and Appendix D for further
information and a complete list of ASCII and Binary data log structures.
The optional parameter {hold} will prevent a log from being removed when the UNLOGALL command is issued. To
remove a log which was invoked using the {hold} parameter requires the specific use of the UNLOG command.
The [port] parameter is optional. If [port] is not specified, [port] is defaulted to the port that the command was
received on.
Syntax:
LOG [port]
datatype [trigger]
[period] [offset] {hold}
Example:
log com1,posa,ontime,60,1,hold
The above example will cause the POSA log to be logged to COM port 1, recurring every 60 seconds, offset by one
second, and with the {hold} parameter set so that logging would not be disrupted by the UNLOGALL command.
To send a log only one time, the trigger option can be ignored.
Example:
log com1 posa
log posa
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Commands Summary
MAGVAR
The GPSCard computes directions referenced to True North. Use this command (magnetic variation correction) if
you intend to navigate in agreement with magnetic compass bearings. The correction value entered here will cause
the "bearing" field of the NAVA/B and GPVTG logs to report bearing in degrees Magnetic. The magnetic variation
correction is also reported in the GPRMC log. The GPSCard will compute the magnetic variation correction if you
use the auto option.
Syntax:
MAGVAR correction
OR
[std_dev]
MAGVAR auto
Syntax
MAGVAR
correction
Range Value
Description
Default
-
Command
± 0 - 180
The magnetic variation correction for the area of navigation in units of degrees. 0.0
Magnetic bearing = True bearing + Magnetic Variation Correction
See Figure C-3.
std_dev
auto
± 0 - 180
Option: the estimated accuracy of the magnetic correction entered(in degrees).
This option is currently not applicable to this product.
The GPSCard calculates valuesof magnetic variation for given values of latitude,
longitude and time using the International Geomagnetic Reference Field (IGRF)
95 spherical harmonic coefficients, and IGRF time corrections to the harmonic
coefficients.
Example:
magvar +15.0
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Commands Summary
MESSAGES
The MESSAGES command is used to disable the port prompt and error message reporting from a specified port. This
feature can be useful if the port is connected to a modem or other device that responds with data the GPSCard does
not recognize. See Chapter 3 for further information on using this command with Special Pass-Through Logs.
Syntax:
MESSAGES port
option
Syntax
Range Value
Description
Default
MESSAGES
port
-
Command
MESSAGES
COM1, COM2 or all
ON or OFF
Specifies the port being controlled
-
option
Enable or disable port prompt and error message reporting
ON
Example:
messages com1,off
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Commands Summary
POSAVE
This command implements position averaging for reference stations. Position averaging will continue for a
specified number of hours or until the averaged position is within specified accuracy limits. Averaging will stop
when the time limit or the horizontal standard deviation limit or the vertical standard deviation limit is achieved.
When averaging is complete, the FIX POSITION command will automatically be invoked.
If the maximum time is set to 1 hour or larger, positions will be averaged every 10 minutes and the standard
deviations reported in the PAVA/B log should be correct. If the maximum time is set to less than 1 hour, positions
will be averaged once per minute and the standard deviations reported in the log will likely not be accurate; also,
the optional horizontal and vertical standard deviation limits cannot be used.
One could initiate differential logging, then issue the POSAVE command followed by the SAVECONFIG command.
This will cause the GPSCard to average positions after every power-on or reset, then invoke the FIX POSITION
command to enable it to send differential corrections.
Syntax:
POSAVE maxtime maxhorstd maxverstd
Command
POSAVE
Range Values
Description
-
Command
maxtime
0.025 - 100
Maximum amount of time that positions are to be
averaged (hours). 1.5 to 60 minutes
mashorstd
maxverstd
0.1 - 100
0.1 - 100
Option: desired horizontal standard deviation (m)
Option: desired vertical standard deviation (m)
Example:
posave 2,3,4
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Commands Summary
RESET
This command performs a hardware reset. Following a RESET command, the GPSCard will initiate a cold-start
bootup. Therefore, the receiver configuration will revert to the factory default if no user configuration was saved
or the last SAVECONFIG settings.
Syntax:
RESET
See also the CRESET, where the differences between these three commands are explained, and FRESET commands.
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Commands Summary
RESETHEALTH
This command cancels the SETHEALTH command and restores the health of a satellite to the broadcast value
contained in the almanac and ephemeris data.
Syntax:
RESETHEALTH prn
Syntax
RESETHEALTH
prn
Range Value
Description
-
Command
The PRN integer number of the satellite to be restored.
1 - 32
Example:
resethealth 4
RESETHEALTHALL
This command resets the health of all satellites to the broadcast values contained in the almanac and ephemeris
data.
Syntax:
RESETHEALTHALL
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Commands Summary
RINEX
Receiver-Independent Exchange Format
The RINEX format is a broadly-accepted, receiver-independent format for storing GPS data. It features a non-
proprietary ASCII file format that can be used to combine or process data generated by receivers made by different
manufacturers. RINEX was originally developed at the Astronomical Institute of the University of Berne. Version
2, containing the latest major changes, appeared in 1990; subsequently, minor refinements were added in 1993. To
date, there are three different RINEX file types observation files, broadcast navigation message files and
meteorological data files.
Please see Chapter 4 for further details.
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Commands Summary
RTCM16T
This is a NovAtel command relating to the RTCM Standard ASCII message that can be sent out in RTCM Type 16
format. Once created, the RTCM16T message can be viewed in the RCCA command settings list. The text message
can also be logged using the RTCM16 or RTCM16T log option. This command will limit the input message length to
a maximum of 90 ASCII characters.
See Chapter 4, for related topics.
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Commands Summary
RTKMODE
This command sets up the RTK (RT-2 or RT-20) mode. Invoking this command allows you to set different
parameters and control the operation of the RTK system. The RTKMODE command is actually a family of
commands; a description of the various arguments and options is as follows. Some arguments require data input,
while others do not.
Certain arguments can be used only at the reference station, and others only at the remote station. The structure of
the syntax is shown below, followed by a detailed description of each argument.
Syntax - Reference Station
For RTCA-format messaging only:
RTKMODE sv_entries
4to 20
RTKMODE elev_mask 0to 90
Command
Argument
Data Range
Default
RTKMODE
sv_entries
elev_mask
4 to 20
0 to 90
12
2
For RTCM-format messaging only:
RTKMODE rtcmver 2.1 or 2.2
Command
Argument
Data Range
Default
2.2
RTKMODE
rtcmver
2.1 or 2.2
Syntax - Remote Station (for RTCA, RTCM or CMR-format messaging):
RTKMODE default
RTKMODE enable
RTKMODE disable
RTKMODE reset
RTKMODE auto
RTKMODE static
RTKMODE kinematic
RTKMODE fixed
RTKMODE float
RTKMODE unknown_baselines
RTKMODE known_llh_position
RTKMODE know_ecef_baseline
lat lon
∆x ∆y
hgt
[2σ]
[2σ]
[m/e]
∆z
RTKMODE elev_mask
0 to 90
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Commands Summary
Command
RTKMODE
Argument
Default Argument
default
Data Range
default
enable or disable
reset
enable
auto, static or kinematic
fixed or float
auto
fixed
unknown_baseline,
unknown_baseline
known_llh_position lat,lon,hgt,[2σ],[m/e] or
lat: 0 to ± 90
lon: 0 to ± 360
hgt: -1000 to +20 000 000
2σ: 0 to 0.03
m/e: m or e (m = default)
known_ecef_baseline ∆x, ∆y,∆z,[2σ]
2
2
2
(∆x) + (∆y) +(∆z)
2
≤ (1 000 000)
2σ: 0 to 0.03
Below is additional information for each argument:
Station
Reference
Command
Argument
elev_mask
Data
elevation (range 0 to 90, default = 2)
rtkmode
RTKMODE ELEV_MASK ELEVATION causes transmission of observations for satellites above this elevation
angle only. The elevation angle has units of degrees, and can be a decimal fraction value. At this time, this com-
mand affects RTCAOBS (RTCA Type 7) messages but not RTCM or CMR messages; if RTCM-format messag-
ing is being used, then observations for a certain satellite are transmitted as soon as it becomes visible.
Example:
rtkmode elev_mask 10.5
Remote
rtkmode
elev_mask
elevation (range 0 to 90)
When RTKMODE ELEV_MASK ELEVATION is issued at the remote, it controls the elevation angle above which satellites
will be fully weighted. A value less than 5° will be ignored. This command can be used at the remote regardless of the type of inter-receiver
messages use.
Station
Remote
Command
Argument
rtkmode
default
RTKMODE DEFAULT, when issued at the remote station, all RTK parameters are returned to their default values.
Station
Remote
Command
Argument
rtkmode
enable (default)
disable
RTKMODE ENABLE, when issued at the remote station, turns on its ability to receive and process RTCA or RTCM messages. RTKMODE
DISABLE exits the RTK positioning mode.
Station
Reference
Command
Argument
Data
rtkmode
rtcmver
2.1
2.2 (default)
For RTCM-format messaging only, at the reference station, when issued determines what RTCM version to use.
Note: The remote station can use either version 2.1 or 2.2 without the use of this command.
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Commands Summary
Station
Remote
Command
Argument
unknown_baseline (default)
known_llh_position
Data
rtkmode
lat,lon,height,[2σ],[m/e]
∆x, ∆y, ∆z,[2σ]
known_ecef_baseline
RTKMODE UNKNOWN_BASELINE prevents the RTK system from using any baseline information in the initial
calculation of ambiguities. It cancels the effect of the RTKMODE KNOWN_LLH_POSITION or RTKMODE
KNOWN_ECEF_BASELINE command. It indicates to the RT-2 software that the previously entered baseline can no
longer be considered valid, usually because the antenna is starting to move.
RTKMODE KNOWN_LLH_POSITION LAT,LON,HEIGHT,[2σ],[M/E] requires the latitude, longitude and
height of the initial remote station antenna location. It can be used to initialize the RT–2 algorithms from a known
antenna position. It speeds up ambiguity resolution by indicating to the RT-2 software the exact length of the vector
between the remote and reference station antennas. It only affects the operation of an RT-2 system on baselines not
exceeding 30 km. LAT requires a decimal fraction format; a negative sign implies South latitude. LON requires a
decimal fraction format; a negative sign implies West longitude. HEIGHT (in meters) can refer either to mean sea level
(default) or to an ellipsoid. The optional 2σ defines the accuracy (2 sigma, 3 dimensional) of the input position, in
meters; it must be 0.03 m or less to cause the RT-2 algorithms to undergo a forced initialization to fixed integer
ambiguities. If no value is entered, a default value of 0.30 m is assumed; this will not cause an initialization to occur.
The optional M or E refers to the height: if “M” is entered, the height will be assumed to be above mean sea level (MSL).
Note that when an MSL height is entered, it will be converted to ellipsoidal height using the NovAtel internal undulation
table or the last value entered with the “UNDULATION” command. You may directly indicate an ellipsoidal height by
using the optional “E” flag.
Example:
rtkmode known_llh_position 51.113618,-114.04358,1059.15,0.01,e
RTKMODE KNOWN_ECEF_BASELINE ∆X,∆Y,∆Z,[2σ] can be used to initialize the RT–2 algorithms from a
known ECEF baseline. The RT-2 system uses this to initialize its ambiguities. It only affects the operation of an RT-2
system on baselines not exceeding 30 km. The ∆X,∆Y,∆Z values represent the remote station’s position minus the ref-
erence position, along each axis, in meters. The optional 2σ defines the accuracy (2 sigma, 3 dimensional) of the input
baseline, in meters; it must be 0.03 m or less to cause the RT-2 algorithms to do a forced initialization to fixed integer
ambiguities. If no value is entered, a default value of 0.30 m is assumed; this will not cause an initialization to occur.
Example:
rtkmode known_ecef_baseline 3583,2165,567,0.02
NOTE: You must be very careful when using these last two commands; erroneous input will cause poor performance
and/or erroneous output. It is also very important to follow these command with an RTKMODE
UNKNOWN_BASELINE command before any motion begins.
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Commands Summary
Station
Remote
Command
Argument
rtkmode
auto (default)
static
kinematic
RTKMODE AUTO configures the RTK system to automatically detect motion. It is the default mode. It will
reliably detect motion of 2.5 cm/sec or greater. If you are undergoing motion slower than this which covers more
than 2 cm, you should use the manual mode selection commands (static and kinematic).
RTKMODE STATIC forces the RTK software to treat the remote station as though it were stationary, regardless
of the output of the motion detector.
Note: For reliable performance the antenna should not move more than 1 - 2 cm when in static mode.
RTKMODE KINEMATIC forces the RTK software to treat the remote station as though it were in motion,
regardless of the output of the motion detector. If the remote station is undergoing very slow steady motion (<
2.5 cm/sec for more than 5 seconds), you should declare KINEMATIC mode to prevent inaccurate results and
possible resets.
Station
Remote
Command
Argument
rtkmode
fixed (default)
float
RTKMODE FIXED tells the RTK system to use fixed discrete ambiguities whenever the system is capable and
can do so reliably; it may never do so for long baselines or poor geometries. Only RT-2 systems are capable of
fixing ambiguities, so issuing this command on an RT-20 system will have no effect.
RTKMODE FLOAT causes the system to compute only a floating ambiguity solution. L2 data will be used
along with L1 data if the system is capable of generating L2 data.
You can force the RT-2 software to not fix ambiguities when it normally would, but you cannot force it to fix
ambiguities when it normally wouldn’t.
Station
Remote
Command
Argument
rtkmode
reset
RTKMODE RESET causes the RTK algorithm (RT-20 or RT-2, whichever is active) to undergo a complete reset, forcing the system to
restart the ambiguity resolution calculations.
Station
Reference
Command
Argument
Data
rtkmode
sv_entries
number (range 4 to 20, default = 12)
RTKMODE SV_ENTRIES NUMBER causes the number of satellite measurements to be limited to the number
indicated. NUMBER refers to the number of PRNs transmitted by the reference station; each PRN can have either
an L1-only measurement or an L1/L2 pair of measurements. At this time, this command affects RTCAOBS
(RTCA Type 7) messages but not RTCM or CMR messages; if RTCM-format messaging is being used, then
observations for all visible satellites are transmitted.
Example:
rtkmode sv_entries 8
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Commands Summary
SAVEALMA
This command saves the latest almanac in non-volatile memory.
The option ONNEW is the default; if a different setting is used, a SAVECONFIG command must be issued or else
ONNEW will resume after a reset.
Bit 21 in the receiver self-test status word (see Table D-5, Page 196) indicates whether the latest almanac received
by the GPS receiver is newer than the almanac saved in non-volatile memory (NVM).
Syntax:
SAVEALMA
option
Command
SAVEALMA
option
Range Values
Description
Default
onnew
-
Command
onnew
Each almanac is saved in NVM upon reception if it is newer than the one already
stored. This will occur continuously.
stop
Stops auto saving.
disable ➀
Stops auto saving and prevents the use of the almanac, saved in NVM, on startup.
➀The disable option must be followed by the SAVECONFIG command to have an effect.
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Commands Summary
SEND
This command is used to send ASCII printable data from the COM1 or COM2 or disk file to a specified
communications port. This is a one-time command, therefore the data message must be preceded by the SEND
command followed by the <Enter> key (<CR><LF>) each time you wish to send data. (Remember to use the
MESSAGES command to disable error reporting whenever two GPSCards are connected together via the COM ports.)
Syntax:
SEND to-port
data
Range Value
Syntax
SEND
Description
Command
Port option
ASCII data
to-port
COM1, COM2
data
up to 100 characters
Scenario: Assume that you are operating GPSCards as reference and remote stations. It could also be assumed
that the reference station is unattended but operational and you wish to control it from the remote station. From the
remote station, you could establish the data link and command the reference station GPSCard to send differential
corrections.
Figure C-4 Using SEND Command
$PVAA data log...
c
o
n
o
o
COM1
COM 1
COM 2
COM 2
messages com1 off
send com1 log com1 pvaa ontime 5
Serial Cables
Host PC - Rover
Rover station is commanding Reference
to send PVAA differential logs
Host PC - Reference
(Operational with position fixed)
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Commands Summary
SENDHEX
This command is like the SEND command but is used to send non-printable characters expressed as hexadecimal
pairs.
Syntax:
SENDHEX to-port data
Syntax
SENDHEX
to-port
Range Value
Description
Command
COM1, COM2
Port option
ASCII data
data
•
•
•
even number of ASCII characters from set of 0-9, A-F
spaces allowed between pairs of characters
carriage return & line feed provided by entering
ODOA at end of string
•
maximum number of characters limited to about 1400
characters by command interpreter buffer (2800
ASCII characters pairs)
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Commands Summary
SETDGPSID
This command is used to enter a station ID. Once set, the receiver will only accept differential corrections from a
station whose ID matches the set station ID. It is typically used when a station has data links containing RTCM or
RTCA messages from several stations. By entering a specific station ID, the operator can select which station to
listen to. Having set a station ID, incoming, RTCM, RTCMA, RTCA, RTCAA, and RTCAB messages will be received
from only that station. When a valid station ID is entered, an improved data synchronization algorithm will be used.
It is recommended to always set the station ID. This command can also be used to set the station ID for a GPSCard
reference station. See FIX POSITION 4th parameter (station ID).
Syntax:
SETDGPSID
SETDGPSID
station ID #
all
Syntax
SETDGPSID
station ID #
Range Value
Description
Default
Command
0 - 1023
Reference station ID number for RTCM
all
or
“xxxx”
or
Reference station name for RTCA where ”xxxx” are four
alphanumeric characters, entered between double quotes
0 - 31
or
Reference station ID number for CMR
all
Accepts differential corrections from any station
Example 1: SETDGPSID 1023
Example 2: SETDGPSID “abcd”
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Commands Summary
SETHEALTH
This command permits you the flexibility to override the broadcast health of a satellite. Under certain conditions
and applications, it may be desirable to track and use information from a GPS satellite even though its health has
been set bad by the GPS control segment. To SETHEALTH for more than one satellite, the command must be re-issued
for each satellite.
IMPORTANT: There is usually a reason when the GPS Control Segment sets a satellite to bad health
condition. If you decide to ignore the health warnings and use the satellite information, UNPREDICTABLE
ERRORS MAY OCCUR.
Syntax:
SETHEALTH prn health
Syntax
SETHEALTH
prn
Range Value
Description
Command
Default
-
resethealthall
1 - 32
A satellite PRN integer number
Desired health;
health
good or bad
Example:
sethealth 4,good
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Commands Summary
SETL1OFFSET
The characteristic signal delays introduced by the antenna, coaxial cable and GPSCard RF section will vary from
one system configuration to another. These delays are measurable using external test equipment. For applications
which involve very precise time transfer, or where ranges are used from multiple receivers, it may be necessary to
add an offset to the L1 pseudorange to compensate for these delays. This is equivalent to a system calibration in
that it corrects for inter-receiver range bias.
It does not affect the output position, and it is unrelated to data latencies.
NOTE: This feature is to be used by advanced users only.
Its intended application is for use in multi-card systems, in which case the clocks on the different
GPSCards must be synchronized. The command is not necessary for most applications.
Syntax:
SETL1OFFSET distance
Command
SETL1OFFSET
distance
Range Values
Description
-
-10 to +10
Pseudorange offset (m)
Example:
setl1offset 1.348693
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Commands Summary
SETNAV
This command permits entry of one set of navigation waypoints (see Figure C-5). The origin (FROM) and
destination (TO) waypoint coordinates entered are considered on the ellipsoidal surface of the current datum
(default WGS84). Once SETNAV has been set, you can monitor the navigation calculations and progress by observing
the NAVA/B, GPRMB, and GPZTG log messages.
Track offset is the perpendicular distance from the great circle line drawn between the FROM lat-lon and TO lat-lon
waypoints. It establishes the desired navigation path, or track, that runs parallel to the great circle line, which now
becomes the offset track, and is set by entering the track offset value in meters. A negative track offset value
indicates that the offset track is to the left of the great circle line track. A positive track offset value (no sign
required) indicates the offset track is to the right of the great circle line track (looking from origin to destination).
See Figure C-5 for clarification.
Syntax:
SETNAV from-lat
track offset
SETNAV disable
from-lon
to-lat
to-lon
from-port
to-port
Syntax
SETNAV
from-lat
Range Value
Description
Default
Example
setnav
-
Command
0± 90
Origin latitude in units of degrees/decimal degrees. A negative disable
sign implies South latitude. No sign implies North latitude.
51.1516
from-lon
0± 360
Origin longitude in units of degrees/decimal degrees. A
negative sign implies West longitude. No sign implies East
longitude.
-114.16263
to-lat
0± 90
Destination latitude in units of degrees/decimal degrees
Destination longitude in units of degrees/decimal degrees
51.16263
-114.1516
-125.23
to-lon
0± 360
0± 1000
track offset
Waypoint great circle line offset (in kilometers); establishes
offset track; positive indicates right of great circle line; negative
indicates left of great circle line
from-port
to-port
1 to 5 characters
1 to 5 characters
Optional ASCII station name
Optional ASCII station name
from
to
Example:
setnav 51.1516,-114.16263,51.16263,-114.1516,-125.23,from,to
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Commands Summary
Figure C-5
Illustration of SETNAV Parameters
Reference
Description
1
2
3
4
5
6
7
TO, lat-lon
X-Track perpendicular reference point
Current GPS position
A-Track perpendicular reference point
X-Track (cross-track)
A-Track (along track)
Distance and bearing from 3 to 1
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Commands Summary
SETTIMESYNC
This command enables or disables time synchronization, which permits two GPSCards in a master/slave
relationship to be synchronized to a common external clock for range comparisons. By default, this function is
disabled.
With SETTIMESYNC enabled, a slave unit is able to interpret injected ($)TM1A/B data messages; for more
information, please refer to the comments relating to the ($)TM1A/B special data messages, and the 1PPS signal.
Syntax:
SETTIMESYNC flag
Command
SETTIMESYNC
flag
Range of Values
Description
Default
-
enable or disable
Enable or disable time synchronization disable
Example:
settimesync enable
NOTE: This command is intended for advanced users of GPS only.
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Commands Summary
UNASSIGN
This command cancels a previously issued ASSIGN command and the channel reverts to automatic control. If a
channel has reached state 4 (PLL), the satellite being tracked will not be dropped when the UNASSIGN command is
7
issued, unless it is below the elevation cutoff angle, and there are healthy satellites above the ecutoff that are not
already assigned to other channels.
Syntax:
UNASSIGN channel
Syntax
UNASSIGN
channel
Range Value
Description
Default
-
Command
Reset channel to automatic search and acquisition mode
unassign 11
unassignall
0 - 11
Example:
UNASSIGNALL
This command cancels all previously issued ASSIGN commands for all channels. Tracking and control for each
channel reverts to automatic mode. If any of the channels have reached state 4 (PLL), the satellites being tracked
will not be dropped when the UNASSIGNALL command is issued, unless they are below the elevation cutoff angle,
and there are healthy satellites above the ecutoff that are not already assigned to other channels.
Syntax:
UNASSIGNALL
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Commands Summary
UNDULATION
This command permits you to either enter a specific geoidal undulation value or use the internal table of geoidal
undulations. The separation values only refer to the separation between the WGS84 ellipsoid and the geoid,
regardless of the datum chosen, see the PRTKA/B log in Chapter 3 and Appendix D.
Syntax:
UNDULATION separation
Syntax
UNDULATION
separation
Range Value
Description
Default
-
Command
table
Selects the internal table of undulations and ignores any previously entered value. The table
internal table utilizes OSU - 89B 1.5º x ~1.5º.
or
enter a value
A numeric entry that overrides the internal table with a value in meters.
Example 1:
undulation table
undulation -5.6
Example 2:
Please see Appendix A, A.2 Height Relationships for a description of the relationships in Figure C-6.
Figure C-6 Illustration of Undulation
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Commands Summary
UNFIX
This command removes all position constraints invoked with any of the FIX commands (FIX POSITION, FIX HEIGHT,
or FIX VELOCITY).
Syntax:
UNFIX
UNLOCKOUT
This command allows a satellite which has been previously locked out (LOCKOUT command) to be reinstated in the
solution computation. If more than one satellite is to be reinstated, this command must be reissued for each satellite
reinstatement.
Syntax:
UNLOCKOUT prn
Syntax
UNLOCKOUT
prn
Range Value
Description
Default
-
Command
A single satellite PRN to be reinstated
unlockoutall
1 - 32
Example:
unlockout 8
UNLOCKOUTALL
This command allows all satellites which have been previously locked out (LOCKOUT command) to be reinstated
in the solution computation.
Syntax:
UNLOCKOUTALL
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Commands Summary
UNLOG
This command permits you to remove a specific log request from the system.
The [port] parameter is optional. If [port] is not specified, it is defaulted to the port that the command was received
on. This feature eliminates the need for you to know which port you are communicating on if you want logs to
come back on the same port you are sending commands on.
Syntax:
UNLOG [port] datatype
Syntax
UNLOG
[port]
Range Value
Description
Default
-
Command
unlogall
COM1, COM2
any valid log
COMn port from which log originated
The name of the log to be disabled
datatype
Example:
unlog com1,posa
unlog posa
UNLOGALL
If [port] is specified (COM1 or COM2) this command disables all logs on the specified port only. All other ports
are unaffected. If [port] is not specified this command disables all logs on all ports.
Syntax:
UNLOGALL [port]
NOTE: This command does not disable logs that have the HOLD attribute (see description for LOG command).
To disable logs with the HOLD attribute, use the UNLOG command.
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Commands Summary
USERDATUM
This command permits entry of customized ellipsoidal datum parameters. Use this command in conjunction with
the DATUM command. The default setting is WGS84.
Syntax:
USERDATUM semi-major flattening dx dy dz rx ry rz scale
Syntax
Range Value
Description
Default
Example
userdatum
6378206.4
USERDATUM
semi-major
-
Command
min.
Datum Semi-major Axis (a) in metres
6378137.000
6300000.0
max.
6400000.0
flattening
dx,dy,dz
min.
max.
290.0
305.0
Reciprocal Flattening, 1/f = a/(a-b)
298.257223563
294.9786982
min.
max.
- 2000.0
2000.0
Datum offsets from WGS84 in meters:
These will be the translation values between your datum
and WGS84 (internal reference)
0.000,0.000,0.000 -12,147,192
rx,ry,rz
min.
max.
-10
10
Datum Rotation Angle about X, Y and Z axis (sec of arc): 0.000,0.000,0.000 0,0,0
These values will be the rotation between your datum
and WGS84
scale
min.
max.
-10
10
Scale value is the difference in ppm between your datum 0.000
and WGS84
0
Example:
userdatum 6378206.4,294.9786982,-12,147,192,0,0,0,0
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Commands Summary
VERSION
Use this command to determine the current software version of the GPSCard. The response to the VERSION
command is logged to the port from which the command originated.
Syntax:
VERSION
Command
VERSION
Response Syntax
S/N HW Rev
Card type
Model #
SW Rev
Date
Example:
version
OEM-3 MILLENRT2 ESN251448497 HW 3-1 SW 4.433/2.03 Feb 18/97
com1>
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Commands Summary
WAASCORRECTION
WAAS
This command allows you to have an affect on how the card handles WAAS corrections. The card will switch
automatically to Pseudorange Differential (RTCM or RTCA) or RTK if the appropriate corrections are being
received, regardless of the current setting.
The ability to incorporate the WAAS corrections into the position solution is not the default mode. First enter the
following command to put the card in WAAS mode:
config waascorr
Note: You cannot change GPSCard modes on the fly as the once a CONFIG command is issued the card resets
itself and start the new mode requested.
To enable the position solution corrections, you must issue the WAASCORRECTION ENABLE command.
Syntax:
WAASCORRECTION
keyword
Syntax
WAASCORRECTION
keyword
Range Value
Description
-
Command
ENABLE
DISABLE
- Card will use the WAAS corrections it receives.
- Card will not use the WAAS corrections that it receives.
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Logs summary
D
LOGS SUMMARY
D
LOGS SUMMARY
LOG DESCRIPTIONS
ALMA/B Decoded Almanac
This log contains the decoded almanac parameters from subframes four and five as received from the satellite with
the parity information removed and appropriate scaling applied. Multiple messages are transmitted, one for each
SV almanac collected. The Ionospheric Model parameters (IONA) and the UTC Time parameters (UTCA) are also
provided, following the last almanac records. For more information on Almanac data, refer to the GPS SPS Signal
Specification. (See Appendix F of this manual for References.)
MiLLennium cards will automatically save almanacs in their non-volatile memory (NVM), therefore creating an
almanac boot file would not be necessary.
ALMA
Structure:
$ALMA
prn ecc seconds
week rate-ra
cor-mean-motion
w
ra
A
Mo
a
a
f0
f1
incl-angle
health-4
health-5
health-alm *xx [CR][LF]
ALMA FORMAT
Field #
Field type
Data Description
Example
$ALMA
1
2
3
4
5
6
7
8
9
$ALMA
prn
Log header
Satellite PRN number for current message, dimensionless
Eccentricity, dimensionless
1
ecc
3.55577E-003
32768
seconds
week
rate-ra
ra
Almanac reference time, seconds into the week
Almanac reference week (GPS week number)
Rate of right ascension, radians
745
-7.8860E-009
-6.0052951E-002
-1.1824254E+000
1.67892137E+000
Right ascension, radians
w
Argument of perigee, radians
M
Mean anomaly, radians
o
10
11
12
13
14
15
16
17
18
19
a
Clock aging parameter, seconds
-1.8119E-005
f0
a
f1
Clock aging parameter, seconds/second
-3.6379E-012
cor-mean-motion Corrected mean motion, radians/second
1.45854965E-004
A
Semi-major axis, metres
2.65602281E+007
incl-angle
health-4
health-5
health-alm
*xx
Angle of inclination, radians
Anti-spoofing and SV config (subframe 4, page 25)
SV health, 6 bits/SV (subframe 4 or 5, page 25)
SV health, 8 bits (almanac)
Checksum
9.55576E-001
1
0
0
*20
[CR][LF]
Sentence terminator
[CR][LF]
1 - 19
1 - 19
1 - 11
1 - 11
$ALMA
$ALMA
$IONA
$UTCA
Next satellite PRN almanac message
Last satellite PRN almanac message
Ionospheric Model Parameters
UTC Time Parameters
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Logs summary
Example:
$ALMA,1,3.55577E-003,32768,745,-7.8860E-009,-6.0052951E-002,-1.1824254E+000,
1.67892137E+000,-1.8119E-005,-3.6379E-012,1.45854965E-004,2.65602281E+007,
9.55576E-001,1,0,0*20[CR][LF]
...
$ALMA,31,4.90665E-003,32768,745,-8.0460E-009,3.05762855E+000,6.14527459E-001,
1.69958217E+000,6.67572E-006,3.63797E-012,1.45861888E-004,2.65593876E+007,
9.61664E-001,1,0,0*13[CR][LF]
IONA FORMAT
Structure:
$IONA act
a1ot a2ot
b2ot b3ot
a3ot
*xx
bct
b1ot
Field #
[CR][LF]
Field type
Data Description
Example
1
2
3
4
$IONA
Log header
$IONA
act
Alpha constant term, seconds
Alpha 1st order term, sec/semicircle
1.0244548320770265E-008
1.4901161193847656E-008
-5.960464477539061E-008
a1ot
a2ot
2
Alpha 2nd order term, sec/(semic.)
5
a3ot
3
-1.192092895507812E-007
Alpha 3rd order term, sec/(semic.)
6
7
8
bct
Beta constant term, seconds
8.8064000000000017E+004
3.2768000000000010E+004
-1.966080000000001E+005
b1ot
b2ot
Beta 1st order term, sec/semicircle
2
Beta 2nd order term, sec/(semic.)
9
b3ot
3
-1.966080000000001E+005
Beta 3rd order term, sec/(semic.)
10
11
*xx
Checksum
*02
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$IONA,1.0244548320770265E-008,1.4901161193847656E-008,-5.960464477539061E-008,
-1.192092895507812E-007,8.8064000000000017E+004,3.2768000000000010E+004,
-1.966080000000001E+005,-1.966080000000001E+005*02[CR][LF]
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Logs summary
UTCA FORMAT
Structure:
$UTCA
pct
p1ot
data-ref
wk#-utc wk#-lset
[CR][LF]
delta-time
lsop
day #-lset *xx
Field #
Field type
Data Description
Log header
Example
1
$UTCA
pct
$UTCA
2
Polynomial constant term, seconds
Polynomial 1st order term, seconds/second
UTC data reference time, seconds
Week number of UTC reference, weeks
Week number for leap sec effect time, weeks
Delta time due to leap sec, seconds
For use when leap sec on past, seconds
Day number for leap sec effect time, days
Checksum
-2.235174179077148E-008
3
p1ot
-1.243449787580175E-014
4
data-ref
wk #-utc
wk #-lset
delta-time
lsop
32768
745
755
9
5
6
7
8
10
9
day #-lset
*xx
5
10
11
*37
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$UTCA,-2.235174179077148E-008,-1.243449787580175E-014,32768,745,755,9,10,5*37
[CR][LF]
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Logs summary
ALMB
ALMB FORMAT:
Message ID = 18
Message byte count = 120
Bytes Format
Field #
Field Type
Units
Offset
1
Sync
3
0
(header)
Checksum
1
4
4
4
8
8
4
8
8
8
8
8
3
Message ID
4
Message byte count
Satellite PRN number
Eccentricity
8
2
3
4
5
6
7
8
9
10
integer
double
double
integer
double
double
double
double
double
12
16
24
32
36
44
52
60
68
Almanac ref. time
Almanac ref. week
Omegadot - rate of right ascension
Right ascension
seconds
weeks
radians/second
radians
Argument of perigee
Mean anomaly
w
radians
Mo
radians
Clock aging parameter
a
seconds
f0
11
Clock aging parameter
a
8
double
seconds/second
76
f1
12
13
14
15
16
17
Corrected mean motion
8
8
8
4
4
4
double
double
double
integer
integer
integer
radians/second
meters
84
Semi-major axis
A
92
Angle of inclination
radians
100
108
112
116
Sv health from subframe 4, discrete
Sv health from subframe 5, discrete
Sv health from almanac, discrete
IONB FORMAT:
Field #
Message ID = 16
Message byte count = 76
Field Type
Bytes
Format
char
Units
Offset
1
Sync
3
0
(header)
Checksum
Message ID
1
4
4
8
8
8
char
3
integer
integer
double
double
double
4
Message byte count
Alpha constant term
Alpha 1st order term
Alpha 2nd order term
8
2
3
4
seconds
12
20
28
sec/semicircle
2
sec/(semic.)
5
Alpha 3rd order term
8
double
3
36
sec/(semic.)
6
7
8
Beta constant term
Beta 1st order term
Beta 2nd order term
8
8
8
double
double
double
seconds
44
52
60
sec/semic
2
sec/(semic.)
9
Beta 3rd order term
8
double
3
68
sec/(semic.)
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Logs summary
UTCB FORMAT:
Field #
Message ID = 17
Message Byte Count = 52
Field Type
Bytes
Format
char
Units
Offset
1
Sync
3
0
3
4
8
(header)
Checksum
Message ID
1
4
4
8
8
4
4
4
4
4
4
char
integer
integer
double
double
integer
integer
integer
integer
integer
integer
Message byte count
2
3
4
5
6
7
8
9
Polynomial constant term
seconds
12
20
28
32
36
40
44
48
Polynomial 1st order term
UTC data reference time
seconds/second
seconds
weeks
Week number UTC reference
Week number for leap sec effect time
Delta time due to leap sec
For use when leap sec on past
Day number for leap sec effect time
weeks
seconds
seconds
days
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Logs summary
BSLA/B Baseline Measurement
RTK
This log contains the most recent matched baseline representing the vector from the reference station receiver to
the remote station receiver. It is expressed in ECEF coordinates with corresponding uncertainties along each axis,
and a time tag. The estimated variance of the baseline in ECEF XYZ coordinates is the same as the XYZ position
variance.
It is recommended that you use the trigger ‘on changed’ which will log the selected data only when the data has
changed.
BSLA
Structure:
#sv
$BSLA week
∆x ∆y
seconds
∆z ∆x σ
#high
L1L2 #high
∆y σ
∆z σ soln status
posn type stn ID *xx
rtk status
[CR][LF]
Field #
Field type
Data Description
Example
1
$BSLA
week
Log header
$BSLA
2
3
4
5
GPS week number
872
seconds
#sv
GPS time into the week (in seconds)
174962.00
Number of matched satellites; may differ from the number in view.
8
7
#high
Number of matched satellites above RTK mask angle; observations from satellites
below mask are heavily de-weighted.
6
L1L2 # high
∆x
∆y
∆z
∆x σ
Number of matched satellites above RTK mask angle with both L1 and L2 available
ECEF X baseline component (remote stn. - reference stn.); in meters
ECEF Y baseline component (remote stn. - reference stn.); in meters
ECEF Z baseline component (remote stn. - reference stn.); in meters
Standard deviation of ∆x solution element; in meters
Standard deviation of ∆y solution element; in meters
Standard deviation of ∆z solution element; in meters
Solution status (see Table D-1)
7
7
-1.346
-3.114
-2.517
0.005
0.004
0.005
0
8
9
10
11
12
13
14
15
16
17
18
∆y σ
∆z σ
soln status
rtk status
posn type
stn ID
*xx
RTK status (see Tables D-3, D-4)
0
Position type (see Table D-2)
4
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Checksum
119
*36
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$BSLA,872,174962.00,8,7,7,-1.346,-3.114,
-2.517,0.005,0.004,0.005,0,0,4,119*36[CR][LF]
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Logs summary
BSLB
Format:
Message ID = 59
Message byte count = 100
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
0
(header)
Checksum
1
4
4
4
8
4
4
char
3
Message ID
integer
integer
integer
double
integer
integer
4
Message byte count
Week number
8
2
3
4
5
weeks
12
16
24
28
GPS time into the week
Number of matched satellites (00-12)
seconds
Number of matched satellites above RTK mask
angle
6
Number of matched satellites above RTK mask
angle with both L1 and L2 available
4
integer
32
7
ECEF X baseline
8
8
8
8
8
8
4
4
4
4
double
double
double
double
double
double
integer
integer
integer
integer
meters
meters
meters
meters
meters
meters
36
44
52
60
68
76
84
88
92
96
8
ECEF Y baseline
9
ECEF Z baseline
10
11
12
13
14
15
16
Standard deviation of X baseline
Standard deviation of Y baseline
Standard deviation of Z baseline
Solution status (see Table D-1)
RTK status (see Tables D-3, D-4)
Position type (see Table D-2)
Reference station identification (RTCM: 0 - 1023, or
RTCA: 266305 - 15179385)
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Logs summary
Table D-1 GPSCard Solution Status
Description
Value
0
1
2
3
Solution computed
Insufficient observations
No convergence
T
Singular A PA Matrix
4
5
6
7
Covariance trace exceeds maximum (trace > 1000 m)
Test distance exceeded (maximum of 3 rejections if distance > 10 km)
Not yet converged from cold start
Height or velocity limit exceeded. (In accordance with COCOM export
licensing restrictions)
Higher numbers are reserved for future use
Table D-2 Position Type
Type
Definition
0
1
2
3
4
5
No position
Single point position
Differential pseudorange position
RT-20 position
RT-2 position
WAAS position solution
Higher numbers are reserved for future use
Table D-3 RTK Status for Position Type 3 (RT-20)
Definition
Status
0
1
2
3
4
5
6
7
8
Floating ambiguity solution (converged)
Floating ambiguity solution (not yet converged)
Modeling reference phase
Insufficient observations
Variance exceeds limit
Residuals too big
Delta position too big
Negative variance
RTK position not computed
Higher numbers are reserved for future use
Table D-4 RTK Status for Position Type 4 (RT-2)
Definition
Status
0
1
2
3
4
5
6
7
8
9
10
Narrow lane solution
Wide lane derived solution
Floating ambiguity solution (converged)
Floating ambiguity solution (not yet converged)
Modeling reference phase
Insufficient observations
Variance exceeds limit
Residuals too big
Delta position too big
Negative variance
RTK position not computed
Higher numbers are reserved for future use
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Logs summary
CDSA/B Communication and Differential Decode Status
The GPSCard maintains a running count of a variety of status indicators of the data link. This log outputs a report
of those indicators.
Parity and framing errors will occur if poor transmission lines are encountered or if there is an incompatibility in
the data protocol. If errors occur, you may need to confirm the bit rate, number of data bits, number of stop bits and
parity of both the transmit and receiving ends. Overrun errors will occur if more characters are sent to the UART
than can be removed by the on-board microprocessor.
CDSA
Structure
$cdsa week
rx1 tx1
rtca rtcaa rtca
seconds xon1
csts1
parity1
overrun1
framing2
framing1
rx2 tx2
xon2
cts2
parity2 overrun2
rtcm
par
rtcma
fail
rtcm
good
dcsa
dsca
good
crc
fail
good
fail
dcsb dcsb
cmr
fail
cmr
good
res’d
*xx
[CR][LF]
fail
Field # Field type
good
Data Description
Example
$CDSA
787
1
2
3
4
$CDSA
week
Log header
GPS week number
seconds
xon1
GPS seconds into the week
500227
Flag to indicate that the com1 is using XON/XOFF handshaking protocol and port has received
an xoff and will wait for an xon before sending any more data.
0
5
cts1
Flag to indicate that com1 is using CTS/RTS handshake protocol and cts line port has been
asserted. The port will wait for the line to de-assert before sending any more data.
0
6
parity1
overrun1
framing1
rx1
The number of character parity errors from the UART of COM1
The number of UART buffer overrun errors of COM1
The number of character framing errors from the UART of COM1
The number of the characters received from COM1
The number of the characters sent out to COM1
0
0
0
0
9
0
7
8
9
10
11
tx1
xon2
Flag to indicate that COM2 is using XON/XOFF handshaking protocol and port has received an
xoff and will wait for an xon before sending any more data.
12
cts2
Flag to indicate that COM2 is using CTS/RTS handshake protocol and cts line port has been
asserted. The Port will wait for the line to de-assert before sending any more data.
0
13
14
15
16
17
18
19
parity2
overrun2
framing2
rx2
The number of character parity errors from the UART of COM2
The number of UART buffer overrun errors of COM2
The number of character framing errors from the UART of COM2
The number of characters received from COM2
The number of characters sent out to COM2
0
0
0
0
9
0
0
tx2
rtcacrc
rtcaafail
The number of RTCA CRC failures
The number of invalid ASCII $RTCA,....,*xx records indicating that the ASCII checksum “xx”
failed.
20
21
22
rtcagood
rtcmpar
rtcmafail
The number of RTCA records that pass error checking
The number of 30 bit RTCM parity failures
0
0
0
The number of invalid ASCII $RTCM,....,*xx records indicating that the ASCII checksum “xx”
failed.
23
24
rtcmgood
dcsafail
The number of RTCM records that pass error checking
DCSA is now obsolete.
0
0
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Logs summary
Field # Field type
Data Description
Example
25
26
27
28
29
30
31
32
dcsagood
dcsbfail
dcsbgood
cmrfail
DCSA is now obsolete.
DCSB is now obsolete.
DCSB is now obsolete.
0
0
0
The number of CMR messages which have failed error checking
The number of good CMR messages received
Reserved for future use
0
cmrgood
res’d
0
0
*xx
Checksum
*33
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$CDSA,787,500227,0,0,0,0,0,0,9,0,0,0,0,0,0,9,0,0,0,0,0,0,0,0,0,0,0,0,0*33[CR][LF]
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Logs summary
CDSB
Format:
Message ID = 39
Message byte count = 128
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
1
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
0
3
4
8
(header)
Checksum
char
Message ID
Message byte count
Week number
Time of week
Xon COM1
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
2
weeks
seconds
12
3
16
4
20
5
CTS COM1
24
6
Parity errors COM1
28
7
Overrun errors COM1
Framing error COM1
Bytes received in COM1
Bytes sent out COM1
Xon COM2
32
8
36
9
40
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
44
48
CTS COM2
52
Parity errors COM2
Overrun errors COM2
Framing error COM2
Bytes received in COM2
Bytes sent out COM2
RTCA CRC fails
56
60
64
68
72
76
RTCAA checksum fails
RTCA records passed
RTCM parity fails
RTCMA checksum fails
RTCM records passed
DCSA checksum
80
84
88
92
96
100
104
108
112
116
120
124
DCSA records passed
DCSB checksum fails
DCSB records passed
Reserved
Reserved
Reserved
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Logs summary
CLKA/B
Receiver Clock Offset Data
This record is used to monitor the state of the receiver time. Its value will depend on the CLOCKADJUST command.
If CLOCKADJUST is enabled, then the offset and drift times will approach zero. If not enabled, then the offset will
grow at the oscillator drift rate. Disabling CLOCKADJUST and monitoring the CLKA/B log will allow you to
determine the error in your GPSCard receiver reference oscillator as compared to the GPS satellite reference.
All logs report GPS time not corrected for local receiver clock error. To derive the closest GPS time one must subtract
the clock offset shown in the CLKA log (field 4) from GPS time reported.
The internal units of the new clock model’s three states (offset, drift and GM state) are meters, meters per second,
and meters. When scaled to time units for the output log, these become seconds, seconds per second, and seconds,
respectively. Note that the old units of the third clock state (drift rate) are seconds per second per second.
CLKA
Structure:
offset
*xx
$CLKA
week seconds
drift
SA G-M state offset std
drift std cm status
[CR][LF]
Field #
Field type
$CLKA
Data Description
Example
$CLKA
1
2
3
4
Log header
GPS week number
GPS seconds into the week
week
637
seconds
offset
511323.00
Receiver clock offset, in seconds. A positive offset implies that the
receiver clock is ahead of GPS Time. To derive GPS time, use the
-4.628358547E-003
following formula:
GPS time = receiver time - (offset)
5
6
drift
Receiver clock drift, in seconds per second. A positive drift implies that -2.239751396E-007
the receiver clock is running faster than GPS Time.
SA G-M state
This field contains the output value of the Gauss-Markov Selective
Availability clock dither estimator, in units of seconds. The value reflects
both the collective SA-induced short-term drift of the satellite clocks as
well asanyrangebiasdiscontinuitiesthatwouldnormallyaffectthe clock
model’s offset and drift states.
2.061788299E-006
7
8
9
offset std
drift std
Standard deviation of receiver clock offset, in seconds
Standard deviation of receiver drift, in seconds per second
5.369997167E-008
4.449097711E-009
0
cm status
Receiver Clock Model Status where 0 is valid and values from -20 to -1
imply that the model is in the process of stabilization
10
11
*xx
Checksum
*7F
[CR][LF]
Sentence terminator
[CR][LF]
Example
$CLKA,841,499296.00,9.521895494E-008,-2.69065747E-008,2.061788299E-006,
9.642598169E-008,8.685638908E-010,0*4F
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Logs summary
CLKB
Format:
Message ID = 02
Message byte count = 68
Field #
1
Field Type
Bytes
Format
char
Units
Offset
Sync
3
0
3
4
8
(header)
Checksum
1
4
4
4
8
8
8
8
8
8
4
char
Message ID
integer
integer
integer
double
double
double
double
double
double
integer
Message byte count
Week number
2
3
4
5
6
7
8
9
weeks
12
16
24
32
40
48
56
64
Seconds of week
Clock offset
seconds
seconds
Clock drift
seconds per second
seconds
SA Gauss-Markov state
StdDev clock offset
StdDev clock drift
Clock model status
seconds
seconds per second
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Logs summary
CLMA/B Receiver Clock Model
The CLMA and CLMB logs contain the current clock-model matrices of the GPSCard. These logs can be both
generated and received by a GPSCard.
NOTE: Only advanced users should seek to alter the clock model parameters of a GPSCard.
Throughout the following, these symbols are used:
B =
range bias (m)
BR = range bias rate (m/s)
SAB = Gauss-Markov process representing range bias error due to SA clock dither (m)
For further information, please refer to the documentation given for the clka/b log.
The standard clock model now used is as follows:
clock parameters array = [ B BR SAB]
covariance matrix =
σ2
σ σ
σ σ
B
BR
B
SAB
B
σ σ
σ2
σ σ
BR
B
BR
BR SAB
σ
SAB σ σSAB σ
σ2
B
BR
SAB
CLMA
Structure:
$CLMA
status
reject noise time
update
parameters covariance
*xx [CR][LF]
Field #
Field type
$CLMA
Data Description
Log header
Example
1
2
$CLMA
status
Status of clock model (0 = good;
-1 to -20 = bad)
0
3
4
reject
Number of rejected range bias
measurements (max. = 5)
0
noise time
GPS time of last estimate
(seconds)
- since Jan. 3, 1980 -
5.113140990E+010
5.113140990E+010
5
update
GPS time of last update
(seconds)
- since Jan. 3, 1980 -
6 - 8
parameters
covariance
Parameters array (1 x 3 = 3
elements)
5.810550069E+003, -1.07377180E+002, -1.41936974E+002
9 - 17
Covariance matrix (3x3 = 9
elements), listed left-to-right by
rows
9.744136534E+004, 1.676933050E+003, -8.98776739E+004,
1.676933050E+003, 4.750666170E+002, -7.06077622E+002,
-8.98776739E+004, -7.06077622E+002, 8.996728013E+004
18
19
*xx
Checksum
*00
[CR][LF]
Sentence terminator
[CR][LF]
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Logs summary
Example:
$CLMA,0,0,5.113140990E+010,5.113140990E+010,5.810550069E+003,
-1.07377180E+002,-1.41936974E+002,9.744136534E+004,
1.676933050E+003,-8.98776739E+004,1.676933050E+003,
4.750666170E+002,-7.06077622E+002,-8.98776739E+004,
-7.06077622E+002,8.996728013E+004*00[CR][LF]
CLMB
Format:
Message ID = 51
Message byte count = 132
Field #
Field Type
Bytes
Format
char
Units
Offset
0
1
Sync
3
(header)
Checksum
1
char
3
Message ID
4
integer
integer
integer
integer
double
double
double
double
4
Message byte count
4
bytes
8
2
Status of clock model (figure of quality)
Number of rejected observations
GPS time of last estimate
GPS time of last update
Parameters array (1x3 = 3 elements)
4
0 = good; -1 to -20 = bad
observations
seconds
12
16
20
28
36
60
3
4
4
8
5
8
seconds
6 - 8
9 - 17
3 x 8
[m
m/s
m]
2
2
2
Covariance matrix (3x3 = 9 elements), 9 x 8
listed left-to-right by rows
[ m
m /s
m
2
2 2
2
m /s m /s m /s
2
2
2
m
m /s m ]
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D
Logs summary
CMR Standard Logs
The Compact Measurement Record (CMR) Format, a standard communications protocol used in Real-Time
Kinematic (RTK) systems to transfer GPS carrier phase and code observations from a reference station to one or
more rover stations.
See Chapter 4 for more information on CMR standard logs.
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Logs summary
COM1A/B and COM2A/B Pass-Through Logs
There are two pass-through logs COM1A/B and COM2A/B, available on MiLLennium GPSCards.
The pass-through logging feature enables the GPSCard to redirect any ASCII or binary data that is input at a
specified port (COM1 or COM2) to any specified GPSCard port (COM1 or COM2). This capability, in conjunction with
the SEND command, can allow the GPSCard to perform bi-directional communications with other devices such as
a modem, terminal, or another GPSCard.
Please see Chapter 3 for more information.
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Logs summary
DOPA/B
Dilution of Precision
The dilution of precision data is calculated using the geometry of only those satellites that are currently being
tracked and used in the position solution by the GPSCard and updated once every 60 seconds or whenever a change
in the constellation occurs. Therefore, the total number of data fields output by the log is variable, depending on
the number of SVs tracking. Twelve is the maximum number of SV PRNs contained in the list.
NOTE: If a satellite is locked out using the LOCKOUT command, it will still be shown in the PRN list, but is
significantly deweighted in the DOP calculation.
DOPA
Structure:
$DOPA week seconds
gdop pdop htdop hdop tdop # sats
prn list
*xx
[CR][LF]
Field #
Field type
$DOPA
week
Data Description
Example
$DOPA
637
1
2
3
4
Log header
GPS week number
GPS seconds into the week
seconds
gdop
512473.00
Geometric dilution of precision - assumes 3-D position and receiver clock offset (all 2.9644
4 parameters) are unknown
5
pdop
Position dilution of precision - assumes 3-D position is unknown and receiver clock 2.5639
offset is known
6
7
8
htdop
hdop
tdop
Horizontal position and time dilution of precision.
Horizontal dilution of precision.
2.0200
1.3662
1.4880
Time dilution of precision - assumes 3-D position is known and only receiver clock
offset is unknown
9
# sats
prn list
Number of satellites used in position solution (0-12)
6
10...
PRN list of SV PRNs tracking (1-32), null field until first position solution available
18,6,11,2,16,
19
variable
variable
*xx
Checksum
*29
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$DOPA,637,512473.00,2.9644,2.5639,2.0200,1.3662,1.4880,6,18,6,11,2,16,19
*29[CR][LF]
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Logs summary
DOPB
Format:
Message ID = 07
Message byte count = 68+(sats*4)
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
1
4
4
4
8
8
8
8
8
8
4
4
0
3
4
8
(header)
Checksum
Message ID
Message byte count
Week number
Seconds of week
gdop
char
integer
integer
integer
double
double
double
double
double
double
integer
integer
2
weeks
seconds
12
16
24
32
40
48
56
64
68
3
4
5
pdop
6
htdop
7
hdop
8
tdop
9
Number of satellites used
1st PRN
10
11...
Next satellite PRN
Offset = 68 + (sats 4) where sats = 0 to (number of sats-1)
*
154
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Logs summary
ETSA/B
Extended Tracking Status
These logs provide channel tracking status information for each of the GPSCard parallel channels.
NOTE: This log is intended for status display only; since some of the data elements are not synchronized
together, they are not to be used for measurement data. Please use the RGEA/B/D, SATA/B, and
SVDA/B logs to obtain synchronized data for post processing analysis.
If both the L1 and L2 signals are being tracked for a given PRN, two entries with the same PRN will appear in the
tracking status logs. As shown in Table D-5 Receiver Self Test Status Codes these entries can be differentiated by
bit 19, which is set if there are multiple observables for a given PRN, and bit 20, which denotes whether the
observation is for L1 or L2. This is to aid in parsing the data.
ETSA
Structure:
sol status
# obs
$ETSA
week
seconds
prn ch-tr-status dopp C/No residual
:
locktime
psr reject code
dopp
residual
locktime
psr
prn ch-tr-status
C/No
reject code
*xx
[CR][LF]
Field #
Field type
Data Description
Example
$ETSA
850
1
2
3
$ETSA
Log header
GPS week number
week
seconds
GPS seconds into the week (receiver time, not corrected for clock
error, CLOCKADJUST enabled)
332087.00
4
5
6
7
sol status
# obs
Number of observations to follow
0
24
prn
Satellite PRN number (1-32) (channel 0)
7
ch-tr-status
Hexadecimal number indicating channel tracking status (See Table
00082E04
8
dopp
Instantaneous carrier Doppler frequency (Hz)
Carrier to noise density ratio (dB-Hz)
-613.5
9
C/No
54.682
27.617
12301.4
10
11
12
residual
locktime
psr
Residual from position filter (m)
Number of seconds of continuous tracking (no cycle slips)
Pseudorange measurement (m)
20257359.5
7
13
reject code
Indicates whether the range is valid (code = 0) or not (see Table D-
0
14-21
..
94-101
..
..
..
Next PRN #,ch-tr-status,dopp,C/No,residual,locktime,psr,reject code
..
Last PRN #,ch-tr-status,dopp,C/No,residual,locktime,psr,reject code
102
103
.
*xx
Checksum
*19
[CR][LF]
Sentence terminator
[CR][LF]
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Logs summary
Example (carriage returns have been added between observations for clarity):
$ETSA,850,332087.00,0,24,
7,00082E04,-613.5,54.682,27.617,12301.4,20257359.57,0,
7,00582E0B,-478.1,46.388,0.000,11892.0,20257351.96,13,
5,00082E14,3311.2,35.915,1.037,1224.4,24412632.47,0,
5,00582E1B,2580.4,39.563,0.000,1186.7,24412629.40,13,
9,00082E24,1183.1,53.294,-29.857,7283.8,21498303.67,0,
9,00582E2B,921.9,44.422,0.000,7250.2,21498297.13,13,
2,00082E34,-2405.2,50.824,-20.985,19223.6,22047005.47,0,
2,00582E3B,-1874.1,41.918,0.000,19186.7,22046999.44,13,
4,00082E44,3302.8,47.287,7.522,3648.1,22696783.36,0,
4,00582E4B,2573.6,37.341,0.000,3191.2,22696778.15,13,
14,00082E54,2132.7,41.786,-22.388,541.3,25117182.07,0,
14,00582E5B,1661.7,33.903,0.000,500.7,25117179.63,13,
26,00082E64,-3004.3,43.223,2.928,14536.2,25074382.19,0,
26,00582E6B,-2340.9,33.019,0.000,14491.7,25074378.01,13,
15,00082E74,-3037.7,43.669,0.508,12011.5,24104788.88,0,
15,00582E7B,-2367.0,34.765,0.000,11842.4,24104781.53,13,
24,00082E84,3814.0,37.081,7.511,95.7,25360032.49,0,
24,00582E8B,2972.0,24.148,0.000,5.2,25360030.13,13,
28,00082A90,-9800.9,0.000,0.000,0.0,0.00,9,
28,00382A90,-7637.0,0.000,0.000,0.0,0.00,9,
3,000822A0,-3328.3,0.000,0.000,0.0,0.00,9,
3,005828A0,-2593.5,0.000,0.000,0.0,0.00,9,
27,000822B0,-3851.7,0.000,0.000,0.0,0.00,9,
27,005828B0,-3001.7,0.000,0.000,0.0,0.00,9,*41[CR][LF]
ETSB
Format: Message ID = 48 Message byte count = 32 + (n x 52) where n is number of observations
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
4
4
0
(header)
Checksum
Message ID
char
3
integer
integer
integer
double
integer
integer
4
Message byte count
8
2
3
4
5
Week number
weeks
12
16
24
28
Time of week
seconds
Number of observations
6
7
PRN number (first observation)
4
4
integer
integer
32
36
8
9
Doppler
8
8
double
double
Hz
40
48
C/N
0
dB-Hz
10
Residual
8
8
8
4
double
double
double
integer
meters
seconds
meters
56
64
72
80
11
Locktime
12
Pseudorange
13
14 ...
Offset = 32 + (#obs x 52) where #obs varies from 0 - 23
156
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Logs summary
FRMA/B Framed Raw Navigation Data
This message contains the raw framed navigation data. An individual message is sent for each PRN being tracked.
The message is updated with each new frame, therefore it is best to log the data with the ‘onnew’ trigger activated.
FRMA
Structure:
$FRMA week
seconds
prn cstatus
# of bits framed raw data
*xx
[CR][LF]
Field type
$FRMA
Field #
Data Description
Example
$FRMA
1
2
3
4
5
6
Log header
week
GPS week number
845
seconds
prn
GPS seconds into the week
238623.412
PRN of satellite from which data originated
120
cstatus
# of bits
80811F14
250
Number of bits transmitted in the message. 250 for
WAAS, 300 for GPS and 85 for GLONASS.
7
framed raw data
One field of raw framed navigation data.
9AFE5354656C2053796E636
8726F6E69636974792020202
020202020B0029E40*3F
8
9
*xx
Checksum
*42
[CR][LF]
Sentence terminator
[CR][LF]
FRMB
Format:
Message ID = 54
Message byte count = variable
Field #
1
Data
Bytes
Format
Units
Offset
Sync
3
1
4
4
4
8
4
4
4
char
0
(header)
Checksum
char
3
Message ID
Message byte count
Week number
Seconds of week
PRN number
integer
integer
integer
double
integer
integer
integer
4
bytes
8
2
3
4
5
6
weeks
seconds
1-999
n/a
12
16
24
28
32
Number of Bits
250 for WAAS
300 for GPS
85 for GLONASS
7
Data Sub-frame
variable
char
N/A
36
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Logs summary
GGAB
Global Position System Fix Data (Binary Format Only)
Time, position and fix-related data of the GPS receiver. This binary log is a replica of the NMEA GPGGA ASCII log
expressed in binary format with NovAtel header added.
Format:
Message ID = 27
Message byte count = 80
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
1
4
4
8
8
0
(header)
Checksum
char
3
Message ID
integer
integer
double
double
4
Message byte count
UTC time of position
8
2
3
hhmmss.ss
degrees
12
20
Latitude (DDmm.mm)
(+ is North, - is South)
4
5
Longitude (DDDmm.mm)
(+ is East, - is West)
8
4
double
integer
degrees
28
36
Fix status
0
1
2
4
5
=
=
=
=
=
fix not available or invalid
GPS fix
Differential GPS fix
RTK fixed ambiguity solution
RTK floating ambiguity solution
2
9
=
WAAS
6
Number of satellites in use. May be different to the number in view
Horizontal dilution of precision
4
8
8
8
8
integer
double
double
double
double
40
44
52
60
68
7
8
Antenna altitude above/below mean-sea-level (geoid)
meters
meters
seconds
9
1
10
Age of Differential GPS data
11
Differential reference station ID, 0000-1023
4
integer
76
Note:
1
2
The maximum age reported here is limited to 99 seconds.
An indicator of 9 has been temporarily set for WAAS. Then NMEA standard for WAAS has not been decided yet.
158
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Logs summary
GPALM
Almanac Data
This log outputs raw almanac data for each satellite PRN contained in the broadcast message. A separate record is
logged for each PRN, up to a maximum of 32 records. Following a GPSCard reboot, no records will be output until
new broadcast message data is received from a satellite. It takes a minimum of 12.5 minutes to collect a complete
almanac following GPSCard boot-up. (The almanac reported here has no relationship to the NovAtel $ALMA
almanac injection command. Following a cold start, the log will output null fields until a new almanac is collected
from a satellite.)
Structure:
# msg
$GPALM
msg # PRN
incl angle
GPS wk SV hlth ecc
alm ref time
omega
omegadot
*xx
rt axis
long asc node
a
M
[CR][LF]
f1
o
Exam-
ple
Field
Structure
Field Description
Symbol
1
2
3
4
5
$GPALM
Log header
$GPALM
17
# msg
msg #
PRN
Total number of messages logged
Current message number
x.x
x.x
xx
17
Satellite PRN number, 01 to 32
28
GPS wk
1
2
3
3
3
x.x
653
GPS reference week number
SV health, bits 17-24 of each almanac page
e, eccentricity
6
7
8
9
SV hlth
ecc
hh
00
hhhh
hh
3EAF
87
alm ref time
incl angle
toa, almanac reference time
hhhh
OD68
(sigma) , inclination angle
i
10
11
12
13
14
15
16
omegadot
rt axis
3
3
3
3
3
3
3
hhhh
FD30
OMEGADOT, rate of right ascension
hhhhhh
hhhhhh
hhhhhh
hhhhhh
hhh
A10CAB
6EE732
525880
6DC5A8
009
1/2
(A) , root of semi-major axis
omega
omega, argument of perigee
long asc node
o
(OMEGA) ,longitude of ascension node
M
o
Mo, mean anomaly
af0, clock parameter
a
f0
a
hhh
005
f1
af1, clock parameter
Checksum
17
18
*xx
*hh
*37
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPALM,17,17,28,653,00,3EAF,87,0D68,FD30,A10CAB,6EE732,525880,6DC5A8,009,
005*37[CR][LF]
1
Variable length integer, 4-digits maximum from (2) most significant binary bits of Subframe 1, Word 3
reference Table 20-I, ICD-GPS-200, Rev. B, and (8) least significant bits from subframe 5, page 25, word 3
reference Table 20-I, ICD-GPS-200, Rev. B, paragraph 20.3.3.5.1.7
2
3
Reference paragraph 20.3.3.5.1.3, Table 20-VII and Table 20-VIII, ICD-GPS-200, Rev. B
Reference Table 20-VI, ICD-GPS-200, Rev. B for scaling factors and units.
To obtain copies of ICD-GPS- 200, see Appendix F, Standards and References, Page 233, for address information.
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Logs summary
GPGGA
Global Position System Fix Data
Time, position and fix-related data of the GPS receiver. The information contained in this log is also available in
the NovAtel GGAB log in binary format. This log will output all null data fields until the GPSCard has achieved
first fix.
Structure:
$GPGGA
alt
utc
lat
lat dir
lon lon dir GPS qual # sats hdop
*xx [CR][LF]
Symbol
units null null age stn ID
Field
Structure
$GPGGA
utc
Field Description
Example
$GPGGA
220147.50
5106.7194489
N
1
2
3
4
5
6
7
Log header
UTC time of position (hours/minutes/seconds/ decimal seconds)
Latitude (DDmm.mm)
hhmmss.ss
lat
llll.ll
lat dir
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
a
lon
yyyyy.yy
11402.3589020
W
lon dir
GPS qual
Longitude direction (E = East, W = West)
a
x
GPS Quality indicator
1
0 =
1 =
2 =
4 =
5 =
fix not available or invalid
GPS fix
Differential GPS fix
RTK fixed ambiguity solution
RTK floating ambiguity solution
2
9 =
WAAS
8
# sats
hdop
alt
Number of satellites in use (00-12). May be different to the number in view xx
08
9
Horizontal dilution of precision
x.x
x.x
M
0.9
10
11
12
13
14
Antenna altitude above/below mean sea level (geoid)
Units of antenna altitude (M = meters)
(This field not available on GPSCards)
(This field not available on GPSCards)
1080.406
units
null
M
,,
null
,,
1
age
xx
,,
Age of Differential GPS data (in seconds)
Differential reference station ID, 0000-1023
Checksum
15
16
17
stn ID
*xx
xxxx
*hh
,,
*48
[CR][LF]
Sentence terminator
[CR][LF]
1
2
The maximum age reported here is limited to 99 seconds.
An indicator of 9 has been temporarily set for WAAS. Then NMEA standard for WAAS has not been decided yet.
Example:
$GPGGA,220147.50,5106.7194489,N,11402.3589020,W,1,08,0.9,1080.406,M,,,,
*48[CR][LF]
160
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Logs summary
GPGLL
Geographic Position
Latitude and longitude of present vessel position, time of position fix, and status. This log will output all null data
fields until the GPSCard has achieved first fix.
Structure:
$GPGLL lat lat dir lon lon dir utc data status *xx [CR][LF]
Field
Structure
$GPGLL
lat
Field Description
Symbol
llll.ll
Example
$GPGLL
1
2
3
4
5
6
Log header
Latitude (DDmm.mm)
5106.7198674
N
lat dir
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
a
lon
yyyyy.yy
a
11402.3587526
W
lon dir
utc
Longitude direction (E = East, W = West)
UTC time of position (hours/minutes/seconds/decimal
seconds)
hhmmss.ss
220152.50
7
8
9
data status
*xx
Data status: A = Data valid, V = Data invalid
Checksum
A
A
*hh
*1B
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPGLL,5106.7198674,N,11402.3587526,W,220152.50,A*1B[CR][LF]
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Logs summary
GPGRS GPS Range Residuals for Each Satellite
Range residuals can be computed in two ways, and this log reports those residuals. Under mode 0, residuals output
in this log are used to update the position solution output in the GPGGA message. Under mode 1, the residuals are
re-computed after the position solution in the GPGGA message is computed. The GPSCard computes range residuals
in mode 1. An integrity process using GPGRS would also require GPGGA (for position fix data), GPGSA (for DOP
figures), and GPGSV (for PRN numbers) for comparative purposes.
Structure:
$GPGRS
utc mode
res res
res res res res res res res res
res res
*xx [CR][LF]
Field Structure
Field Description
Symbol
Example
$GPGRS
UTC time of position (hours/minutes/seconds/ decimal seconds) hhmmss.ss 192911.0
1
2
3
$GPGRS
utc
Log header
mode
Mode 0 =residuals were used to calculate the position given in
the matching GGA line (apriori) (not used by GPSCard)
Mode 1 =residuals were recomputed after the GGA position was
computed (preferred mode)
x
1
4 - 15 res
Range residuals for satellites used in the navigation solution.
Order matches order of PRN numbers in GPGSA.
x.x,x.x,.....
*hh
-13.8,-1.9,11.4,-33.6,0.9,
6.9,-12.6,0.3,0.6, -22.3
16
17
*xx
Checksum
*65
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPGRS,192911.0,1,-13.8,-1.9,11.4,-33.6,0.9,6.9,-12.6,0.3,0.6,-22.3,,
*65[CR][LF]
NOTE: If the range residual exceeds ± 99.9, then the decimal part will be dropped. Maximum value for this
field is ± 999. The sign of the range residual is determined by the order of parameters used in the
calculation as follows:
range residual = calculated range - measured range
162
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Logs summary
GPGSA
GPS DOP and Active Satellites
GPS receiver operating mode, satellites used for navigation and DOP values.
Structure:
$GPGSA mode MA
prn
pdop hdop
Field Structure
mode 123
prn prn
vdop *xx
prn
prn prn prn prn prn prn prn prn
[CR][LF]
Field Description
Symbol
Example
$GPGSA
M
1
$GPGSA
mode MA
Log header
2
A = Automatic 2D/3D (not used by GPSCard) M = Manual, forced to
operate in 2D or 3D
M
x
3
mode 123
prn
Mode: 1 = Fix not available; 2 = 2D; 3 = 3D
3
4 - 15
PRN numbers of satellites used in solution (null for unused fields), total xx,xx,.....
of 12 fields
18,03,13,25,16,
24,12,20,,,,
16
17
18
19
20
pdop
hdop
vdop
*xx
Position dilution of precision
Horizontal position and time dilution of precision
Vertical dilution of precision
Checksum
x.x
x.x
x.x
*hh
1.5
0.9
1.2
*3F
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPGSA,M,3,18,03,13,25,16,24,12,20,,,,,1.5,0.9,1.2*3F[CR][LF]
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Logs summary
GPGST
Pseudorange Measurement Noise Statistics
Pseudorange measurement noise statistics are translated in the position domain in order to give statistical measures
of the quality of the position solution.
Structure:
$GPGST utc rms smjr std smnr std
lat std
lon std
alt std *xx [CR][LF]
orient
Field
Structure
Field Description
Symbol
Example
1
2
3
$GPGST
Log header
$GPGST
utc
UTC time of position (hours/minutes/seconds/ decimal seconds)
hhmmss.ss 192911.0
rms
RMS value of the standard deviation of the range inputs to the
navigation process. Range inputs include pseudoranges and DGPS
corrections.
x.x
28.7
4
smjr std
smnr std
orient
Standard deviation of semi-major axis of error ellipse (meters)
Standard deviation of semi-minor axis of error ellipse (meters)
x.x
x.x
21.6
12.0
20.4
20.7
13.6
11.9
*51
5
6
Orientation of semi-major axis of error ellipse (degrees from true north) x.x
7
lat std
lon std
alt std
*xx
Standard deviation of latitude error (meters)
Standard deviation of longitude error (meters)
Standard deviation of altitude error (meters)
Checksum
x.x
x.x
x.x
*hh
8
9
10
11
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPGST,192911.0,28.7,21.6,12.0,20.4,20.7,13.6,11.9*51[CR][LF]
164
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Logs summary
GPGSV
GPS Satellites in View
Number of SVs in view, PRN numbers, elevation, azimuth and SNR value. Four satellites maximum per message.
When required, additional satellite data sent in second or third message. Total number of messages being
transmitted and the current message being transmitted are indicated in the first two fields.
NOTE 1: Satellite information may require the transmission of multiple messages. The first field specifies the
total number of messages, minimum value 1. The second field identifies the order of this message
(message number), minimum value 1.
NOTE 2: A variable number of ’PRN-Elevation-Azimuth-SNR’sets are allowed up to a maximum of four sets per
message. Null fields are not required for unused sets when less than four sets are transmitted.
NOTE 3: GPGSV logs will not output until time of first fix.
Structure:
$GPGSV
# msg msg # # sats
prn elev azimuth SNR
:
prn elev azimuth SNR
*xx [CR][LF]
Field
Structure
$GPGSV
Field Description
Symbol
Example
1
2
3
4
5
6
7
8
Log header
$GPGSV
# msg
msg #
# sats
prn
Total number of messages, 1 to 3
Message number, 1 to 3
x
3
x
1
Total number of satellites in view
Satellite PRN number
xx
xx
xx
09
03
51
140
42
elev
Elevation, degrees, 90¡ maximum
Azimuth, degrees True, 000 to 359
azimuth
SNR
xxx
xx
SNR (C/N ) 00-99 dB, null when not tracking
0
...
...
...
...
...
...
Next satellite PRN number, elev, azimuth, SNR,
...
Last satellite PRN number, elev, azimuth, SNr,
variable
variable
*xx
Checksum
*hh
*72
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPGSV,3,1,09,03,51,140,42,16,02,056,40,17,78,080,42,21,25,234,00*72[CR][LF]
$GPGSV,3,2,09,22,19,260,00,23,59,226,00,26,45,084,39,27,07,017,39*78[CR][LF]
$GPGSV,3,3,09,28,29,311,44*42[CR][LF]
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Logs summary
GPRMB
Navigation Information
Navigation data from present position to a destination waypoint. The destination is set active by the GPSCard
SETNAV command. If SETNAV has been set, a command to log either GPRMB or GPRMC will cause both logs to output
data.
Structure:
$GPRMB
data status
xtrack
dir origin ID
lat dir dest lon
vel arr status
dest ID dest lat
lon dir
bearing
range
*xx [CR][LF]
Field
Structure
$GPRMB
data status
xtrack
Field Description
Symbol Example
1
2
3
4
5
6
7
Log header
Data status: A = data valid; V = navigation receiver warning
$GPRMB
A
V
x.x
a
0.011
L
Cross track error
1
2
3
3
3
dir
Direction to steer to get back on track (L/R)
Origin waypoint ID
origin ID
dest ID
c--c
c--c
llll.ll
START
END
Destination waypoint ID
dest lat
5106.7074
000
Destination waypoint latitude (DDmm.mm
8
lat dir
a
N
Latitude direction (N = North, S = South)
Destination waypoint longitude (DDDmm.mm)
Longitude direction (E = East, W = West)
Range to destination, nautical miles
Bearing to destination, degrees True
Destination closing velocity, knots
3
3
3
4
9
dest lon
lon dir
range
bearing
vel
yyyyy.yy
11402.349
E
10
11
12
13
14
a
x.x
x.x
x.x
A
0.0127611
153.093
0.3591502
V
arr status
Arrival status: A = perpendicular passed
V = destination not reached or passed
15
16
*xx
Checksum
*hh
*13
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPRMB,V,0.011,L,START,END,5106.7074000,N,11402.3490000,W,0.0127611,153093,
0.3591502,V*13[CR][LF]
1
2
- If cross track error exceeds 9.99 NM, display 9.99
- Represents track error from intended course
- one nautical mile = 1,852 meters
Direction to steer is based on the sign of the crosstrack error,
i.e., L = xtrack error (+); R = xtrack error (–)
3
4
Fields 5, 6, 7, 8, 9, and 10 are tagged from the GPSCard SETNAV command.
If range to destination exceeds 999.9 NM, display 999.9
166
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Logs summary
GPRMC
GPS Specific Information
Time, date, position, track made good and speed data provided by the GPS navigation receiver. RMC and RMB are
the recommended minimum navigation data to be provided by a GPS receiver. This log will output all null data
fields until the GPSCard has achieved first fix.
Structure:
$GPRMC utc pos status lat
lat dir
lon
lon dir speed Kn track true date
mag var
var dir
*xx [CR][LF]
Field Description
Log header
Field
Structure
Symbol
Example
$GPRMC
1
2
3
$GPRMC
utc
UTC of position
hhmmss.ss
A
220216.50
A
pos status
Position status: A = data valid
V = data invalid
4
lat
Latitude (DDmm.mm)
llll.ll
a
5106.7187663
N
5
lat dir
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
6
lon
yyyyy.yy
a
11402.3581636
W
7
lon dir
speed Kn
track true
date
Longitude direction (E = East, W = West)
Speed over ground, knots
8
x.x
0.3886308
130.632
150792
0.000
9
Track made good, degrees True
Date: dd/mm/yy
x.x
10
11
xxxxxx
x.x
2
mag var
Magnetic variation, degrees
1
12
var dir
a
E
Magnetic variation direction E/W
13
14
*xx
Checksum
*hh
*4B
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPRMC,220216.50,A,5106.7187663,N,11402.3581636,W,0.3886308,130.632,150792,
0.000,E*4B[CR][LF]
1
Easterly variation (E) subtracts from True course
Westerly variation (W) adds to True course
2 Note that this field is the actual magnetic variation East or West and is the inverse sign of the value entered into
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Logs summary
GPVTG
Track Made Good And Ground Speed
The track made good and speed relative to the ground.
Structure:
$GPVTG track true T track mag
M speed Km
N
speed km
Structure
K *xx
[CR][LF]
Field Description
Field
Symbol
Example
$GPVTG
24.168
T
1
$GPVTG
track true
T
Log header
2
3
4
Track made good, degrees True
True track indicator
x.x
T
track mag
Track made good, degrees Magnetic;
x.x
24.168
Track mag = Track true + (MAGVAR correction)
5
M
Magnetic track indicator
Speed over ground, knots
Nautical speed indicator (N = Knots)
Speed, kilometers/hour
Speed indicator (K = km/hr)
Checksum
M
M
6
speed Kn
N
x.x
N
0.4220347
N
7
8
speed Km
K
x.x
K
0.781608
K
9
10
11
*xx
*hh
*7A
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPVTG,24.168,T,24.168,M,0.4220347,N,0.781608,K*7A[CR][LF]
168
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Logs summary
GPZDA
UTC Time and Date
This log will output all null data fields until the GPSCard has achieved first fix.
Structure:
$GPZDA utc day month
NULL NULL *xx [CR][LF]
year
Field
Structure
$GPZDA
utc
Field Description
Symbol
Example
1
2
3
4
5
6
7
Log header
UTC time
$GPZDA
hhmmss.ss
220238.00
day
Day, 01 to 31
Month, 01 to 12
Year
xx
15
07
1992
, ,
month
year
xx
xxxx
xx
null
Local zone description - not available
1
null
xx
, ,
Local zone minutes description - not available
Checksum
8
9
*xx
*hh
*6F
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPZDA,220238.00,15,07,1992,00,00*6F[CR][LF]
Local time zones are not supported by the GPSCard. Fields 6 and 7 will always be null.
1
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Logs summary
GPZTG
UTC & Time to Destination Waypoint
This log reports time to destination waypoint. Waypoint is set using the GPSCard SETNAV command. If destination
waypoint has not been set with SETNAV, time-to-go and destination waypoint ID will be null. This log will output
all null data fields until the GPSCard has achieved first fix.
Structure:
$GPZTG utc time dest ID *xx [CR][LF]
Field
Structure
$GPZTG
Field Description
Log header
UTC of position
Symbol
Example
$GPZTG
220245.00
994639.00
END
1
2
3
4
5
6
utc
hhmmss.ss
time
Time to go (995959.00 maximum reported) hhmmss.ss
dest ID
*xx
Destination waypoint ID
Checksum
c--c
*hh
*36
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$GPZTG,220245.00,994639.00,END*36[CR][LF]
170
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Logs summary
MKPA/B
Mark Position
This log contains the estimated position of the antenna at detected mark impulse. It uses the last valid position and
velocities to extrapolate the position at time of mark. Refer to the GPSCard Installation and Operating Manual
Appendix for Mark Input pulse specifications. The latched time of mark impulse is in GPS weeks and seconds into
the week. The resolution of the latched time is 49 ns.
MKPA
Structure:
$MKPA week
seconds
lat lon hgt
undulation
datum ID
lat std lon std
hgt std
sol status *xx
[CR][LF]
Field #
Field type
$MKPA
Data Description
Example
1
2
3
Log header
GPS week number
$MKPA
653
week
seconds
GPSsecondsintotheweekmeasuredfromthereceiver clock, coincident withthe 338214.773382
time of electrical closure on the Mark Input port.
376
4
5
lat
Latitude of position in current datum, in degrees/decimal degrees
(DD.dddddddd), where a negative sign implies South latitude
51.11227014
lon
Longitude of position in current datum, in degrees/decimal degrees
(DDD.dddddddd), where a negative sign implies West longitude
-114.03907552
6
hgt
Height of position in current datum, in meters with respect to MSL
Standard deviation of latitude solution element, in meters
Standard deviation of longitude solution element, in meters
Standard deviation of height solution element, in meters
Solution status as listed in Table D-1
1003.799
-16.199
61
7
undulation
datum ID
lat std
8
9
7.793
3.223
34.509
0
10
11
12
13
14
lon std
hgt std
sol status
*xx
Checksum
*3C
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$MKPA,653,338214.773382376,51.11227014,-114.03907552,1003.799,-16.199,61,
7.793,3.223,34.509,0*3C[CR][LF]
MKPB
Format: Message ID = 05 Message byte count = 88
Field # Data Bytes Format
char
Units
Offset
1
Sync
3
0
3
4
8
(header)
Checksum
1
4
4
4
8
8
8
8
8
4
8
8
8
4
char
Message ID
integer
integer
integer
double
double
double
double
double
integer
double
double
double
integer
Message byte count
Week number
Seconds of week
Latitude
2
weeks
12
16
3
seconds
4
degrees (+ is North, - is South) 24
5
Longitude
degrees (+ is East, - is West)
meters with respect to MSL
meters
32
40
48
56
60
68
76
84
6
Height
7
Undulation
8
Datum ID
9
StdDev of latitude
StdDev of longitude
StdDev of height
Solution status
meters
meters
meters
10
11
12
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Logs summary
MKTA/B
Time of Mark Input
This log contains the time of the detected Mark Input pulse leading edge as detected at the Mark Input I/O port.
The resolution of this measurement is 49ns. Refer to the GPSCard Installation and Operating Manual Appendix
for the Mark Input pulse specifications.
MKTA
Structure:
$MKTA week seconds
offset
*xx
offset std
[CR][LF]
utc offset
cm status
Field #
Field type
Data Description
Example
$MKTA
1
$MKTA
week
Log header
2
3
GPS week number
653
seconds
Seconds into the week as measured from the receiver clock, coincident with the
time of electrical closure on the Mark Input port.
338214.773382376
4
offset
Receiver clock offset, in seconds. A positive offset implies that the receiver clock 0.000504070
is ahead of GPS Time. To derive GPS time, use the following formula:
GPS time = receiver time - (offset)
5
6
offset std
utc offset
Standard deviation of receiver clock offset, in seconds
0.000000013
-8.000000000
This field represents the offset of GPS time from UTC time, computed using
almanac parameters. To reconstruct UTC time, algebraically subtract this
correction from field 3 above (GPS seconds).
UTC time = GPS time - (utc offset)
7
cm status
Receiver Clock Model Status where 0 is valid and values from -20 to -1 imply that
the model is in the process of stabilization
0
8
9
*xx
Checksum
*05
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$MKTA,653,338214.773382376,0.000504070,0.000000013,-8.000000000,0 *05[CR][LF]
MKTB
Format:
Message ID = 04
Message byte count = 52
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
8
8
8
4
0
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
double
double
double
integer
4
Message byte count
Week number
Seconds of week
Clock offset
8
2
3
4
5
6
7
weeks
12
16
24
32
40
48
seconds
seconds
seconds
seconds
StdDev clock offset
UTC offset
Clock model status
172
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Logs summary
NAVA/B
Waypoint Navigation Data
This log reports the status of your waypoint navigation progress. It is used in conjunction with the SETNAV
command.
REMEMBER: The SETNAV command must be enabled before valid data will be reported from this log.
NAVA
Structure:
$NAVA week
seconds distance
bearing along track xtrack etaw
nav status sol status
etas
*xx [CR][LF]
Field #
Field type
Data Description
Example
$NAVA
1
2
3
4
$NAVA
week
Log header
GPS week number
GPS seconds into the week
640
seconds
distance
333115.00
6399.6305
Straight line horizontal distance from current position to the destination waypoint, in meters
becomes negative on passing the waypoint.
5
6
bearing
Direction from the current position to the destination waypoint in degrees with respect to True 88.017
North (or Magnetic if corrected for magnetic variation by MAGVAR command)
along track
Horizontal track distance from the current position to the closest point on the waypoint arrival 6396.9734
perpendicular; expressed in meters. This value is positive when approaching the waypoint
and becomes negative on passing the waypoint.
7
xtrack
The horizontal distance (perpendicular track-error) from the vessel’s present position to the
closest point on the great circle line that joins the FROM and TO waypoints. If a "track offset"
has been entered in the SETNAV command, xtrack will be the perpendicular error from the
"offset track". Xtrack is expressed in meters. Positive values indicate the current position is
right of the Track, while negative offset values indicate left.
184.3929
8
9
etaw
etas
Estimated GPS week number at time of arrival at the "TO" waypoint along-track arrival
perpendicular based on current position and speed, in units of GPS weeks. If the receiving
antenna is moving at a speed of less than 0.1 m/sec in the direction of the destination, the
value in this field will be"9999".
657
Estimated GPS seconds into week at time of arrival at destination waypoint along-track arrival 51514.000
perpendicular, based on current position and speed, in units of GPS seconds into the week.
If the receiving antenna is moving at a speed of less than 0.1 m/sec in the direction of the
destination, the value in this field will be"0.000".
10
11
12
13
nav status
sol status
*xx
Navigation data status, where 0 = good, 1 = no velocity, and 2 = bad navigation calculation
0
Checksum
1
*11
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$NAVA,640,333115.00,6399.6305,88.017,6396.9734,184.3929,657,51514.000,0,1
*11[CR][LF]
NOTE: All distances and angles are calculated using Vincenty’s long line geodetic equations that operate on the
currently selected user datum.
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Logs summary
NAVB
Format:
Message ID = 08
Message byte count = 76
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
8
8
8
8
4
8
4
0
3
4
8
(header)
Checksum
char
Message ID
Message byte count
Week number
Seconds of week
Distance
integer
integer
2
3
4
5
6
7
8
9
10
integer
double
double
double
double
double
integer
double
integer
weeks
12
16
24
32
40
48
56
60
68
seconds
meters
degrees
meters
meters
weeks
Bearing
Along track
Xtrack
ETA week
ETA seconds
seconds
NAV status where
0 = good
1 = no velocity
2 = bad navigation
11
Solution status
4
integer
72
174
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Logs summary
Figure D-1 Example of Navigation Parameters
A = FROM lat-lon
B = TO lat-lon
AB = Great circle line drawn between FROM A lat-lon and TO B lat-lon
AC = Track offset from A to C
BD = Track offset from B to D
CD = Offset track to steer (parallel to AB)
F = Current GPS position
FD = Current distance and bearing from F to D
E = Xtrack perpendicular reference point
EF = Xtrack error from E to F (perpendicular to CD)
FG = Along track from F to G (perpendicular to BD)
AB - True bearing = 70°
AB - Magnetic bearing = True + (MAGVAR correction)
= 70° + (-20)
= 50°
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Logs summary
PAVA/B
Position Averaging Status
These logs are meant to be used in conjunction with the POSAVE command. If the POSAVE command has not been
issued, all fields in the PAVA/B logs except week and seconds will be zero. However, when position averaging is
underway, the various fields contain the parameters being used in the position averaging process. The log trigger
ONCHANGED is recommended, but ONTIME can also be used.
NOTE: All quantities are referenced to the WGS84 ellipsoid, regardless of the use of the DATUM or USERDATUM
commands, except for the height parameter (field 6). The relation between the geoid and the WGS84
ellipsoid is the geoidal undulation, and can be obtained from the POSA/B logs.
PAVA
Structure :
$PAVA week seconds lat
lng
hgt
sdlat
sdlng
sdhgt time samples *xx
[CR][LF]
Field #
Field type
$PAVA
week
Data Description
Example
$PAVA
1
Log header
2
GPS week number
846
3
seconds
lat
GPS seconds into the week
145872.00
51.11381167
-114.04356455
1068.100
26.2
4
Average WGS84 latitude (degrees)
Average WGS84 longitude (degrees)
Average height above sea level, or geoid (m)
Estimated standard deviation of the average latitude (m)
5
lng
6
hgt
7
sdlat
8
sdlng
sdhgt
time
Estimated standard deviation of the average longitude (m) 12.1
9
Estimated standard deviation of the average height (m)
Elapsed time of averaging (s)
Number of samples in the average
Checksum
54.9
7
10
11
12
13
samples
*xx
1
*0C
[CR][LF]
[CR][LF]
Sentence terminator
Example:
$PAVA,846,145872.00,51.11381167,-114.04356455,1068.100,26.2,12.1,54.9,7,1*0C [CR][LF]
176
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Logs summary
PAVB
Format:
Message ID = 50
Message byte count = 80
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
8
8
8
8
0
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
double
double
double
double
4
Message byte count
GPS week number
8
2
3
4
5
6
7
weeks
12
16
24
32
40
48
GPS seconds into the week
Average WGS84 latitude
Average WGS84 longitude
Average height above sea level
seconds
degrees
degrees
meters
Estimated standard deviation of the
average latitude
meters
8
9
Estimated standard deviation of the
average longitude
8
8
double
double
meters
meters
seconds
56
64
Estimated standard deviation of the
average height
10
11
Elapsed time of averaging
4
4
integer
integer
72
76
Number of samples in the average
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Logs summary
POSA/B
Computed Position
This log will contain the last valid position and time calculated referenced to the GPSAntenna phase centre. The
position is in geographic coordinates in degrees based on your specified datum (default is WGS84). The height is
referenced to mean sea level. The receiver time is in GPS weeks and seconds into the week. The estimated standard
deviations of the solution and current filter status are also included. See also Section A.3.2 Pseudorange
POSA
Structure:
$POSA
week seconds lat lon hgt undulation
datum ID
lat std lon std hgt std sol status *xx
[CR][LF]
Field #
Type
$POSA
week
seconds
lat
Data Description
Example
$POSA
1
2
3
4
5
6
Log header
GPS week number
GPS seconds into the week
637
511251.00
51.11161847
Latitude of position in current datum, in degrees (DD.dddddddd). A - implies South latitude
lon
Longitude of position in current datum, in degrees (DDD.dddddddd). A + implies West longitude -114.03922149
hgt
Heightof position in currentdatum, in meterswithrespect tomean sealevel(see FigureD-2, Page 1072.436
7
undulation Geoidal separation, in meters, where + is above spheroid and - is below spheroid (see Figure C- -16.198
8
datum ID
lat std
61
9
Standard deviation of latitude solution element, in meters
Standard deviation of longitude solution element, in meters
Standard deviation of height solution element, in meters
26.636
6.758
78.459
0
10
lon std
hgt std
11
12
sol status Solution status as listed in Table D-1
13
*xx
Checksum
*12
14
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$POSA,637,511251.00,51.11161847,-114.03922149,1072.436,-16.198,61,26.636,
6.758,78.459,0*12[CR][LF]
POSB
Format:
Message ID = 01 Message byte count = 88
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
1
4
4
4
8
8
8
8
8
4
8
8
8
4
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
integer
double
double
double
double
double
integer
double
double
double
integer
Message byte count
Week number
Seconds of week
Latitude
2
weeks
12
16
3
seconds
4
degrees (+ is North, - is South) 24
5
Longitude
degrees (+ is East, - is West)
meters with respect to MSL
meters
32
40
48
56
60
68
76
84
6
Height
7
Undulation
8
Datum ID
9
StdDev of latitude
StdDev of longitude
StdDev of height
Solution status
meters
meters
meters
10
11
12
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Logs summary
PRTKA/B
ComputedPosition
(RTK)
This log contains the best available position computed by the receiver, along with three status flags. In addition, it
reports other status indicators, including differential lag, which is useful in predicting anomalous behavior brought
about by outages in differential corrections.
This log replaces the P20A log; it is similar, but adds extended status information. With the system operating in an
RTK mode, this log will reflect the latest low-latency solution for up to 30 seconds after reception of the last
reference station observations. After this 30 second period, the position reverts to the best solution available; the
degradation in accuracy is reflected in the standard deviation fields, and is summarized in Table 1-2, Page 17. If
the system is not operating in an RTK mode, pseudorange differential solutions continue for 60 seconds after loss
of the data link, though a different value can be set using the DGPSTIMEOUT command.
PRTKA
Structure:
$PRTKA
L1L2 #high lat
lat σ
posn type idle stn ID *xx
Field # Field type Data Description
week
sec
lag #sv #high
lon
hgt undulation
datum ID
lon σ hgt σ soln status rtk status
[CR][LF]
Example
$PRTKA
1
2
3
4
5
6
$PRTKA
week
sec
Log header
GPS week number
872
GPS time into the week (in seconds)
Differential lag in seconds
174963.00
lag
1.000
#sv
Number of matched satellites; may differ from the number in view.
8
7
#high
Number of matched satellites above RTK mask angle; observations from satellites
below mask are heavily de-weighted
7
8
L1L2 #high Number of matched satellites above RTK mask angle with both L1 and L2 available
7
lat
Latitude of position in current datum, in decimal fraction format. A negative sign implies 51.11358042429
South latitude
9
lon
Longitude of position in current datum, in decimal fraction format. A negative sign
implies West longitude
-114.04358006710
10
11
12
13
14
15
16
17
18
19
20
21
22
hgt
Height of position in current datum, in meters above mean sea level
1059.4105
undulation
datum ID
lat σ
lon σ
hgt σ
soln status
rtk status
posn type
idle
Geoidal separation, in meters, where(+ve) is above ellipsoid and (-ve) is below ellipsoid -16.2617
Standard deviation of latitude solution element, in meters
Standard deviation of longitude solution element, in meters
Standard deviation of height solution element, in meters
Percent idle time, percentage
61
0.0096
0.0100
0.0112
0
0
4
42
stn ID
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Checksum
119
*51
*xx
[CR][LF]
Sentence terminator
[CR][LF]
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Logs summary
Example:
$PRTKA,872,174963.00,1.000,8,7,7,51.11358042429,
-114.04358006710,1059.4105,
-16.2617,61,0.0096,0.0100,0.0112,0,0,4,42,119*51[CR][LF]
PRTKB
Format:
Message ID = 63
Message byte count = 124
Bytes Format
Field #
1
Data
Units
Offset
0
Sync
3
char
(header)
Checksum
1
4
4
4
8
8
4
4
char
3
Message ID
integer
integer
integer
double
4
Message byte count
Week number
8
2
3
4
5
6
weeks
12
16
24
32
36
GPS time into the week
Differential lag
seconds
seconds
Number of matched satellites (00-12)
integer
integer
Number of matched satellites above RTK mask
angle
7
Number of matched satellites above RTK mask
angle with both L1 and L2 available
4
integer
40
8
Latitude
8
8
8
8
4
8
8
8
4
4
4
4
4
double
double
double
double
integer
double
double
double
integer
integer
integer
integer
integer
degrees
degrees
meters
meters
44
9
Longitude
52
10
11
12
13
14
15
16
17
18
19
20
Height above mean sea level
Undulation
60
68
Datum ID
76
Standard deviation of latitude
Standard deviation of longitude
Standard deviation of height
Idle
meters
meters
meters
80
88
96
104
108
112
116
120
Reference station identification (RTCM: 0 - 1023,
or RTCA: 266305 - 15179385)
180
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Logs summary
PVAA/B XYZ Position, Velocity and Acceleration
The PVAA/B logs contain the receiver’s latest computed position, velocity and acceleration in ECEF coordinates.
The position, velocity and acceleration status fields indicate whether or not the corresponding data are valid.
This command supports INS (Inertial Navigation System) integration. PVA logs can be injected into the receiver
from an INS. This information is only used by the tracking loops of the receiver to aid in reacquisition of satellites
after loss of lock, otherwise it is ignored. This command is only useful for very high dynamics where expected
velocity changes during the signal blockage of more than 100 meters per second can occur.
NOTE: These quantities are always referenced to the WGS84 ellipsoid, regardless of the use of the DATUM or
USERDATUM commands.
PVAA
Structure:
seconds
P-z
A-status
$PVAA
week
P-x
P-y
V-x
V-y
*xx
V-z
A-x A-y A-z
P-status V-status
[CR][LF]
Field #
Field type
Data Description
Log header
Example
$PVAA
1
$PVAA
week
seconds
P-x
2
3
4
5
6
7
8
9
10
GPS week number
845
GPS time of week (s)
344559.00
-1634953.141
-3664681.855
4942249.361
-0.025
Position’s X-coordinate (m)
Position’s Y-coordinate (m)
Position’s Z-coordinate (m)
Velocity vector along X-axis (m/s)
Velocity vector along Y-axis (m/s)
Velocity vector along Z-axis (m/s)
P-y
P-z
V-x
V-y
0.140
V-z
0.078
2
A-x
0.000
Acceleration vector along X-axis (m/s )
2
11
12
A-y
A-z
-0.000
0.000
Acceleration vector along Y-axis (m/s )
2
Acceleration vector along Z-axis (m/s )
13
14
15
16
17
P-status
V-status
A-status
*xx
Position status (0 = bad; 1 = good)
Velocity status (0 = bad; 1 = good)
Acceleration status (0 = bad; 1 = good)
Checksum
1
1
1
*02
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$PVAA,845,344559.00,-1634953.141,-3664681.855,4942249.361,-0.025,0.140,
0.078,0.000,-0.000,0.000,1,1,1*02
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Logs summary
PVAB
Format:
Message ID = 49
Field Type
Message byte count = 108
Bytes Format
Field #
Units
Offset
1
Sync
3
1
4
4
4
8
8
8
8
8
8
8
8
char
0
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
double
double
double
double
double
double
double
4
Message byte count
GPS week number
GPS time of week
8
2
3
4
5
6
7
8
9
10
weeks
12
seconds 16
Position vector along X-axis
Position vector along Y-axis
Position vector along Z-axis
Velocity vector along X-axis
Velocity vector along Y-axis
Velocity vector along Z-axis
Acceleration vector along X-axis
meters
meters
meters
m/s
24
32
40
48
56
64
72
m/s
m/s
2
m/s
2
11
12
Acceleration vector along Y-axis
Acceleration vector along Z-axis
8
8
double
double
80
88
96
m/s
2
m/s
13
14
15
Position status
Velocity status
1
1
1
4
4
4
integer
integer
integer
100
104
Acceleration status
1
Only the least-significant bit is used for this flag; the others are reserved for future use.
182
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Logs summary
PXYA/B Computed Cartesian Coordinate Position
This log contains the last valid position, expressed in Cartesian x-y-z space coordinates, relative to the center of
the Earth. The positions expressed in this log are always relative to WGS84, regardless of the setting of the DATUM
PXYA
Structure:
$PXYA week
fix status
seconds
x y z x std y std
z std sol status
diff lag
*xx
[CR][LF]
Data Description
Field #
Field type
$PXYA
week
Example
1
Log header
$PXYA
713
2
GPS week number
3
seconds
x
GPS seconds into the week
488150.00
-1634756.995
-3664965.028
4942151.391
2.335
4
Position x coordinate, in meters
Position y coordinate, in meters
Position z coordinate, in meters
Standard deviation of x, in meters
Standard deviation of y, in meters
Standard deviation of z, in meters
Solution status as listed in Table D-1
5
y
6
z
7
x std
y std
z std
sol status
fix status
8
3.464
9
4.156
10
11
0
0 =
1 =
2 =
fix not available or invalid
Single point stand-alone fix
Differential fix
2
1
12
Age of differential correction (seconds) (= 0 if fix status ≠ 2)
0.4
diff lag
*xx
13
14
Checksum
*08
[CR][LF]
Sentence terminator
[CR][LF]
1
This log provides differential fix and lag status.
Example:
$PXYA,713,488150.00,-1634756.995,-3664965.028,4942151.391,2.335,3.464,
4.156,0,2,0.4*08[CR][LF]
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Logs summary
PXYB
Format:
Message ID = 26
Message byte count = 88
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
1
4
4
4
8
8
8
8
8
8
8
4
0
3
4
8
(header)
Checksum
char
Message ID
Message byte count
Week number
Seconds of week
x
integer
integer
integer
double
double
double
double
double
double
double
integer
integer
2
weeks
12
3
seconds 16
4
meters
meters
meters
meters
meters
meters
24
32
40
48
56
64
72
76
5
y
6
z
7
StdDev of x
StdDev of y
StdDev of z
Solution status
8
9
10
11
1
4
Fix status
1
12
8
double
seconds 80
Differential lag, age of differential corrections
1
This log provides differential fix and lag status.
184
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Logs summary
RALA/B
Raw Almanac
Almanac and health data are contained in subframes four and five of the satellite broadcast message. Subframe four
contains information for SVs 25-32, as well as ionospheric, UTC and SV configuration data. Subframe five contains
information for SVS 1-24.
Subframes four and five each contain 25 pages of data, and each page contains ten 30-bit words of information as
transmitted from the satellite. The RALA/B log outputs this information with parity bits checked and removed (ten
words - 24 bits each). The log will not be generated unless all ten words pass parity.
This log will alternately report each page from subframes four and five as they are collected. Logging this log
onnew would be the optimal logging rate to capture data from pages in subframes four and five as they are received.
RALA logs contain a hex representation of the raw almanac data (one of the possible 25 pages of either subframe 4
or 5). RALB contains the raw binary information.
RALA
Structure:
$RALA chan # prn subframe *xx [CR][LF]
Field #
Field type
$RALA
chan #
Data Description
Example
1
2
3
4
Log header
$RALA
7
Channel number collecting almanac data (0-11)
PRN of satellite from which data originated
prn
16
subframe
Subframe 4 or 5 of almanac data
(60 hex characters)
8B0A54852C964C661F086366FDBE00A
10D53DA6565F2503DD7C2AACBFED3
5
6
*xx
Checksum
*05
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$RALA,7,16,8B0A54852C964C661F086366FDBE00A10D53DA6565F2503DD7C2AACBFED3
*05[CR][LF]
RALB
Format:
Message ID = 15
Message byte count = 52
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
0
(header)
Checksum
1
char
3
Message ID
4
integer
integer
integer
integer
char
4
Message byte count
Channel number, 0-11
PRN number, 1-32
Almanac data, data [30]
Filler bytes
4
8
2
3
4
5
4
12
16
20
50
4
30
2
char
186
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Logs summary
RASA/B
Raw Almanac Set
This is a single log for the entire Almanac data set. Only a complete log will be set so you do not have to worry
about ephemeris data imitating an Almanac.
RASA
Structure:
$RASA
subframe#
:
RxWeek
page #
RxSec
AlmWeek Toa RxPrn # subframes
subframe
subframe#
*xx
page #
subframe
[CR][LF]
Field #
Field type
$RASA
Data Description
Example
1
2
3
4
5
6
7
8
9
10
Log header
$RASA
926
246000
926
319488
1
RxWeek
RxSec
GPS week data received
Approximate GPS seconds into week data received
Almanac reference week
AlmWeek
Toa
Almanac reference seconds
PRN of satellite from which data originated
Number of subframes to follow
Subframe Number
RxPrn
# subframes
subframe #
page #
30
4
Page Number
2
8B0E784FDA315936EC4EF
CAEFD3600A10C5C896ECE
9412862BD1AEFF0006
subframe
Subframe of almanac data (60 hex characters, variable
length up to 50 lines of subframe data ≅ 3300 bytes)
...
...
...
...
...
...
Next subframe #, page # and subframe ...
...
Last subframe #, page # and subframe
variable
variable
*xx
Checksum
*32
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$RASA,926,246000,926,319488,1,30,4,2,8B0E784FDA315936EC4EFCAEFD3600A10C5C896ECE9412862BD1AEFF
0006,4,3,8B0E784FDCB05A51184E0A26FD4C00A10DB2609586F2BE804B917BFCFFFB,4,4,8B0E784FDF315B65654
EFF68FD3A00A10CF78A21497D29E4D4504D000013,4,7,8B0E784FE6B15D2D014E07D2FD4800A10ADF5F8CDBAF9F5
720A25C22FF95,4,8,8B0E784FE9315E28E84E057AFD4600A10D1EB58EE4421223816DB8FFFFF7,4,9,8B0E784FEB
B35F3D354E0BD6FD3C00A10D55E000EB1D3D371F95C8000001,4,17,8B0E784FFFB0773246204E524B414D4F444C3
54E204E38342F5A563822A8,4,18,8B0E78500232780C00FF002C00FD00000000000000034E9E0C90020CAAA9,4,2
5,8B0E785013B27F9999999099009999999099999990999080000FC0000FE8,5,1,8B0E784FD835411ED34E0835FD
4900A10C1A615B4ABE261433AAC3040001,5,2,8B0E784FDAB7428CFE4EFECDFD4000A10CF6B3DFACA157B083EBA2
CAFFE4,5,3,8B0E784FDD354314234E060EFD3600A10CD5DFDCCC69CB36EB45F407003C,5,4,8B0E784FDFB744236
74E15B4FD4800A10C850BB1F6DB53D7E65BA6060034,5,5,8B0E784FE2344509CB4E00A7FD3F00A10BEFB48EACD93
58704D58E0F000A,5,6,8B0E784FE4B54637BD4E0AB8FD3B00A10CF5E1492D95D0B001BEF6000000,5,7,8B0E784F
E734474DE04E0C34FD3F00A10C57DFEF88A2B87952974463000A,5,9,8B0E784FEC344936594E0150FD3C00A10C5D
8AC38E0990CA01A8D3FE0004,5,10,8B0E784FEEB64A127F4E0E0BFD5100A10C72359FC2F5A04887F78A01001B,5,
13,8B0E784FF6374D0F544E0AA8FD4CFFA10EF2604E7FB038A9C9152201FFDB,5,14,8B0E784FF8B44E0C634E119F
FD5800A10DBD37674077E0355E13D7030002,5,15,8B0E784FFB354F39E64E1902FD4D00A10D6F0D3E5342A05AC4A
F843E0030,5,16,8B0E784FFDB45012294E0F48FD5400A10CA537A8C902C525BD198A040006,5,17,8B0E78500036
514FC34E19C3FD5100A10CCC0EC06367883FFB1622EA0018,5,18,8B0E785002B45238A44E0107FD3E00A10C455F0
43F43BCBA529078000018,5,19,8B0E78500536531AF54EF68FFD2D00A10D2D88F669888C38E202CA2100BD,5,21,
8B0E78500A355570FE4E0D99FD5200A10D0835E0458927E898247B0B0028,5,22,8B0E78500CB45653134EFEC6FD3
D00A10C1AB4776508EC2C7C0DFB02003D,5,23,8B0E78500F355763534E0FAAFD5400A10CF8376A23AA2FFC8D65B2
000017,5,24,8B0E785011B6583FB74E1C1EFD5200A10D8D0BCB65B2EAD8F641D8650050,5,25,8B0E78501435734
E9E00000000003F000FFFFC000000003F000000AAAAAB*39
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Logs summary
RASB
Format:
Message ID = 66
Message byte count = 40 + (n * 32)
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
4
4
4
4
1
1
0
Checksum
char
3
Message ID
integer
integer
integer
double
integer
integer
integer
integer
char
4
Message byte count
8
2
Week data received
weeks
12
16
24
28
32
36
40
41
3
Approximate seconds into week data received
Almanac reference week
Almanac reference seconds
PRN of satellite from which data originated
Number of subframes to follow
Subframe number
seconds
weeks
4
5
seconds
6
7
8
9
Page number
char
10...
Next PRN offset = 40 + (obs *32)
Note: Variable Length = 40 + (n * 32). Maximum = 40 + (50 * 32) = 1640.
Typical size (31 subframes) = 1032 bytes.
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Logs summary
RBTA/B Satellite Broadcast Data: Raw Bits
This message contains the satellite broadcast data in raw bits before FEC (forward error correction) decoding or
any other processing. An individual message is sent for each PRN being tracked. For a given satellite, the message
number increments by one each time a new message is generated. This data matches the SBTA/B data if the
message numbers are equal. The data must be logged with the ’onnew’trigger activated to prevent loss of data.
RBTA
Structure:
$RBTA week
raw bits
seconds
prn cstatus
message # # of bits
*xx [CR][LF]
Field #
Field type
Data Description
Example
$RBTA
1
2
3
4
5
6
7
$RBTA
week
Log header
GPS week number
883
seconds
prn
GPS seconds into the week
413908.000
115
PRN of satellite from which data originated
Channel Tracking Status
cstatus
message #
# of bits
80812F14
119300
Message sequence number
Number of bits transmitted in the message. At present,
always equals 256 bits.
256
8
raw bits
256 bits compressed into a 32 bytes. Hence, 64 hex
characters are output.
30FB30FB30FB30F878DA621
94000F18322931B9EBDBC1C
BC9324B68FBDAEBE8A
9
*xx
Checksum
*42
10
[CR][LF]
Sentence terminator
[CR][LF]
RBTB
Format:
Message ID = 52
Data
Message byte count = 72
Bytes Format
char
Field #
Units
Offset
1
Sync
3
1
4
4
4
8
4
4
4
4
32
0
(header)
Checksum
char
3
Message ID
Message byte count
Week number
Seconds of week
PRN number
Channel Status
Message #
integer
integer
integer
double
integer
integer
integer
integer
char
4
bytes
8
2
3
4
5
6
7
8
weeks
seconds
1-999
n/a
12
16
24
28
32
36
40
n/a
# of Bits
n/a
Raw Bits
n/a
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Logs summary
RCCA
Receiver Configuration
This log outputs a list of all current GPSCard command settings. Observing this log is a good way to monitor the
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Logs summary
RCSA/B
Receiver Status
The RCSA log will always output four records: one for VERSION, one for receiver CHANNELS, one for receiver CPU
IDLE time, and one indicating receiver self-testSTATUS. However, RCSB will embed the same information in a single
record.
Together, the RVSA/B and VERA/B logs supersede the RCSA/B logs. In other word this log is soon to be obsolete and
eventually will be no longer supported. It is recommended then that you use the RVSA/B and VERA/B logs.
RCSA
Structure:
$RCSA
$RCSA
$RCSA
$RCSA
VERSION sw ver
CHANNELS # chans
*xx [CR][LF]
*xx [CR][LF]
IDLE
idle time *xx [CR][LF]
rec status *xx [CR][LF]
STATUS
Log
Data Identifier
Data Description
Checksum String End
$RCSA
VERSION
sw ver: Software information indicating model, S/N, S/W
version and S/W version date
*xx
[CR][LF]
$RCSA
$RCSA
CHANNELS
IDLE
# chans: Indicates number of parallel channels on GPSCard *xx
idle time: An integer number representing percent idle time *xx
for the CPU, with a valid range of 0 to 99
[CR][LF]
[CR][LF]
$RCSA
STATUS
rec status: Indicates result of hardware self-test and software *xx
[CR][LF]
Example:
$RCSA,VERSION,GPSCard-2 3951R LGR94160001 HW 16 SW 3.15 Mar 31/94*16
$RCSA,CHANNELS,10*12
$RCSA,IDLE,40*03
$RCSA,STATUS,000007F6*60
The status code is a hexadecimal number representing the results of the GPSCard BIST test and software status. As
an example, the status code ’000000F6’indicates that the GPSAntenna is not working properly or is disconnected
and the GPSCard is good, while ’000000F7’indicates that the GPSAntenna and the GPSCard are both functioning
properly. See Table D-5, Page 196 for a detailed description of the status code. Bit 0 is the least significant bit of
the status code and Bit 16 is the most significant bit.
RCSB
Format:
Message ID = 13
Message byte count = 100
Bytes Format
char
Field #
Data
Offset
1
Sync
3
1
4
4
80
1
1
2
4
0
3
4
8
(header) Checksum
Message ID
char
integer
integer
char
Message byte count
Software version #, ASCII
2
3
4
5
6
12
92
93
94
96
Number of receiver channels
CPU idle time, percent
Filler
char
char
bytes
integer
Self-test status
NOTE 1: See Table D-5 for a detailed GPSCard Receiver Self-test Status Code table and bit descriptions.
NOTE 2: Self test bits 2, 3, 4, 6, 7 are set only once when the GPSCard is first powered up. All other bits are set
by internal test processes each time the RCSA/B log is output.
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Logs summary
REPA/B
Raw Ephemeris
REPA
This log contains the raw Binary information for subframes one, two and three from the satellite with the parity
information removed. Each subframe is 240 bits long (10 words - 24 bits each) and the log contains a total 720 bits
(90 bytes) of information (240 bits x 3 subframes). This information is preceded by the PRN number of the satellite
from which it originated. This message will not be generated unless all 10 words from all 3 frames have passed
parity.
Ephemeris data whose toe (time of ephemeris) is older than six hours will not be shown.
Structure:
$REPA prn
subframe1 subframe2 subframe3 *xx [CR][LF]
Field #
Field type
$REPA
Data Description
Example
1
2
3
Log header
$REPA
14
prn
PRN of satellite from which data originated
subframe1
Subframe 1 of ephemeris data (60 hex characters)
8B09DC17B9079DD7007D5D
E404A9B2D
04CF671C6036612560000021
804FD
4
5
subframe2
subframe3
Subframe 2 of ephemeris data (60 hex characters)
Subframe 3 of ephemeris data (60 hex characters)
8B09DC17B98A66FF713092F
12B359D
FF7A0254088E1656A10BE2F
F125655
8B09DC17B78F0027192056E
AFFDF2724C
9FE159675A8B468FFA8D066
F743
6
7
*xx
Checksum
*57
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$REPA,14,8B09DC17B9079DD7007D5DE404A9B2D04CF671C6036612560000021804FD,
8B09DC17B98A66FF713092F12B359DFF7A0254088E1656A10BE2FF125655,
8B09DC17B78F0027192056EAFFDF2724C9FE159675A8B468FFA8D066F743*57[CR][LF]
REPB
Format:
Message ID = 14
Message byte count = 108
Field #
Data
Bytes
Format
char
Offset
1
Sync
3
1
4
4
4
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
integer
char
Message byte count
PRN number, 1-32
2
12
3-4-5
Ephemeris data, data [90] 90
Filler bytes
16
2
char
106
192
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D
Logs summary
RGEA/B/D
Channel Range Measurements
RGEA/B/D contain the channel range measurements for the currently observed satellites. The RGED message is
a compressed form of the RGEB message. When using these logs, please keep in mind the constraints noted along
with the description.
It is important to ensure that the receiver clock has been set and can be monitored by the bits in the rec-status field.
Large jumps in range as well as ADR will occur as the clock is being adjusted. If the ADR measurement is being
used in precise phase processing it is important not to use the ADR if the "parity known" flag in the ch-tr-status
field is not set as there may exist a half (1/2) cycle ambiguity on the measurement. The tracking error estimate of
the pseudorange and carrier phase (ADR) is the thermal noise of the receiver tracking loops only. It does not
account for possible multipath errors or atmospheric delays.
RGEA and RGEB contain all of the new extended channel tracking status bits (see Table D-7, Page 201), while
RGED contains only the lowest 24 bits. The receiver self-test status word (see Table D-5, Page 196) now also
indicates L2, OCXO and new almanac status.
If both the L1 and L2 signals are being tracked for a given PRN, two entries with the same PRN will appear in the
range logs. As shown in Table D-7 (Channel Tracking Status), these entries can be differentiated by bit 19, which
is set if there are multiple observables for a given PRN, and bit 20, which denotes whether the observation is for
L1 or L2. This is to aid in parsing the data.
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Logs summary
RGEA
Structure:
$RGEA
week
seconds # obs
rec status
prn
:
psr psr std adr
adr std
dopp C/No locktime ch-tr-status
dopp C/No locktime ch-tr-status
prn
*xx
psr psr std adr
[CR][LF]
adr std
Field #
Field type
Data Description
Example
$RGEA
1
2
3
4
5
$RGEA
week
Log header
GPS week number
845
seconds
# obs
GPS seconds into the week
511089.00
14
Number of satellite observations with information to follow
1
rec status
000B20FF
4
6
prn
Satellite PRN number (1-32) of range measurement
Pseudorange measurement (m)
7
psr
23907330.296
0.119
8
psr std
adr
Pseudorange measurement standard deviation (m)
Carrier phase, in cycles (accumulated Doppler range)
Estimated carrier phase standard deviation (cycles)
Instantaneous carrier Doppler frequency (Hz)
Signal to noise density ratio C/N = 10[log (S/N )] (dB-Hz)
9
-125633783.992
0.010
10
11
12
adr std
dopp
3714.037
44.8
C/N
0
0
10
0
13
14
locktime
Number of seconds of continuous tracking (no cycle slipping)
1928.850
82E04
ch-tr-status
Hexadecimal number indicating phase lock, channel number and channel
tracking state, as shown in Table D-7.
...
...
...
...
...
...
Next PRN #, psr, psr std, adr, adr std, dopp, C/No, locktime,ch-tr-status
...
Last PRN #, psr, psr std, adr, adr std, dopp, C/No, locktime, ch-tr-status
variable
variable
*xx
Checksum
*30
[CR][LF]
Sentence terminator
[CR][LF]
1
This output will always be a hexadecimal representation which must be converted to binary format. In this example, the conversion gives
00000000000010110010000011111111 in binary format, see Appendix H, Page 236 for a complete conversion list. Reading from right to left
you can look to see what each bit represents in Table D-5, following.
Example (carriage returns have been added between observations for clarity):
$RGEA,845,511089.00,14,000B20FF
4,23907330.296,0.119,-125633783.992,0.010,3714.037,44.8,1928.850,82E04,
4,23907329.623,1.648,-97896180.284,0.013,2894.285,35.0,1746.760,582E0B,
2,21298444.942,0.040,-111954153.747,0.006,-1734.838,54.2,17466.670,82E14,
2,21298444.466,0.637,-87236867.557,0.006,-1351.607,43.3,17557.260,582E1B,
9,22048754.383,0.063,-115874135.450,0.006,2174.006,50.4,5489.100,82E24,
9,22048754.424,0.641,-90291443.071,0.006,1694.238,43.2,5489.100,582E2B,
15,23191384.847,0.261,-121887295.980,0.017,-2069.744,38.0,9924.740,82E34,
15,23191384.663,0.596,-94977002.452,0.010,-1612.587,43.8,9881.830,582E3B,
26,24063897.737,0.199,-126477739.189,0.014,-2654.682,40.3,12821.640,82E54,
26,24063898.913,1.043,-98553986.239,0.013,-2068.380,39.0,12793.280,582E5B,
7,20213352.139,0.037,-106237901.461,0.005,439.943,55.0,10313.040,82E74,
7,20213351.196,0.498,-82782498.454,0.007,343.020,45.4,9977.400,582E7B,
27,24393726.829,0.123,-128229016.323,0.012,-4047.338,44.5,22354.119,82E94,
27,24393728.057,1.805,-99918535.513,0.013,-3153.559,34.2,22301.830,582E9B
*30
194
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D
Logs summary
RGEB
Format:
Message ID = 32
Message byte count = 32 + (obs x 44)
Field #
1
Data
Bytes
Format
char
Units
Offset
0
Sync
3
(header)
Checksum
1
4
4
4
8
4
4
4
8
4
8
4
4
4
char
3
Message ID
integer
integer
integer
double
integer
integer
integer
double
float
4
Message byte count
8
2
Week number
weeks
12
16
24
28
32
36
44
48
56
60
64
3
Seconds of week
seconds
4
Number of observations (obs)
Receiver self-test status
PRN
5
6
7
Pseudorange
meters
meters
8
StdDev pseudorange
Carrier phase - accumulated Doppler range, cycles
StdDev - accumulated Doppler range, cycles
Doppler frequency
9
double
float
10
11
12
float
Hz
C/N
0
float
dB-Hz
13
Locktime
4
4
float
seconds
68
72
14
Tracking status
integer
15...
Next PRN offset = 32 + (obs x 44)
RGED
Format:
Message ID = 65
Message byte count =24 + (20 x number of obs)
Field #
Data
Bytes
Format
Scale
Offset
1
Sync
3
1
4
4
2
2
4
4
char
0
(header) Checksum
Message ID
char
3
integer
integer
4
Message byte count
Number of obs
8
2
3
4
5
6
1
12
14
16
20
24
Week number
1
Seconds of week
Receiver status
integer
integer
1/100
1
First PRN range record
20
Next PRN offset = 24 + (20 x number of obs)
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Logs summary
Table D-5 Receiver Self-Test Status Codes
N7
N
6
N 5
N 4
N 3
N 2
N 1
N 0
<- Nibble
<- Number
Bit Description Range Values
lsb ANTENNA
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Hex Value
00000001
1 = good, 0 = bad
=
0
1
2
3
4
5
6
7
8
9
L1 PLL
RAM
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = not set, 0 = set
1 = not set, 0 = set
00000002
00000004
00000008
00000010
00000020
00000040
00000080
00000100
00000200
ROM
DSP
L1 AGC
COM 1
COM 2
WEEK
NO
COARSETIME
10 NO FINETIME
1 = not set, 0 = set
00000400
00000800
00001000
00002000
00004000
11 L1 JAMMER
1 = present, 0 = normal
12 BUFFER COM 1 1 = overrun, 0 = normal
13 BUFFER COM 2 1 = overrun, 0 = normal
14 BUFFER
CONSOLE
1 = overrun, 0 = normal
15 CPU OVERLOAD 1 = overload, 0 = normal 00008000
16 ALMANAC
SAVED IN NVM
1 = yes, 0 = no
00010000
17 L2 AGC
1 = good, 0 = bad
1 = present, 0 = normal
1 = good, 0 = bad
1 = good, 0 = bad
1 = yes, 0 = no
00020000
00040000
00080000
00100000
00200000
18 L2 JAMMER
19 L2 PLL
20 OCXO PLL
21 SAVED ALMA.
NEEDS UPDATE
22 ALMANAC
INVALID
23 POSITION
SOLUTION
1=invalid, 0=valid
1=invalid, 0=valid
00400000
00800000
INVALID
24 POSITION FIXED 1 = yes, 0 = no
01000000
02000000
25 CLOCK MODEL 1=invalid, 0=valid
INVALID
26 CLOCK
STEERING
1 = disabled, 0 = enabled 04000000
DISABLED
27 RESERVED
28- RESERVED
31
196
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Logs summary
Notes on Table D-5:
1. Bit 3: On OEM GPSCards, “ROM” includes all forms of non-volatile memory.
2. Bits 12-15: Flag is reset to 0 five minutes after the last overrun/overload condition has occurred.
GPSCard example: All OK = 0000 0000 0000 1010 0000 0000 1111 1111 (binary) = 000A00FF (hexadecimal); using a VCTCXO oscillator.
RECEIVER STATUS - DETAILED BIT DESCRIPTIONS OF SELF-TEST
Bit 0
Antenna
1
0
This bit will be set to 1 if the antenna connection is not drawing excessive current.
If the antenna connections are shorted together then this bit will be clear (0) indicating a possible antenna
port problem.
Bit 1
L1 PLL
1
0
When the L1 RF downconverter passes self-test, the bit will be set to 1.
If a fault is detected in the L1 RF downconverter, this bit is set to 0.
Bit 2
RAM
1
0
When this bit is set to 1, the receiver RAM has passed the self-test requirements.
If the bit has been set to 0, then RAM test has failed; please contact NovAtel Customer Service.
Bit 3
ROM (Note: “ROM” includes all forms of nov-volatile memory (NVM))
When this bit is set to 1, the receiver ROM test has passed the self test requirements.
A zero bit indicates the receiver has failed the ROM test.
1
0
Bit 4
DSP
1
0
This bit will be set to 1 when the digital signal processors (DSP) have passed the self-test requirements.
0 indicates one or both of the DSP chips has failed self-test; please contact NovAtel Customer Service.
Bit 5
L1 AGC
1
When set to 1, the L1AGC circuits are operating within normal range of control.
0
This bit will be set clear if the L1 AGC is operating out of normal range. Intermittent setting of the AGC bit
indicates that the card is experiencing some electro-magnetic interference of a very short duration.
Continuous setting of the AGC bit may indicate that the card is receiving too much signal power from the
antenna or that a more serious problem with the card may exist. Failure of this test could be the result of
various possibilities, such as: bad antenna LNA, excessive loss in the antenna cable, faulty RF
downconverter, or a pulsating or high power jamming signal causing interference. If this bit is
continuously set clear, and you cannot identify an external cause for the failed test, please contact
NovAtel Customer Service.
Bit 6
COM1
1
0
When set to 1, the COM1 UART has passed the self-test requirements.
If set to 0, the COM1 UART has failed self-test and cannot be used for reliable communications.
Bit 7
COM2
1
0
When set to 1, the COM2 UART has passed the self-test requirements.
If set to 0, the COM2 UART has failed self-test and cannot be used for reliable communications.
Bits 8, 9, 10 Week / No Coarsetime / No Finetime
0
These bits indicate the state of the receiver time and are set only once, generally in the first few minutes
of operation, in the presence of adequate numbers of satellite signals to compute position and time.
1
If these bits are not all set to zero, then the observation data, pseudorange measurement, carrier phase, and
Doppler measurements may jump as the clock adjusts itself.
Bit 11 L1 Jammer Detection
0
Normal operation is indicated when this bit is 0.
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If set to 1, the receiver has detected a high power signal causing interference. When this happens, the
1
receiver goes into a special anti-jamming mode where it re-maps the A/D decode values as well as special
L1AGC feedback control. These adjustments help to minimize the loss that will occur in the presence of a
jamming signal. You should monitor this bit, and if set to 1, do your best to remedy the cause of the
jamming signal. Nearby transmitters or other electronic equipment could be the cause of interference;
you may find it necessary to relocate your antenna position if the problem persists.
Bits 12, 13, 14 Buffer COM 1 / COM 2
0
1
Normal operation is indicated by a 0 value.
These bits are set to 1 to inform the user when any of the 8-Kilobyte output buffers have reached an over-
run condition (COM1 or COM2). Over-run is caused by requesting more log data than can be taken off the
GPSCard because of bit rate limitations or slow communications equipment. If this happens, the new data
attempting to be loaded into the buffer will be discarded. The receiver will not load a partial data record
into an output buffer. The flag resets to 0 five minutes after the last overrun occurred.
Bit 15 CPU Overload
0
1
Normal operation is indicated by a 0 value.
A value of 1 indicates that the CPU is being over-taxed. This may be caused by requesting an excessive
amount of information from the GPSCard. If this condition is occurring, limit redundant data logging or
change to using binary data output formats, or both. You should attempt to tune the logging requirements
to keep the idle time above 20% for best operation. If the average idle % drops below 10% for prolonged
periods of time (2-5 seconds), critical errors may result in internal data loss and the over-load bit will be
set to 1. You can monitor the CPU % idle time by using the RvSA log message. The flag resets to 0 five
minutes after the first overload occurred.
NOTE: As the amount of CPU power becomes limited, the software will begin to slow down the position
calculation rate. If the CPU becomes further limited, the software will begin to skip range measurement
processing. Priority processing goes to the tracking loops.
Bit 16 Almanac Saved
0
1
Almanac not saved in non-volatile memory.
Almanac saved in non-volatile memory (12 channel OEM cards only).
Bit 17 L2 AGC
1
0
When set to 1, the L2 AGC circuits are operating within normal range of control.
This bit will be set clear if the L2 AGC is operating out of normal range. Intermittent setting of the AGC bit
indicates that the card is experiencing some electro-magnetic interference of a very short duration.
Continuous setting of the AGC bit may indicate that the card is receiving too much signal power from the
antenna or that a more serious problem with the card may exist. Failure of this test could be the result of
various possibilities, such as: bad antenna LNA, excessive loss in the antenna cable, faulty RF
downconverter, or a pulsating or high power jamming signal causing interference. If this bit is
continuously set clear, and you cannot identify an external cause for the failed test, please contact NovAtel
Customer Service.
Bit 18 L2 Jammer Detection
0
1
Normal operation is indicated when this bit is 0.
If set to 1, the receiver has detected a high power signal causing interference. When this happens, the
receiver goes into a special anti-jamming mode where it re-maps the A/D decode values as well as special
L2AGC feedback control. These adjustments help to minimize the loss that will occur in the presence of a
jamming signal. You should monitor this bit, and if set to 1, do your best to remedy the cause of the
jamming signal. Nearby transmitters or other electronic equipment could be the cause of interference; you
may find it necessary to relocate your antenna position if the problem persists.
Bit 19 L2 PLL
1
0
When the L2 RF downconverter passes self-test, the bit will be set to 1.
If a fault is detected in the L2 RF downconverter, this bit is set to 0.
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Logs summary
Bit 20 OCXOPLL
1
0
When an external oscillator is connected and the OCXOPLL bit passes self-test, the bit will be set to 1.
If no external oscillator is detected or a fault is detected in the OCXOPLL bit, this bit is set to 0.
Bit 21 Saved Almanac Needs Update
1
When the almanac received is newer than the one currently stored in NVM (non-volatile memory), the
bit will be set to 1.
0
This bit will be set to 0 if an almanac has not been received that is newer than the one stored in memory.
Bit 22 Almanac Invalid
1
0
No almanac in use
Valid almanac in use
Bit 23 Position Solution Invalid
1
0
Position solution is not valid
Valid position computed
Bit 24 Position Fixed
1
0
A fix position command has been accepted
Position has not been fixed
Bit 25 Clock Model Invalid
1
0
Clock model has not stabilized
Clock model is valid
Bit 26 Clock Steering Disabled
1
0
Clockadjust disable command has been accepted
Clockadjust is enabled
Table D-6 Range Record Format (RGED only)
Data
Bit(s) from first to last
Length (bits)
Format
integer
Scale Factor
1A, 1B
0..5
6
1
PRN
2
3
4
6..10
11.31
32..63
5
integer
(20+n) dB-Hz
1/32 s
C/No
21
32
integer
Lock time
ADR
integer 2’s comp.
1/256 cycles
Doppler frequency
Pseudorange
68..95
28
36
4
integer 2’s comp.
integer 2’s comp.
integer
1/256 Hz
64..67 msn; 96..127 lsw
128..131
1/128 m
StdDev - ADR
(n+1) / 512 cyc
5
StdDev - pseudorange
132..135
4
see
6
136..159
24
integer
Channel Tracking status
Notes on Table D-6:
1A
Only PRNs 1 - 63 are reported correctly (Note: while there are only 32 PRNs in the basic GPS scheme,
situations exist which require the use of additional PRNs)
1B
2
The prn offsets for WAAS have been mapped to the same range as GPS, ie. 1 - 19, while the prn offsets
for GLONASS are 1 - 29.
C/No is constrained to a value between 20 - 51 dB-Hz. Thus, if it is reported that C/No = 20 dB-Hz, the
actual value could be less. Likewise, if it is reported that C/No = 51 dB-Hz, the true value could be greater.
3
Lock time rolls over after 2,097,151 seconds.
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4
Logs summary
ADR (Accumulated Doppler Range) is calculated as follows:
ADR_ROLLS = ( -RGED_PSR / WAVELENGTH - RGED_ADR) / MAX_VALUE
Round to the closest integer
IF (ADR_ROLLS ≤ -0.5)
ADR_ROLLS = ADR_ROLLS - 0.5
ELSE
ADR_ROLLS = ADR_ROLLS + 0.5
At this point integerise ADR_ROLLS
CORRECTED_ADR = RGED_ADR + (MAX_VALUE * ADR_ROLLS)
where:
ADR has units of cycles
WAVELENGTH = 0.1902936727984 for L1
WAVELENGTH = 0.2442102134246 for L2
MAX_VALUE = 8388608
5
Code
0
RGED
0.000 to 0.050
0.051 to 0.075
0.076 to 0.113
0.114 to 0.169
0.170 to 0.253
0.254 to 0.380
0.381 to 0.570
0.571 to 0.854
0.855 to 1.281
1.282 to 2.375
2.376 to 4.750
4.751 to 9.500
9.501 to 19.000
19.001 to 38.000
38.001 to 76.000
76.001 to 152.000
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
6
Only bits 0 - 23 are represented in the RGED log
200
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Logs summary
Table D-7 Channel Tracking Status
N 7
N 6
N 5
N 4
N 3
N 2
N 1
N 0
<- <- Nibble Number
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Bit
lsb=0
Description
Range Values
Hex.
1
1
2
3
4
5
Tracking state
0 - 11 See below
2
4
8
10
20
0 - n (0=first, n=
last)
6
7
8
9
Channel number
Phase lock flag
(n depends on GPSCard) 40
80
100
1 = Lock, 0 = Not locked 200
10 Parity known flag
1 = Known, 0 = Not
known
400
11 Code lockedflag
1 = Lock, 0 = Not locked 800
12
1000
13 Correlator spacing
0 - 7 See below
2000
4000
14
15
0=GPS 3= Pseudolite 8000
GPS
16 Satellitesystem
1=GLONASS 4-7
Reserved
10000
17
2=WAAS
20000
40000
80000
18 Reserved
19 Grouping
1 = Grouped, 0 = Not
grouped
20 Frequency
21 Code type
1 = L2, 0 = L1
100000
200000
0 = C/A 2 = P-
codeless
22
1 =P
3= Reserved 400000
23 Forward error correction
1 = FEC enabled, 0 = no 800000
FEC
24
:
Reserved
29
30 External range
1 = Ext. range, 0 = Int.
range
31 Channel assignment
1 = Forced, 0 =
Automatic
Table D-7 is referenced by the ETSA/B, FRMA/B, RGEA/B/D and WRCA/B logs.
Table D-7, Bits 0 - 3: Channel Tracking State
State
Description
State
Description
L1 Steering
0
1
2
3
4
5
L1 Idle
6
L1 Sky search
7
L1 Frequency-lock loop
L2 Idle
L1 Wide frequency band pull-in
L1 Narrow frequency band pull-in
L1 Phase-lock loop
8
9
L2 P-code alignment
L2 Search
10
11
L1 Re-acquisition
L2 Phase-lock loop
Higher numbers are reserved for future use
Table D-7, Bits 12-14: Correlator Spacing
State
Description
0
1
2
Unknown: this only appears in versions of software previous to x.45, which didn’t use this field
Standard correlator: spacing = 1 chip
Narrow Correlator tracking technology: spacing < 1 chip
Higher numbers are reserved for future use
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Logs summary
RINEX
The Receiver-Independent Exchange (RINEX) format is a broadly-accepted, receiver-independent format for
storing GPS data. It features a non-proprietary ASCII file format that can be used to combine or process data
generated by receivers made by different manufacturers. RINEX was originally developed at the Astronomical
Institute of the University of Berne. Version 2, containing the latest major changes, appeared in 1990;
subsequently, minor refinements were added in 1993. To date, there are three different RINEX file types
observation files, broadcast navigation message files and meteorological data files.
202
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Logs summary
RPSA/B Reference Station Position and Health
This log contains the ECEF XYZ position of the reference station as received through the RTCA Type 7 or RTCM
Type 3 message. It also features a time tag, the health status of the reference station, and the station ID. This
information is set at the reference station using the FIX POSITION command.
RPSA
Structure:
$RPSA week
seconds
X
Y
Z health
stn ID
*xx
[CR][LF]
Example
Field #
Field type
Data Description
1
2
3
4
$RPSA
Log header
$RPSA
872
week
GPS week number
seconds
GPS time into the week (seconds)
ECEF X value (meters)
174962.00
1
1
1
-1634962.8660
X
Y
5
6
ECEF y value (meters)
ECEF z value (meters)
Reference Station Health
-3664682.4140
4942301.3110
Z
7
8
health
stn ID
0
Reference station identification (RTCM: 0 - 1023, or
RTCA: 266305 - 15179385)
119
9
*xx
Checksum
*32
10
[CR][LF]
Sentence terminator
[CR][LF]
Note:
1
If (X, Y, Z) = (0,0,0) then a reference station position has not yet been determined.
Example:
$RPSA,872,174962.00,-1634962.8660,-3664682.4140,4942301.3110,0,119*32[CR][LF]
RPSB
Format:
Message ID = 60
Message byte count = 56
Field #
Data
Bytes
Format
char
char
Units
Offset
0
1
Sync
3
1
4
4
4
8
8
8
8
4
4
(header)
Checksum
3
Message ID
integer
integer
integer
double
double
double
double
integer
integer
4
Message byte count
GPS week number
GPS time into the week
ECEF X value
8
2
3
4
5
6
7
8
weeks
12
16
24
32
40
48
52
seconds
meters
meters
meters
ECEF Y value
ECEF Z value
Reference station health
Referencestationidentification(RTCM:0-1023,
or RTCA: 266305 - 15179385)
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Logs summary
RTCA Standard Logs
The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support Differential
Global Navigation Satellite System (DGNSS) Special Category I (SCAT-I) precision instrument approaches. The
RTCA Standard is in a preliminary state. NovAtel’s current support for this Standard is based on "Minimum
Aviation System Performance Standards DGNSS Instrument Approach System: Special Category I (SCAT-I)" dated
August 27, 1993 (RTCA/DO-217).
RTCM Standard Logs
The Radio Technical Commission for Maritime Services (RTCM) was established to facilitate the establishment of
various radio navigation standards, which includes recommended GPS differential standard formats.
The standards recommended by the Radio Technical Commission for Maritime Services Special Committee 104,
Differential GPS Service (RTCM SC-104,Washington, D.C.), have been adopted by NovAtel for implementation
into the GPSCard. Because the GPSCard is capable of utilizing RTCM formats, it can easily be integrated into
positioning systems around the globe.
204
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Logs summary
RTKA/B Computed Position - Time Matched
RTK
This log represents positions that have been computed from time matched reference and remote observations.
There is no reference station extrapolation error on these positions but because they are based on buffered
measurements, they lag real time by some amount depending on the latency of the data link. If the remote receiver
has not been enabled to accept RTK differential data, or is not actually receiving data leading to a valid solution,
this will be reflected by the code shown in field #16 (RTK status) and #17 (position type).
The data in the logs will change only when a reference observation (RTCM Type 59 or the corresponding RTCA
Type 7) changes. If the log is being output at a fixed rate and the differential data is interrupted, then the RTKA/B
logs will continue to be output at the same rate but the position and time will not change.
A good message trigger for this log is "ONCHANGED". Then, only positions related to unique reference station
messages will be produced, and the existence of this log will indicate a successful link to the reference station.
RTKA
Structure:
$RTKA
lat
week seconds #sv
#high L1L2 #high
datum ID
lon
hgt undulation
lat σ
lon σ
hgt σ soln status rtk status
posn type dyn mode
stn ID
*xx
[CR][LF]
Field # Field type
Data Description
Example
$RTKA
1
2
3
4
5
$RTKA
week
Log header
GPS week number
872
seconds
#sv
GPS time into the week (in seconds)
174962.00
Number of matched satellites; may differ from the number in view.
8
7
#high
Number of matched satellites above RTK mask angle; observations from satellites
below mask are heavily de-weighted
6
7
L1L2 #high
lat
Number of matched satellites above RTK mask angle with both L1 and L2 available
7
Latitude of position in current datum, in decimal fraction format. A negative sign
implies South latitude
51.11358039754
8
lon
Longitude of position in current datum, in decimal fraction format. A negative sign -114.04358003164
implies West longitude
9
hgt
Height of position in current datum, in meters above mean sea level
1059.4105
-16.2617
10
undulation
Geoidal separation, in meters, where positive is above ellipsoid and negative is
below ellipsoid
11
12
13
14
15
16
17
18
19
20
21
datum ID
lat σ
lon σ
Standard deviation of latitude solution element, in meters
Standard deviation of longitude solution element, in meters
Standard deviation of height solution element, in meters
61
0.0036
0.0039
0.0066
hgt σ
soln status
rtk status
posn type
dyn mode
stn ID
0
Dynamics mode (0= static, 1= kinematic)
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Checksum
0
119
*33
*xx
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$RTKA,872,174962.00,8,7,7,51.11358039754,-114.04358003164,1059.4105,
-16.2617,61,0.0036,0.0039,0.0066,0,0,4,0,119*33[CR][LF]
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Logs summary
RTKB
Format:
Message ID = 61
Data
Message byte count = 116
Field #
Bytes Format
Units
Offset
0
1
Sync
3
1
4
4
4
8
4
4
4
char
(header) Checksum
Message ID
char
3
integer
integer
integer
double
integer
integer
integer
4
Message byte count
Week number
GPS time into the week
Number of matched satellites (00-12)
8
2
3
4
5
6
weeks
12
16
24
28
32
seconds
Number of matched satellites above RTK mask angle
Number of matched satellites above RTK mask angle with both L1 and
L2 available
7
Latitude
8
8
8
8
4
8
8
8
4
4
4
4
4
double
double
double
double
integer
double
double
double
integer
integer
integer
integer
integer
degrees
degrees
meters
meters
36
8
Longitude
44
9
Height above mean sea level
Undulation
52
10
11
12
13
14
15
16
17
18
19
60
Datum ID
68
Standard deviation of latitude
Standard deviation of longitude
Standard deviation of height
Solution status
meters
meters
meters
72
80
88
96
RTK status
100
104
108
112
Position type
Dynamics mode
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 -
15179385)
206
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Logs summary
RTKOA/B
RTK Solution Parameters
RTK
This is the “RTK output” log, and it contains miscellaneous information regarding the RTK solution. It is based on
the matched update. Note that the length of the log messages will vary depending on the number of matched
satellites in the solution, a quantity represented by #sv in the field numbers.
RTKOA
Structure:
$RTKOA week
sec
status #sat #high L1L2 #high #sv
σxx
dyn
σzx
search
combn
σzz
σxy
σxz
σyx
σ∆x
σyy
σ∆y
σyz
σ∆z
σzy
∆x
∆y
∆z
rsrv
rsrv
ref id #res
res
sat id amb
:
sat id amb
res
*xx
Field#
[CR][LF]
Field type
$RTKOA
week
Data Description
Example
1
2
3
4
5
6
Log header
$RTKOA
929
GPS week number
sec
GPS time into the week (in seconds)
237639.00
status
#sat
1
8
8
Total number of matched satellites available to both receivers
#high
Number of matched satellites above RTK mask angle;
observations from satellites below mask are heavily
deweighted
7
8
L1L2 #high
#sv
Number of matched satellites above RTK mask angle with
both L1 and L2 available
8
8
Number of matched satellites in solution; may differ from the
number in view.
9
dyn
Dynamics mode (0=static, 1=kinematic)
0
4
1
10
search
combn
[σ]
Number of possible lane combinations remaining
The σ ,σ ,σ ,σ ,σ ,σ ,σ ,σ , and σ components,
11
12-20
0.000006136,0.000003797,-0.000003287,
0.000003797,0.000013211,-0.000007043,
-0.000006287,-0.000007043,0.000018575
xx xy xz yx yy yz zx zy
2
zz
in (meters) , of the ECEF position covariance matrix (3 x 3)
21-23
24-26
∆x,∆y,∆z
ECEF x.y,z of baseline from float solution in meters
3.2209,-3.0537,-1.2024
σ ,σ ,σ
x,y,z standard deviations of float solution baseline in meters 0.0183,0.0138,0.0124
∆x ∆y ∆z
27
28
29
30
31
32
33
rsrv
Reserved for future use
Reserved for future use
Reference PRN
0
rsrv
0.0000
ref id
#res
sat id
amb
res
1
Number of residual sets to follow
PRN number
7
21
Residual in metres
6
-0.001199
...
...
...
...
...
...
Next PRN number, amb, res
...
Last PRN number, amb, res
variable
variable
*xx
Checksum
*60
[CR][LF]
Sentence terminator
[CR][LF]
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Logs summary
Example:
$RTKOA,929,237639.00,1,8,8,8,8,0,4,1,0.000006136,0.000003797,
-0.000006287,0.000003797,0.000013211,-0.000007043,-0.000006287,
-0.000007043,0.000018575,3.2209,-3.0537,
-1.2024,0.0183,0.0138,0.0124,0,0.0000,1,7,
21,6,-0.001199,23,6,0.005461,31,6,0.009608,9,6,0.001963,
15,6,0.000208,29,6,-0.005643,25,6,-0.004366*60[CR][LF]
RTKOB
Format:
Message ID = 62
Message byte count = 196 + (#res)*16
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
4
4
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
integer
double
integer
integer
Message byte count
GPS week number
GPS time into the week
2
3
4
5
weeks
s
12
16
24
28
Total number of matched satellites available to both
receivers.
6
7
Number of matched satellites above RTK mask
angle
4
4
integer
integer
32
36
Number of matched satellites above RTK mask
angle with both L1 and L2 available
8
Number of matched satellites in solution
Dynamics mode (0=static, 1=kinematic)
Number of possible lane combinations remaining
Position covariance matrix
4
4
4
4
integer
integer
integer
integer
double
40
44
48
52
56
9
10
11
12-20
2
72
m
21-23
24-26
27
Baseline in ECEF x,y,z from float filter
Standard deviations of x,y,z from float filter
Reserved for future use
24
24
4
double
double
integer
double
integer
integer
integer
integer
double
m
m
128
152
176
180
188
192
196
28
Reserved for future use
8
29
Reference PRN
4
30
Number of residual sets to follow
PRN number
4
31
4
32
Residual
4
33
8
m
34
Next PRN offset = 196 + (#res)*16
208
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Logs summary
Table D-8 Ambiguity Types
Ambiguity Type
Definition
L1 only floating
0
1
Wide lane fixed integer
Reserved
2
3
Narrow lane floating
Iono–free floating
Reserved
4
5
6
Narrow lane fixed integer
Iono–free fixed discrete
L1 only fixed integer
Reserved
7
8
9
10
Undefined type
Higher numbers are reserved for future use
Table D-9 Searcher Status
Definition
Searcher Status
0
1
2
3
4
No search requested
Searcher buffering measurements
Currently searching
Search decision made
Hand-off to L1 and L2 complete
Higher numbers are reserved for future use
Table D-10 RTK Status
Definition
RTK Status
1
2
Good narrowlane solution
Good widelane solution
4
Good L1/L2 converged float solution
Good L1/L2 unconverged float solution
Good L1 converged solution
Good L1 unconverged solution
Reserved for future use
Insufficient observations
Variance exceeds limit
Residuals exceed limit
Delta position too large
Negative variance
8
16
32
64
128
256
512
1024
2048
4096
8192
Undefined
RTK initialize
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Logs summary
RVSA/B
Receiver Status
This log conveys various status parameters of the receiver system. If the system is a multiple-GPSCard unit with
a master card, certain parameters are repeated for each individual GPSCard. If the system is composed of only one
GPSCard, then only the parameters for that unit are listed. Together, the RVSA/B and VERA/B logs supersede
the RCSA/B logs.
Note that the number of satellite channels (the number of satellites the receiver is capable of tracking) is not
necessarily the same as the number of signal channels. This is because one L1/L2 satellite channel requires two
signal channels. Therefore the 12-channel MiLLennium GPSCard will report 24 signal channels in this field. This
number represents the maximum number of channels reporting information in logs such as ETSA/B and RGEA/
B/D.
RVSA
Structure:
$RVSA week seconds sat_chan
sig_chan num reserve
idle status
:
idle status
*xx [CR][LF]
Field #
Field type
$RVSA
Data Description
Example
1
2
3
4
5
6
7
8
9
Log header
$RVSA
week
GPS week number
847
seconds
sat_chan
sig_chan
num
GPS seconds into the week.
Number of satellite channels
Number of signal channels
318923.00
12
24
1
Number of cards
reserve
idle
Reserved field
First GPSCard: CPU idle time (percent)
16.00
status
...
...
...
000B00FF
...
...
...
Next GPSCard: CPU idle time & self-test status
...
Last GPSCard: CPU idle time & self-test status
variable
variable
*xx
Checksum
*42
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$RVSA,847,318923.00,12,24,1,,16.00,000B00FF*42[CR][LF]
210
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Logs summary
RVSB
Format:
Message ID = 56
Message byte count = 28 + (8 x number of cards)
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
0
(header)
Checksum
1
4
4
4
8
1
1
1
1
4
4
char
3
Message ID
integer
integer
integer
double
char
4
Message byte count
Week number
8
2
3
4
5
6
7
8
9
weeks
12
Seconds of week
Number of satellite channels
Number of signal channels
Number of cards
Reserved
seconds 16
24
25
26
27
28
32
char
char
byte
CPU idle time, percent
Self-test status
float
integer
8 & 9 are repeated
for each card
Next Card offset = 28 + (8 x card number)
NOTE: For Field 9, self-test bits 2, 3, 4, 6, & 7 are set only once (when the GPSCard is first powered up). All
other bits are set by internal test processes each time the RVSB log is output.
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Logs summary
SATA/B
Satellite Specific Data
This log provides satellite specific data for satellites actually being tracked. The record length is variable and
depends on the number of satellites.
Each satellite being tracked has a reject code indicating whether it is used in the solution, or the reason for its
rejection from the solution. The reject value of 0 indicates the observation is being used in the position solution.
Values of 1 through 11 indicate the observation has been rejected for the reasons specified in Table D-11. A range
reject code of 8 only occurs when operating in differential mode and an interruption of corrections has occurred or
the DGPSTIMEOUT has been exceeded.
SATA
Structure:
# obs
$SATA
prn
:
week
seconds sol status
elevation
azimuth
residual reject code
elevation
prn
*xx
azimuth
residual reject code
[CR][LF]
Field #
Field type
$SATA
Data Description
Example
1
2
3
4
5
6
7
Log header
$SATA
week
GPS week number
637
seconds
sol status
# obs
GPS seconds into the week
513902.00
Solution status as listed in Table D-1
Number of satellite observations with information to follow:
Satellite PRN number (1-32)
0
7
prn
18
azimuth
Satellite azimuth from user position with respect to True North, in
degrees
168.92
8
elevation
residual
Satellite elevation from user position with respect to the horizon, in 5.52
degrees
9
Satellite range residual from position solution for each satellite, in
metres
9.582
10
reject code
Indicatesthat the range is beingusedin the solution (code 0) or that
it was rejected (code 1-11), as shown in Table D-11
0
...
...
...
...
...
...
Next PRN number, azimuth, elevation, residual, reject code
...
Last PRN number, azimuth, elevation, residual, reject code
variable
variable
*xx
Checksum
*1F
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$SATA,637,513902.00,0,7,18,168.92,5.52,9.582,0,6,308.12,55.48,0.737,0,
15,110.36,5.87,16.010,0,11,49.63,40.29,-0.391,0,
2,250.05,58.89,-12.153,0,16,258.55,8.19,-20.237,0,
19,118.10,49.46,-14.803,0*1F[CR][LF]
212
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Logs summary
SATB
Format:
Message ID =12 Message byte count = 32 + (obs*32)
Data Bytes Format
Field #
Units
Offset
1
Sync
3
1
4
4
4
8
4
4
char
char
0
(header)
Checksum
3
Message ID
integer
integer
integer
double
integer
integer
4
Message byte count
Week number
Seconds of week
Solution status
8
2
3
4
5
weeks
12
16
24
28
seconds
Number of
observations (obs)
6
PRN
4
8
8
8
4
integer
double
double
double
integer
32
36
44
52
60
7
Azimuth
Elevation
Residual
Reject Code
degrees
degrees
metres
8
9
10
11...
Next PRN offset = 32 + (obs*32) where obs varies form 0 to (obs-1)
Table D-11 GPSCard Range Reject Codes
Description
Value
0
Observations are good
1
Bad satellite health is indicated by ephemeris data
2
Old ephemeris due to data not being updated during last 3 hours
Eccentric anomaly error during computation of the satellite’s position
True anomaly error during computation of the satellite’s position
Satellite coordinate error during computation of the satellite’s position
Elevation error due to the satellite being below the cutoff angle
Misclosure too large due to excessive gap between estimated and actual positions
No differential correction is available for this particular satellite
Ephemeris data for this satellite has not yet been received
Invalid IODE due to mismatch between differential stations
Locked Out: satellite is excluded by user (LOCKOUT command)
Low Power: satellite rejected due to low signal/noise ratio
L2 measurements are not currently used in the filter
3
4
5
6
7
8
9
10
11
12
13
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Logs summary
SBTA/B
SATELLITE BROADCAST DATA: RAW SYMBOLS
This message contains the satellite broadcast data in raw symbols before FEC decoding or any other processing.
An individual message is sent for each PRN being tracked. For a given satellite, the message number increments
by one each time a new message is generated. This data matches the RBTA/B data if the message numbers are
equal. The data must be logged with the ’onnew’trigger activated to prevent loss of data.
SBTA
Structure:
$SBTA week
raw symbols
seconds
prn cstatus
message # # of symbols
*xx [CR][LF]
Field #
Field type
Data Description
Example
1
2
3
4
5
6
7
$SBTA
week
Log header
$SBTA
883
GPS week number
seconds
prn
GPS seconds into the week
PRN of satellite from which data originated
Channel Tracking Status
Message sequence number
413908.000
120
cstatus
message #
# of symbols
80812F14
119300
Number of symbols transmitted in the message. At present,
always equals 256 symbols.
256
8
raw symbols
256 symbols compressed into a 128 bytes, i.e. 4 bits/symbol. EE33EEEE33333E33EE33EEEE33
Hence, 256 hex characters are output. If FEC decoding is 333E33EE33EEEE33333E33EE33E
enabled, soft symbols are output with values ranging from E EEE33333EEEE3333EEE33E33E3
to 3 where 3’s represent binary 1 and E’s represent binary 0 EE33EEE3EEEE33EE3E3EEEEEE
output.
EEEEEEEE3333EEE33EEEEE33E
E3EEE3E3EE3EE33EEE33E333EE
3333E3E3333E33E3333EEEEE333
EE3E3333EE3EE3EE33EE3EE3EE
3E33E33E3EEE33333E3333E33E3
E333E3E33333E3EEE3E3E
9
*xx
Checksum
*4C
10
[CR][LF]
Sentence terminator
[CR][LF]
SBTB
Format:
Message ID = 53
Data
Message byte count = 168
Bytes Format
char
Field #
Units
Offset
1
Sync
3
0
(header)
Checksum
1
char
3
Message ID
4
integer
integer
integer
double
integer
integer
integer
integer
char
4
Message byte count
Week number
Seconds of week
PRN number
Channel Status
Message #
4
bytes
8
2
3
4
5
6
7
8
4
weeks
seconds
1-999
n/a
12
16
24
28
32
36
40
8
4
4
4
n/a
# of Symbols
Raw Symbols
4
n/a
128
n/a
214
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D
Logs summary
SPHA/B Speed and Direction Over Ground
This log provides the actual speed and direction of motion of the GPSCard antenna over ground, at the time of
measurement, and is updated up to 10 times per second. It should be noted that the GPSCard does not determine
the direction a vessel, craft, or vehicle is pointed (heading), but rather the direction of motion of the GPS antenna
relative to ground.
SPHA
Structure:
$SPHA week seconds
hor spd trk gnd
*xx [CR][LF]
Data Description
sol status
Field type
vert spd
Field #
Example
$SPHA
1
2
3
4
5
$SPHA
week
Log header
GPS week number
640
seconds
hor spd
trk gnd
GPS seconds into the week
333111.00
0.438
Horizontal speed over ground, in meters per second
Actual direction of motion over ground (track over ground) 325.034
with respect to True North, in degrees
6
vert spd
Vertical speed, in metres per second, where positive
values indicate increasing altitude (up) and negative
values indicate decreasing altitude (down)
2.141
7
8
9
sol status
*xx
Solution status as listed in Table D-1
Checksum
0
*02
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$SPHA,640,333111.00,0.438,325.034,2.141,0*02[CR][LF]
SPHB
Format:
Message ID = 06
Message byte count = 52
Bytes Format
char
Field #
1
Data
Units
Offset
Sync
3
1
4
4
4
8
8
8
8
4
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
integer
double
double
double
double
integer
Message byte count
Week number
2
3
4
5
6
7
weeks
seconds
12
16
24
32
40
48
Seconds of week
Horizontal speed
Track over ground (TOG)
Vertical speed
metres per second
degrees
metres per second
Solution status
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D
Logs summary
SVDA/B SV Position in ECEF XYZ Coordinates with Corrections
When combined with a RGEA/B/D log, this data set contains all of the decoded satellite information necessary to
compute the solution: satellite coordinates (ECEF WGS84), satellite clock correction, ionospheric corrections (from
broadcast model), tropospheric corrections (Hopfield model), decoded differential correction used and range
weight standard deviation. The corrections are to be added to the pseudoranges. Only those satellites that are
SVDA
Structure:
week seconds
$SVDA
prn
:
rec clk err # obs
x
x
y
z
clk corr
ion corr trop corr diff corr rng std
prn
*xx
y
z
clk corr
ion corr trop corr diff corr rng std
[CR][LF]
Field #
Field type
$SVDA
Data Description
Example
$SVDA
1
2
3
Log header
week
GPS week number
766
seconds
GPS seconds into the week (receiver time, not corrected for clock
error, CLOCKADJUST enabled)
143860.00
4
rec clk err
# obs
prn
Solved receiver clock error (metres)
Number of satellite observations to follow
Satellite PRN number (1-32)
-4.062
5
7
6
20
7
x
Satellite x coordinate (metres)
-15044774.225
-9666598.520
19499537.398
6676.013
-1.657
8
y
Satellite y coordinate (metres)
9
z
Satellite z coordinate (metres)
10
11
12
13
14
clk corr
ion corr
trop corr
diff corr
rng std
Satellite clock correction (metres)
Ionospheric correction (metres)
Tropospheric correction (metres)
Decoded differential correction used (metres)
Range weight standard deviation (metres)
-2.662
16.975
0.674
...
...
...
...
...
...
Next PRN number, x, y, z, clk corr, ion corr, trop corr, diff corr, mg std
...
Last PRN number, x, y, z, clk corr, ion corr, trop corr, diff corr, mg std
variable
variable
*xx
Checksum
*23
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$SVDA,766,143860.00,-4.062,7,
20,-15044774.225,-9666598.520,19499537.398,6676.013,-1.657,-2.662,16.975,0.674
5,-10683387.874,-21566845.644,11221810.349,18322.228,-1.747,-2.819,-8.864,0.790,
6,-20659074.698,-28381.667,16897664619,57962.693,-2.543,4.401,-37.490,1.203,
16,142876.148,-26411452.927,2795075.561,-22644.136,-2.733,-4.904,7.701,1.259,
24,-852160.876,-16138149.057,21257323.813,229594.682,-1.545,-2.451,32.178,0.420,
25,-12349609.643,11102877.199,20644151.935,-4313.339,-3.584,-8.579,
-42.813,1.370,
..,
4,14209626.440,-9259502.647,20544348.215,12811.399,-2.675,-4.741,-10.778,1.239
*23[CR][LF]
216
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D
Logs summary
SVDB
Format:
Message ID = 36
Message byte count = 36 +(obs*68)
Field #
1
Data
Bytes
Format
char
Units
Offset
0
Sync
3
1
4
4
4
8
8
4
4
8
8
8
8
8
8
8
8
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
double
integer
integer
double
double
double
double
double
double
double
double
4
Message byte count
8
2
Week number
weeks
12
16
24
32
36
40
48
56
64
72
80
88
96
3
Time in seconds
seconds
metres
4
Receiver clock error
5
Number of observations to follow (obs)
Satellite PRN number
x coordinate of satellite
y coordinate of satellite
z coordinate of satellite
Satellite clock correction
Ionospheric correction
Tropospheric correction
Decoded differential correction used
Range weight standard deviation
6
7
metres
metres
metres
metres
metres
metres
metres
metres
8
9
10
11
12
13
14
15...
Next PRN offset = 36 + (obs 68) where obs varies from 0 to (obs-1)
*
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D
Logs summary
TM1A/B
Time of 1PPS
This log provides the time of the GPSCard 1PPS, normally high, active low pulse (1 millisecond), where falling
edge is reference, in GPS week number and seconds into the week. The TM1A/B log follows a 1PPS pulse. It also
includes the receiver clock offset, the standard deviation of the receiver clock offset and clock model status. This
log will output at a maximum rate of 1 Hz.
TM1A
Structure:
$TM1A week seconds
utc offset cm status
Field type
offset offset std
*xx
[CR][LF]
Field #
Data Description
Example
$TM1A
1
2
3
$TM1A
week
Log header
GPS week number
794
seconds
GPS seconds into the week at the epoch coincident with the 1PPS
output strobe (receiver time)
414634.99999996
6
4
offset
Receiver clock offset, in seconds. A positive offset implies that the
receiver clock is ahead of GPS Time. To derive GPS time, use the
following formula:
-0.000000078
GPS time = receiver time - (offset)
5
6
offset std
utc offset
Standard deviation of receiver clock offset, in seconds
0.000000021
This field represents the offset of GPS time from UTC time, computed -9.999999998
using almanac parameters. To reconstruct UTC time, algebraically
subtract this correction from field 3 above (GPS seconds).
UTC time = GPS time + (utc offset)
7
cm status
Receiver Clock Model Status where 0 is valid and values from -20 to -1
imply that the model is in the process of stabilization
0
8
9
*xx
Checksum
*57
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$TM1A,794,414634.999999966,-0.000000078,0.000000021,-9.999999998,0*57[CR][LF]
TM1B
Format:
Message ID = 03
Message byte count = 52
Bytes Format Units
char
Field #
Data
Offset
1
Sync
3
1
4
4
4
8
8
8
8
4
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
integer
double
double
double
double
integer
Message byte count
Week number
Seconds of week
Clock offset
2
3
4
5
6
7
weeks
12
16
24
32
40
48
seconds
seconds
seconds
seconds
Stddev clock offset
UTC offset
Clock model status
218
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D
Logs summary
VERA/B Receiver Hardware and Software Version Numbers
This log contains the current hardware type and software version number for the GPSCard. Together with the
RVSA/B log, it supersedes the RCSA/B log.
VERA
Structure:
$VERA week
seconds
version
*xx [CR][LF]
Field # Field type
Data Description
Example
1
$VERA
week
Log header
$VERA
853
2
3
4
GPS week number
seconds
version
GPS seconds into the week.
401364.50
GPSCard hardware type and software version number
OEM-3MILLENSTDCGL96170069
HW 3-1 SW 4.42/2.03 May 14/96
5
6
*xx
Checksum
*2B
[CR][LF]
Sentence terminator
[CR][LF]
Example:
$VERA,853,401364.50,OEM-3 MILLENSTD CGL96170069 HW 3-1 SW 4.42/2.03 May 14/
96*2B[CR][LF]
VERB
Format:
Message ID = 58
Message byte count = 104
Field #
Data
Bytes
Format
char
Units
Offset
1
Sync
3
1
4
4
4
8
0
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
char
4
Message byte count
Week number
Time into week
Version numbers
8
2
3
4
weeks
s
12
16
24
80
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D
Logs summary
VLHA/B Velocity, Latency, and Direction over Ground
This log is similar to the SPHA/B message. As in the SPHA/B messages the actual speed and direction of the
GPSCard antenna over ground is provided. The VLHA/B differs in that it provides a measure of the latency in the
velocity time tag and a new velocity status word which gives the user more velocity quality information. The
velocity status indicates varying degrees of velocity quality. To ensure healthy velocity, the position sol-status
must also be checked. If the sol-status is non-zero, the velocity will likely be invalid. Also, it includes the age of
the differential corrections used in the velocity computation. It should be noted that the GPSCard does not
determine the direction a vessel, craft, or vehicle is pointed (heading), but rather the direction of motion of the GPS
antenna relative to ground.
VLHA
Structure:
$VLHA week seconds
latency age
hor spd trk gnd
*xx [CR][LF]
vert spd
sol status vel status
Field #
Field type
$VLHA
Data Description
Example
$VLHA
1
2
3
4
Log header
week
GPS week number
GPS seconds into the week
640
seconds
333111.00
1
A measure of the latency in the velocity time tag in seconds. It 0.250
should be subtracted from the time to give improved results.
latency
5
6
7
age
Age of Differential GPS data in seconds
3.500
0.438
hor spd
trk gnd
Horizontal speed over ground, in metres per second
Actual direction of motion over ground (track over ground) with 325.034
respect to True North, in degrees
8
vert spd
Vertical speed, in metres per second, where positive values
indicate increasing altitude (up) and negative values indicate
decreasing altitude (down)
2.141
9
sol status
vel status
*xx
Solution status as listed in Table D-1
Velocity status as listed in Table D-12
Checksum
0
10
11
12
0
*02
[CR][LF]
Sentence terminator
[CR][LF]
1
Velocity Latency
The velocity is computed using Doppler values derived from differences in consecutive carrier phase
measurements. As such, it is an average velocity based on the time difference between successive
position computations and not an instantaneous velocity at the SPHA/B time tag. Under normal operation
the position’s coordinates are updated at a rate of two times per second. The velocity latency compared
to this time tag will normally be 1/2 the time between position fixes. The default filter rate is 2 Hz, so
this latency is typically 0.25 second, but if, for example, the POSA records were to be logged ontime 0.2,
then the velocity latency would be one half of 0.2, or 0.1 second. The latency can be reduced further by
the user requesting the POSA/B, the SPHA/B, or the VLHA/B messages at rates higher than 2 Hz. For
example, a rate of 10 Hz will reduce the velocity latency to 1/20 of a second. For integration purposes,
the velocity latency should be applied to the record time tag.
Example:
$VLHA,640,333111.00,0.250,3.500,0.438,325.034,2.141,0,0*02[CR][LF]
220
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D
Logs summary
VLHB
Format:
Message ID = 34
Message byte count = 72
Field #
1
Data
Bytes
Format
char
Units
Offset
Sync
3
1
4
4
4
8
8
8
8
8
8
4
4
0
(header)
Checksum
char
3
Message ID
integer
integer
integer
double
double
double
double
double
double
integer
integer
4
Message byte count
Week number
Seconds of week
Latency
8
2
3
4
5
6
7
8
9
10
weeks
12
16
24
32
40
48
56
64
68
seconds
metres per second
seconds
Age
Horizontal speed
Track over ground (TOG)
Vertical speed
Solution status
Velocity status
metres per second
degrees
metres per second
Table D-12 GPSCard Velocity Status
Description
Value
0
1
2
3
4
5
Velocity computed from differentially corrected carrier phase data
Velocity computed from differentially corrected Doppler data
Old velocity from differentially corrected phase or Doppler (higher latency)
Velocity from single point computations
Old velocity from single point computations (higher latency)
Invalid velocity
Higher values reserved for future use
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D
Logs summary
WALA/B WAAS Almanac
WAAS
Structure:
$WALA
prn
week
seconds
health
pos Z
WAAS week WAAS seconds
data ID
pos Y
vel Y
pos X
vel X
vel Z
Field #
Field type
Data Description
Example
1
$WALA
Log header
$WALA
2
week
GPS week number
981
3
seconds
WAAS week
WAAS seconds
prn
GPS seconds into the week
447490.88
981
4
WAAS week number
5
WAAS seconds into the week at time of application
WAAS GEO satellite PRN number
447360
6
122
7
data ID
health
Version of WAAS signal specification, see Table D-14
Health and status of the WAAS GEO satellite, see Table D-13
Position x coordinate of WAAS GEO satellite at WAAS seconds (Field #5)
Position y coordinate of WAAS GEO satellite at WAAS seconds (Field #5)
Position z coordinate of WAAS GEO satellite at WAAS seconds (Field #5)
Velocity x coordinate of WAAS GEO satellite
Velocity y coordinate of WAAS GEO satellite
Velocity z coordinate of WAAS GEO satellite
Checksum
0
8
0
9
pos X
2.5789400E+007
-3.5479600E+007
2.60000000E+004
0.00000000E+000
0.00000000E+000
0.00000000E+000
*32
10
11
12
13
14
15
16
pos Y
pos Z
vel X
vel Y
vel Z
*xx
[CR][LF]
Sentence terminator
[CR] [LF]
*Example:
$WALA,981,447490.88,981,447360,122,0,0,2.57894000E+007,-
3.5479600E+007,2.60000000E+004,0.00000000E+000,0.00000000E+000,0.00000000E+000*32 [CR][LF]
222
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D
Logs summary
WALB
Format:
Message ID = 81
Message byte count = 92
Bytes Format
Field #
1
Data
Units
Offset
Sync
3
1
4
4
4
8
4
4
4
4
4
8
8
8
8
8
8
char
0
3
4
8
(header)
Checksum
char
Message ID
integer
integer
ulong
Message byte count
2
Week number
weeks
12
16
24
28
32
36
40
44
52
60
68
76
84
3
Seconds of week
double
integer
integer
integer
integer
integer
double
double
double
double
double
double
seconds
weeks
4
WAAS week number
5
WAAS seconds of week
seconds
6
WAAS satellite PRN number
WAAS signal specification version
WAAS satellite health
7
8
9
Position x coordinate of WAAS satellite
Position y coordinate of WAAS satellite
Position z coordinate of WAAS satellite
Velocity x coordinate of WAAS satellite
Velocity y coordinate of WAAS satellite
Velocity z coordinate of WAAS satellite
meters
meters
meters
m/s
10
11
12
13
14
m/s
m/s
Table D-13 Health and Status Bits
Bit Number*
Description
Ranging
Range Values
0 = On 1 = Off
0
1
Corrections
0 = On 1 = Off
2
Broadcast integrity
Reserved
0 = On 1 = Off
3
-
4-7
Service Provider ID
-
*Note:
Read the binary output from the Health field from right to left. The first bit to the right, the least significant bit,
is bit 0 and so on to the left.
Table D-14 Data ID Type
Data ID
Type (Service Provider)
WAAS (Wide Area Augmentation System)
0
1
EGNOS (European Geostationary Navigation Overlay Service)
MSAS (Multi-Functional Transport Satellite (MTSAT) based Augmentation System)
Reserved
2
3-15
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D
Logs summary
WRCA/B Wide Band Range Correction (Grouped Format)
This message contains the wide band range correction data. A correction is generated for each PRN being tracked
and these group together into a single log. Internally, the correction for each satellite is updated asynchronously
at a 1 Hz rate. Therefore, logging this message at a rate higher than 1 Hz will result in duplicate data being output.
Each range correction is statistically independent and is derived from the previous 1 second of data.
WRCA
Structure:
$WRCA
week
seconds
# obs
prn ch-tr-status tr-bandwidth
wide band correction
wide band correction
Data Description
:
prn ch-tr-status tr-bandwidth
*xx [CR][LF]
Field #
Field type
$WRCA
Example
1
2
3
4
5
6
Log header
$WRCA
637
week
GPS week number
seconds
# obs
GPS seconds into the week
513902.00
7
Number of satellite observations with information to follow:
Satellite PRN number
prn
18
ch-tr-status
Channel Tracking Status: Hexadecimal number indicating phase lock, channel E04
number and channel tracking state as shown in Table D-7.
7
8
tr-bandwidth
DLL tracking loop bandwidth in Hz
Wide band range correction in metres
0.050
wide band correction
1.323
...
...
...
...
...
...
Next PRN number, ch-tr-status, tr-bandwidth, wide band correction
...
Last PRN number, ch-tr-status, tr-bandwidth, wide band correction
variable
variable
*xx
Checksum
*1F
[CR][LF]
Sentence terminator
[CR][LF]
WRCB
Format:
Message ID = 67
Message byte count = 28 + (obs*16)
Bytes Format
char
Field #
Data
Units
Offset
1
Sync
3
0
(header)
Checksum
1
4
4
4
8
4
4
4
4
4
char
3
Message ID
integer
integer
integer
double
integer
integer
-
4
Message byte count
Week number
bytes
8
2
weeks
seconds
12
16
24
28
32
36
40
3
Seconds of week
4
Number of observations (obs)
PRN
5
6
Channel tracking status
DLL tracking loop bandwidth
Wide Band Range Correction
Next PRN offset = 28 + (obs*16)
-
7
float
Hz
8
float
metres
9...
224
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E
Comparison Of RT-2 And RT-20
E
COMPARISON OF RT-2 AND RT-20
E
COMPARISON OF RT-2 AND RT-20
E.1 RT-2 & RT-20 PERFORMANCE
RT-2 and RT-20 are real-time kinematic software products developed by NovAtel. They can only be used in
conjunction with NovAtel GPS receivers. A quick comparison of RT-2 and RT-20 is shown in Table E-1:
Table E-1 Comparison of RT-2 and RT-20
RT-2
RT-20
GPS Frequencies Utilized
Nominal Accuracy
Lane Searching
L1 & L2
L1
2 cm (CEP)
20 cm (CEP)
None
Wide lane and narrow lane
NovAtel’s RTK software algorithms utilize both carrier and code phase measurements; thus, the solutions are
robust, reliable, accurate and rapid. While both RT-20 and RT-2 operate along similar principles, RT-2 achieves
its extra accuracy and precision due to its being able to utilize dual-frequency measurements. Dual-frequency GPS
receivers have two main advantages over their single-frequency counterparts when running RTK software:
1. resolution of cycle ambiguity is possible due to the use of wide lane searching
2. longer baselines are possible due to the removal of ionospheric errors
Depending on the transmitting and receiving receivers, various levels of accuracy can be obtained. Please refer to
the particular accuracy as shown in Table E-2.
Table E-2 RTK Messages Vs. Accuracy
Transmitting (Reference)
GPSCard transmitting RTCA
Receiving (Remote)
RT-2 receiver
Accuracy Expected
2 centimetre CEP
(i.e. RTCAOBS and RTCAREF)
RT-20 receiver
RT-2 receiver
20 centimetre CEP
20 centimetre CEP
GPSCard transmitting RTCM type 3 and 59
RT-20 receiver
RT-2 receiver
20 centimetre CEP
1 metre SEP
GPSCard transmitting RTCM or RTCA type 1
RT-20 receiver
RT-2 receiver
1 metre SEP
1
20 centimetre CEP
GPSCard transmitting RTCM type 18 and 19 with type 3
RT-20 receiver
20 centimetre CEP
1
The RTCM1819 message can only be transmitted and received by MiLLennium GPSCards
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Comparison Of RT-2 And RT-20
RT-2 Performance
The RT-2 software provides the accuracies shown in Table E-3 & Figure E-1 (static mode) and Table E-4 &
Figure E-2 (kinematic mode) for “typical” multipath, ionospheric, tropospheric, and ephemeris errors, where
“typical” is described as follows:
•
A typical multipath environment would provide no carrier-phase double-difference multipath errors
greater than 2 cm or pseudorange double-difference multipath errors greater than 2 m on satellites at 11°
elevation or greater. For environments where there is greater multipath, please consult NovAtel Customer
Service.
•
Typical unmodeled ionospheric, tropospheric and ephemeris errors must be within 2σ of their average
values, at a given elevation angle and baseline length. It is assumed that the tropospheric correction is
computed with standard atmospheric parameters. All performance specifications assume that at least 6
satellites above the mask angle (varies between 11 and 14 degrees) are being tracked on both L1 and L2.
In Tables E-3 and E-4, accuracy values refer to horizontal RMS error, and are based on matched positions. There
are no data delays for a matched log and therefore no need to add anything. The level of position accuracy at any
time will be reflected in the standard deviations output with the position.
Table E-3 RT-2 Performance: Static Mode
Baseline
length
Time since L2 lock-on with at least Horizontal accuracy at
Runs meeting the stated
accuracy at the stated time
6 satellites above mask angle
the stated time
< 10 km
70 seconds + 1.5 sec/km
5 minutes
2 cm + 0.5 ppm
75.0%
75.0%
66.7%
66.7%
66.7%
66.7%
< 10 km
< 15 km
< 25 km
< 35 km
< 35 km
1 cm + 1 ppm
5 cm
4 minutes
7 minutes
7 cm
10 minutes
35 cm
30 minutes
25 cm
Table E-4 RT-2 Performance: Kinematic Mode
Baseline
length
Time since L2 lock-on with at least Horizontal accuracy at
Runs meeting the stated
accuracy at the stated time
6 satellites above mask angle
the stated time
< 10 km
120 seconds + 1.5 sec/km
8 minutes
2 cm + 0.5 ppm
75.0%
66.7%
66.7%
66.7%
66.7%
< 15 km
< 25 km
< 35 km
< 35 km
8 cm
14 minutes
10 cm
40 cm
25 cm
20 minutes
60 minutes
PRTK logs contain some error due to predictions from base station observations. The expected error of a PRTK
log will be that of the corresponding RTK log plus the appropriate error from Table E-5.
Table E-5 RT-2 Degradation With Respect To Data Delay ➀
Data Delay (sec)
Distance (km)
Accuracy (CEP)
0 - 2
2 - 7
7 - 30
>30
1
1
1
1
+1 cm/sec
+2 cm/sec
+5 cm/sec
single point or pseudorange differential positioning ➁
➀
➁
Mode = Static or Kinematic
After 30 seconds reverts to pseudorange positioning (single point or differential depend-
ing on messages previously received from the base station).
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Comparison Of RT-2 And RT-20
Figure E-1 Typical RT-2 Horizontal Convergence - Static Mode
1.4
1.2
1
Baselines
0.1 km
15 km 25 km 50 km
0.8
0.6
0.4
0.2
0
0
300
600
900
1200 1500
1800 2100 2400 2700 3000 3300
Seconds of Convergence
Figure E-2 Typical RT-2 Horizontal Convergence - Kinematic
Mode
1.4
1.2
1
Baselines
0.1 km 15 km 25 km 50 km
0.8
0.6
0.4
0.2
0
0
300
600
900
1200 1500
1800 2100 2400 2700 3000 3300
Seconds of Convergence
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Comparison Of RT-2 And RT-20
For baselines under 30 km long, the RT-2 solution shows two pronounced steps in accuracy convergence; these
correspond to the single-point solution switching to the floating ambiguity solution which in turn switches to the
narrow lane solution. If you were monitoring this using NovAtel’s GPSolution program, the convergence sequence
might look something like what is shown in Figure E-3.
Figure E-4 shows the performance of the RT-2 system running RTCM59 corrections at 1/2 Hz rate.
Figure E-3 RT-2 Accuracy Convergence
Single-point solution
Floating ambiguity solution
Narrow lane solution
Figure E-4 Illustration of RT-2 Steady State Performance
RT-20 Performance
As shown in Table E-6, Figure E-5 and Figure E-6 the RT-20 system provides nominal 20 cm accuracy (CEP)
after 3 minutes of continuous lock in static mode. After an additional period of continuous tracking (from 10 to 20
minutes), the system reaches steady state and position accuracies in the order of 3 to 4 cm are typical. The time to
steady state is about 3 times longer in kinematic mode.
RT-20 double-difference accuracies are based on PDOP < 2 and continuous tracking of at least 5 satellites (6
preferred) at elevations of at least 11.5°.
All accuracy values refer to horizontal RMS error, and are based on low-latency positions. The level of position
accuracy at any time will be reflected in the standard deviations output with the position.
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Comparison Of RT-2 And RT-20
Table E-6 RT-20 Performance
1
Tracking Time (sec)
Data Delay (sec)
Distance (km)
Accuracy (CEP)
Mode
Static
1 - 180
0
0
0
1
1
1
100 to 25 cm
25 to 5 cm
180 - 3000
> 3000
Static
Static
2
5 cm or less
1 - 600
Kinematic
Kinematic
Kinematic
0
0
0
1
1
1
100 to 25 cm
25 to 5 cm
600 - 3000
> 3000
2
5 cm or less
Either
Either
Either
Either
0 - 2
2 - 7
7 - 30
> 30
1
1
1
1
+1 cm/sec
+2 cm/sec
+5 cm/sec
3
pseudorange or single point
Either
Either
Either
0
0
0
0 - 10
10 - 20
20 - 50
+0.5 cm/km
+0.75 cm/km
+1.0 cm/km
1
2
Mode = Static or Kinematic (during initial ambiguity resolution)
The accuracy specifications refer to the PRTKA/B logs which include about 3 cm extrapolation error. RTKA/B logs are
more accurate but have increased latency associated with them.
3
After 30 seconds reverts to pseudorange positioning (single point or differential depending on messages previously
received from the base station).
Figure E-5 Typical RT-20 Convergence - Static Mode
1.4
1.2
Baselines
1
0.1 km 15 km 25 km 50 km
0.8
0.6
0.4
0.2
0
0
300
600
900
1200 1500
1800 2100 2400 2700 3000 3300
Seconds of Convergence
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Comparison Of RT-2 And RT-20
Figure E-6 Typical RT-20 Convergence - Kinematic Mode
1.4
1.2
1
Baselines
0.1 km 15 km 25 km 50 km
0.8
0.6
0.4
0.2
0
0
300
600
900
1200 1500
1800 2100 2400 2700 3000 3300
Seconds of Convergence
Figure E-7 shows the performance of the RT-20 system running with RTCM59 corrections received at a 1/2 Hz rate.
Figure E-7 RT-20 Steady State Performance
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Comparison Of RT-2 And RT-20
E.2 PERFORMANCE CONSIDERATIONS
When referring to the “performance” of RTK software, two factors are introduced:
1. Baseline length: the position estimate becomes less precise as the baseline length increases. Note that the
baseline length is the distance between the phase centres of the two antennas. Identifying the exact position
of your antenna’s phase centre is essential; this information is typically supplied by the antenna’s manufacturer
or vendor.
The RTK software automatically makes the transition between short and longer baselines, but the best
results are obtained for baselines less than 10 km. The following are factors which are related to baseline
length:
•
•
ephemeris errors - these produce typical position errors of 0.75 cm per 10 km of baseline length.
ionospheric effects - the dominant error for single-frequency GPS receivers on baselines exceeding
10 km. Differential ionospheric effects reach their peak at dusk and dawn, being at a minimum during
hours of darkness. Ionospheric effects can be estimated and removed on dual-frequency GPS
receivers, greatly increasing the permissible baseline length, but at the cost of introducing additional
“noise” to the solution. Therefore, this type of compensation is only used in cases where the
ionospheric error is much larger than the noise and multipath error.
•
tropospheric effects - these produce typical position errors of approximately 1 cm per 10 km of base-
line length. This error increases if there is a significant height difference between the reference and
remote stations, as well as if there are significantly different weather conditions between the two sites.
A related issue is that of multipath interference, the dominant error on short differential baselines.
Generally, multipath can be reduced by choosing the antenna’s location with care, and by the use of a
2. Convergence time: the position estimate becomes more accurate and more precise with time. However, con-
vergence time is dependent upon baseline length: while good results are available after a minute or so for
short baselines, the time required increases with baseline length. Convergence time is also affected by the
number of satellites which can be used in the solution: the more satellites, the faster the convergence.
Performance Degradation
The performance will degrade if satellites are lost at the remote or if breaks occur in the differential correction
transmission link. The degradations related to these situations are described in the following paragraphs.
Provided lock is maintained on at least 4 SVs and steady state has been achieved, the only degradation will be the
result of a decrease in the geometrical strength of the observed satellite constellation. If steady state has not been
achieved, then the length of time to ambiguity resolution under only 4-satellite coverage will be increased
significantly.
REMOTE TRACKING LOSS
If less than 4 satellites are maintained, then the RTK filter can not produce a position. When this occurs, the POSA/
B and P20A/B logs will be generated with differential (if RTCM Type 1 messages are transmitted with the Type 59
messages) or single point pseudorange solutions if possible. When the satellites are reacquired, the RTK
DIFFERENTIAL LINK BREAKDOWN
1.
Provided the system is in steady state, and the loss of observation data is for less than 30 seconds, the RTK
positions will degrade according to the divergence of the reference observation extrapolation filters. This
causes a decrease in accuracy of about an order of magnitude per 10 seconds without a reference station
observation, and this degradation is reflected in the standard deviations of the low latency logs. Once the
data link has been re-established, the accuracy will return to normal after several samples have been
received.
2.
If the loss of differential corrections lasts longer than 30 seconds, the RTK filter is reset and all ambiguity
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Comparison Of RT-2 And RT-20
and reference model information is lost. The timeout threshold for RTK differential corrections is 30
seconds, but for Type 1 pseudorange corrections, the timeout is 60 seconds. Therefore, when the RT-20
can no longer function because of this timeout, the pseudorange filter can produce differential positions
for an additional 30 seconds (provided RTCM Type 1 messages were transmitted along with the Type 59
messages) before the system reverts to single point positioning. Furthermore, once the link is re-
established, the pseudorange filter produces an immediate differential position while the RTK filter takes
an additional 14 seconds to generate its positions. The reference models require 7 reference observations
before they are declared useable, and this will take 14 seconds, based on a 1/2 Hz differential correction
rate. The reference model must be healthy before solutions are logged to the low latency logs, so there is
a delay in the use of real time carrier positioning to the user once the link has been re-established. The
RTK logs (RTCA/B, RTKA/B AND BSLA/B) use matched observations only (no extrapolated observations),
and these will be available after three reference observations are received, but will have about 1.5 seconds
latency associated with them.
Figure E-8 RT-20 Re-initialization Process
REFERENCE
REMOTE
RTCM59 messages
required following
RESETRT20
1
2
3
4
5
6
7
Models Generate
Reference Start generating
Doppler
reference phase Ready
models and
RTKA/B logs
RTKA/B
and
PRTKA/B
logs
The RTK system is based on a time-matched double difference observation filter. This means that observations at
the remote site have to be buffered while the reference station observation is encoded, transmitted, and decoded.
Only two seconds of remote observations are saved, so the reference station observation transmission process has
to take less than 2 seconds if any time matches are to be made. In addition, only remote observations on even
second boundaries are retained, so reference station observations must also be sent on even seconds if time matches
are to be made.
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F
Standards and References
F
STANDARDS AND REFERENCES
F
STANDARDS AND REFERENCES
RTCM STANDARDS REFERENCE
For detailed specifications of RTCM, refer to RTCM SC104 Version 2.1 of "RTCM Recommended Standards For
Differential NAVSTAR GPS Service", January 3, 1994
Radio Technical Commission for Maritime Services
655 15th Street NW, Suite 300
Washington, D.C. 20005 U.S.A.
Telephone: 202-639-4006
Fax: 202-347-8540
Website: http://www.navcen.uscg.mil/dgps/dgeninfo/RTCM104.txt
RTCA STANDARDS REFERENCE
For copies of the Minimum Aviation System Performance Standards DGNSS Instrument Approach System:
Special Category-I (SCAT-I), contact:
RTCA, Incorporated
1140 Connecticut Avenue N.W., Suite 1020
Washington, D.C. 20036-4001 U.S.A.
Telephone: 202-833-9339
Fax: 202-833-9434
Website: http://www.rtca.org
GPS SPS SIGNAL SPECIFICATION REFERENCE
For copies of the Interface Control Document (ICD)-GPS-200, contact:
ARINC Research Corporation
2551 Riva Road
Annapolis, MD 21401-7465
Telephone: 410-266-4000
Fax: 410-266-4049
Website: http://www.arinc.com
NMEA REFERENCE
National Marine Electronics Association, NMEA 0183 Standard for Interfacing Marine Electronic Devices,
Version 2.00, January 1, 1992
NMEA Executive Director
P.O. Box 50040
Mobile, Alabama 36605
U.S.A.
Website: http://www4.coastalnet.com/nmea
GEODETIC SURVEY OF CANADA
Geodetic Survey of Canada
615 Boothe Street
Ottawa, Ontario
K1A 0E9
Telephone: (613) 995-4410
Fax: (613)995-3215
Website: http://www.geod.emr.ca
U.S. NATIONAL GEODETIC SURVEY
NGS Information Services
1315 East-West Highway
Station 9244
Silver Springs, MD 20910-3282
Telephone: (301)713-2692
Fax: (301)713-4172
Website: http://www.ngs.noaa.gov
NOTE: Website addresses may be subject to change however they are accurate at the time of publication.
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G
Geodetic Datums
G
GEODETIC DATUMS
G
GEODETIC DATUMS
The following tables contain the internal ellipsoid parameters and transformation parameters used in the GPSCard.
The values contained in these tables were derived from the following DMA technical reports:
1.
TR 8350.2
Department of Defence World Geodetic System 1984 and Relationships with Local
Geodetic Systems - Revised March 1, 1988.
2.
TR 8350.2B
Supplement to Department of Defence World Geodetic System 1984 Technical Report
- Part II - Parameters, Formulas, and Graphics for the Practical Application of WGS84
- December 1, 1987.
Table G-1 Reference Ellipsoid Constants
ELLIPSOID
ID CODE
AW
AM
AN
a (metres)
6377563.396
6377340.189
6378160.0
1/f
299.3249647
299.3249647
298.25
f
Airy 1830
0.00334085064038
0.00334085064038
0.00335289186924
0.00334277318217
0.00339007530409
0.00340756137870
0.00332444929666
0.00332444929666
0.00332444929666
0.00335281068118
0.00335232986926
0.00336700336700
0.00336700336700
0.00335289186924
0.00335277945417
0.00335281066475
Modified Airy
Australian National
Bessel 1841
BR
6377397.155
6378206.4
299.1528128
294.9786982
293.465
Clarke 1866
CC
Clarke 1880
CD
6378249.145
6377276.345
6377298.556
6377304.063
6378137.0
Everest (India 1830)
Everest (Brunei & E.Malaysia)
Everest (W.Malaysia & Singapore)
Geodetic Reference System 1980
Helmert 1906
EA
300.8017
300.8017
300.8017
298.257222101
298.30
EB
ED
RF
HE
6378200.0
Hough 1960
HO
IN
6378270.0
297.00
International 1924
6378388.0
297.00
South American 1969
World Geodetic System 1972
World Geodetic System 1984
SA
6378160.0
298.25
WD
WE
6378135.0
298.26
6378137.0
298.257223563
Table G-2 Transformation Parameters (Local Geodetic to WGS84)
GPSCard
Datum ID
number
NAME
DX
DY
DZ
DATUM DESCRIPTION
ELLIPSOID
1
ADIND
-162
-12
206
Adindan (Ethiopia, Mali, Senegal & Sudan)
ARC 1950 (SW & SE Africa)
ARC 1960 (Kenya, Tanzania)
Australian Geodetic Datum 1966
Australian Geodetic Datum 1984
Bukit Rimpah (Indonesia)
Camp Area Astro (Antarctica)
Chatum 1971 (New Zealand)
Carthage (Tunisia)
Clarke 1880
2
ARC50
ARC60
AGD66
AGD84
BUKIT
ASTRO
CHATM
CARTH
CAPE
-143
-160
-133
-134
-384
-104
175
-90
-8
-294
-300
148
149
-48
Clarke 1880
3
Clarke 1880
4
-48
-48
664
-129
-38
6
Australian National
Australian National
Bessel 1841
5
6
7
239
113
431
-292
-50
International 1924
International 1924
Clarke 1880
8
9
-263
-136
-377
-130
-87
10
11
12
13
14
15
16
-108
681
110
-98
-98
684
-22
CAPE (South Africa)
Clarke 1880
DJAKA
EGYPT
ED50
Djakarta (Indonesia)
Bessel 1841
-13
Old Egyptian
Helmert 1906
-121
-119
41
European 1950
International 1924
International 1924
Bessel 1841
ED79
-86
European 1979
GUNSG
GEO49
-403
84
G. Segara (Kalimantan - Indonesia)
Geodetic Datum 1949 (New Zealand)
209
International 1924
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Geodetic Datums
Table G-2 Transformation Parameters (Local Geodetic to WGS84)
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
GRB36
GUAM
HAWAII
KAUAI
MAUI
375
-100
89
-111
-248
-279
-290
-290
-284
-222
46
431
259
-183
-172
-190
-181
114
-86
-189
-201
257
611
5
Great Britain 1936 (Ordinance Survey)
Guam 1963 (Guam Island)
Hawaiian Hawaii (Old)
Airy 1830
Clarke 1866
International 1924
International 1924
International 1924
International 1924
International 1924
International 1924
International 1924
International 1924
Everest (EA)
45
Hawaiian Kauai (Old)
65
Hawaiian Maui (Old)
OAHU
HERAT
HJORS
HONGK
HUTZU
INDIA
56
Hawaiian Oahu (Old)
-333
-73
-156
-634
289
506
-11
-97
-90
-133
-133
31
Herat North (Afghanistan)
Hjorsey 1955 (Iceland)
Hong Kong 1963
-271
-549
734
-122
851
787
40
Hu-Tzu-Shan (Taiwan)
Indian (India, Nepal, Bangladesh)
Ireland 1965
IRE65
Modified Airy
KERTA
KANDA
LIBER
LUZON
MINDA
MERCH
Kertau 1948 (West Malaysia and Singapore)
Kandawala (Sri Lanka)
Liberia 1964
Everest (ED)
86
Everest (EA)
88
Clarke 1880
-771
-70
-51
-72
47
Luzon (Philippines excluding Mindanoa Is.)
Mindanoa Island
Clarke 1866
Clarke 1866
146
Merchich (Morocco)
Clarke 1880
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
NAHR
-231
0
-196
0
482
0
Nahrwan (Saudi Arabia)
Clarke 1880
NAD83
CANADA
ALASKA
NAD27
CARIBB
MEXICO
CAMER
MINNA
OMAN
N. American 1983 (Includes Areas 37-42)
N. American Canada 1927
GRS-80
-10
-5
158
135
160
152
130
125
-93
-1
187
172
176
178
190
194
122
224
-101
-189
9
Clarke 1866
N. American Alaska 1927
Clarke 1866
-8
N. American Conus 1927
Clarke 1866
-7
N. American Caribbean
Clarke 1866
-12
0
N. American Mexico
Clarke 1866
N. American Central America
Nigeria (Minna)
Clarke 1866
-92
-346
11
Clarke 1880
Oman
Clarke 1880
PUERTO
QORNO
ROME
72
Puerto Rica and Virgin Islands
Qornoq (South Greenland)
Clarke 1866
164
-255
-134
-288
-57
-148
-206
-155
-189
-689
-128
-632
51
138
-65
229
175
1
International 1924
International 1924
International 1924
International 1924
S. American 1969
International 1924
International 1924
International 1924
International 1924
Everest (EB)
Bessel 1841
Rome 1940 Sardinia Island
South American Chua Astro (Paraguay)
South American (Provisional 1956)
South American 1969
CHUA
-29
-376
-41
90
SAM56
SAM69
CAMPO
SACOR
YACAR
TANAN
TIMBA
TOKYO
TRIST
136
172
171
-242
691
481
438
391
52
S. American Campo Inchauspe (Argentina)
South American Corrego Alegre (Brazil)
South American Yacare (Uruguay)
Tananarive Observatory 1925 (Madagascar)
Timbalai (Brunei and East Malaysia) 1948
Tokyo (Japan, Korea and Okinawa)
Tristan Astro 1968 (Tristan du Cunha)
Viti Levu 1916 (Fiji Islands)
Wake-Eniwetok (Marshall Islands)
World Geodetic System - 72
World Geodetic System - 84
Zanderidj (Surinam)
-6
37
-91
-46
664
-609
-36
-39
4.5
0
International 1924
Clarke 1880
VITI
WAK60
WGS72
WGS84
ZANDE
USER
101
0
Hough 1960
0
WGS72
0
0
WGS84
-265
0
120
0
-358
0
International 1924
User *
User Defined Datum Defaults
Notes:
*
*
*
Default user datum is WGS84.
Also see the DATUM and USERDATUM commands in Chapter 2 and Appendix C.
The GPSCard DATUM command sets the Datum value based on the name entered as listed in the "NAME" column in Table G-2 (e.g.,
NAD83).
*
These GPSCard logs report Datum used according to the "GPSCard Datum ID" column: POSA/B, PRTKA/B, RTKA/B, and MKPA/B.
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H
Some Common Unit Conversions
H
SOME COMMON UNIT CONVERSIONS
H
SOME COMMON UNIT CONVERSIONS
Section H.1 to H.4 list commonly used equivalents between the SI (Système Internationale) units of weights and
measures used in the metric system, and those used in the imperial system. A complete list of hexadecimal values
with their binary equivalents is given in Section H.5 while an example of the conversion from GPS time of week
to calendar day is shown in Section H.6.
H.1 DISTANCE
H.2 VOLUME
1 meter (m) = 100 centimeters (cm) = 1000 millimeters (mm) 1 liter (l) = 1000 cubic centimeters (cc)
1 kilometer (km) = 1000 meters (m)
1 nautical mile = 1852 meters
1 gallon (Imperial) = 4.546 liters
1 gallon (US) = 3.785 liters
1 international foot = 0.3048 meter
1 statute mile = 1609 meters
1 US survey foot = 0.3048006096 meter
H.3 TEMPERATURE
H.4 WEIGHT
degrees Celsius = (5/9) x [(degrees Fahrenheit) - 32]
degrees Fahrenheit = [(9/5) x (degrees Celsius)] + 32
1 kilogram (kg) = 1000 grams
1 pound = 0.4536 kilogram (kg)
H.5 HEXADECIMAL AND BINARY EQUIVALENTS
Hexadecimal Binary
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
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Some Common Unit Conversions
H.6 GPS TIME OF WEEK TO CALENDAR DAY (EXAMPLE)
511200 seconds
Day
511200 / 86400 seconds per day
=
5.916666667 days
Hour
.916666667 x 86400 / 3600 seconds per hour
=
22.0000 hours
0.000 minutes
0.00 seconds
Minute .000 x 3600 / 60 seconds per minute
Second .000 x 60
=
=
Day 5 (Thursday) + 22 hours, 0 minutes, 0 seconds into Friday.
H.6.1 Calendar Date to GPS Time (e.g. 11:30 hours, January 22, 1995)
Days from January 6, 1980 to January 22, 1995
=
15 years x 365 days /year
=
5475 days
Add one day for each leap year (a year which is divisible by 4 or 400 but not by 100;
every 100 years a leap year is skipped)
Days into 1997 (22nd is not finished)
4 days
21 days
Total days
5500 days
5495 days
Deduct 5 days: Jan. 1 through 5, 1980
GPS Week:
5495 x 86400 seconds per day = 474768000 seconds/ 604800 sec per week = 785
22nd day: 11.5 hrs x 3600 sec/hr 41400 seconds
Week 785, 41400 second
Seconds into week
GPS time of week:
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Information Messages
I
INFORMATION MESSAGES
I
INFORMATION MESSAGES
TYPE 1 INFORMATION MESSAGES
To date, the only Type 1 messages are the !ERRA and the !MSGA logs.
!ERRA
!ERRA
type
severity
error string opt. description
*xx [CR][LF]
Field #
Field type
Data Description
Log header
Log type, numbered 0 - 999 (see Table I-1 below)
1
2
3
4
5
6
7
!ERRA
type
severity
Only one is defined to date: severity_fatal (number = 0); causes reset
error string
opt. description
*xx
Error message (see Table I-1)
Optional description
Checksum
[CR][LF]
Sentence terminator
Example:
!ERRA,1,0,Authorization Code Invalid,*22[CR][LF]
Table I-1 Type 1 !ERRA Types
Log type
Error String
Unknown ERRA Type
0
1
Authorization Code Invalid
No Authorization Code Found
Invalid Expiry In Authorization Code
Unable To Read ESN
2
3
4
5
Reserved For Future Use
6
Card Has Stopped Unexpectedly
Reserved For Future Use
7+
!MSGA
!MSGA
type
message
opt. description
*xx
[CR][LF]
Field #
Field type
Data Description
1
2
!MSGA
type
Log header
Log type, numbered from 1000 (see Table I-2,
3
4
5
6
message
opt. description
*xx
Message (see Table I-2)
Optional description
Checksum
[CR][LF]
Sentence terminator
Example:
!MSGA,1001,Authorization Code Is Time Limited, Model 3951R Expires on
960901*6C[CR][LF]
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Information Messages
Table I-2 Type 1 !MSGA Types
Message String
Unknown MSGA Type
Log type
1000
1001
Authorization Code Is Time Limited
Reserved For Future Use
1002+
TYPE 2 INFORMATION MESSAGES
The following is a list of information messages which are generated by the Command Interpreter in response to a
user’s input. This list is not necessarily complete, but it is the most accurate one available at the time of publication.
It is intended to be a trouble-shooting tool.
Error Message
Meaning
All Ok
No errors to report.
Argument Must Be Hexadecimal (0-9,A-F) Pairs
Argument Must Be Numeric
An argument which is not hexadecimal was entered.
An argument which is not numeric was entered.
Authorization Changes Not Available On This Card
An attempt has been made to change the Authorization Code on a card which is
not an OEM card.
Authorization Code Entered Incorrectly
Authorization Code Is Invalid
The checksum is incorrect for the Authorization Code. The Authorization Code
was most likely entered incorrectly.
The existing Authorization Code is invalid. Pleasecontact NovAtelGPS customer
service for a new Authorization Code.
Can’t Change Authorization Code
Clock Model not set TM1A rejected
The existing Authorization Code cannot be changed. Please contact NovAtel
GPS customer service for assistance.
The clock model status in a $TM1A command is invalid. The $TM1A command
is rejected when the clock model has not been set.
CLOCK_ADJUST Command Not Available On This
Model
The CLOCKADJUST command is not available on this model.
Complete Almanac not received yet - try again later
The almanac cannot be saved because a complete almanac has not yet been
received. A SAVEALMA command should be performed at a later time when a
complete almanac has been received.
Data Too Large To Save To NVM
The configuration data being saved is too large.
Differential Corrections Not Available On This Model This model does not have the ability to send or receive differential corrections.
EXTERNALCLOCKCommand Not Available On This The EXTERNALCLOCK command is not available on this model.
Model
FREQUENCY_OUT Command Not Available On
This Model
The FREQUENCY_OUT command is not available on this model.
FROM port name too LONG
Invalid $ALMA CheckSum
Invalid $DCSA CheckSum
Invalid $DEBUG Options
Invalid $IONA CheckSum
Invalid $PXYA CheckSum
Invalid $REPA CheckSum
Invalid $RTCA CheckSum/CRC
Invalid $RTCM CheckSum
Invalid $TM1A CheckSum
Invalid $UTCA CheckSum
Invalid $VXYA CheckSum
Invalid ADJUSTCLOCK Option
Invalid Baudrate
The FROM port name in a SETNAV command is too long.
The checksum of a $ALMA command is invalid.
The checksum of a $DCSA command is invalid.
An invalid option was entered in the $DEBUG command.
The checksum of a $IONA command is invalid.
The checksum of a $PXYA command is invalid.
The checksum of a $REPA command is invalid.
The CRC of a $RTCA command is invalid.
The checksum of a $RTCA command is invalid.
The checksum of a $TM1A command is invalid.
The checksum of a $UTCA command is invalid.
The checksum of a $VXYA command is invalid.
An invalid CLOCKADJUST switch has been entered.
The bit rate in a COMn command is invalid.
Invalid Carrier Smoothing Constant
The carrier smoothing constant of the CSMOOTH command is invalid.
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Information Messages
Invalid Channel Number
Invalid Coarse Modulus Field
Invalid Command CRC
Invalid Command Name
Invalid Command Option
Invalid Coordinates
An invalid channel number has been entered in a command such as ASSIGN.
The coarsemod argument of the FREQUENCY_OUT command is invalid.
The received command has an invalid checksum.
An invalid command name has been received.
One or more arguments of a command are invalid.
Invalid coordinates received in a command such as $PVCA, $PXYA, etc.
The data type in an ACCEPT command is invalid.
Invalid Datatype
Invalid Datum Offset
The datum offset in a USERDATUM command is invalid.
An option in a DATUM command is invalid.
Invalid DATUM Option
Invalid Datum Rotation
Invalid Degree Field
The datum rotation angle in a USERDATUM command is invalid.
An invalid degree field has been entered in a command such as FIX POSITION
or SETNAV.
Invalid DGPS time-out value
Invalid Doppler
An invalid timeout value was entered in the DGPSTIMEOUT command.
An invalid Doppler has been entered in an ASSIGN command.
An invalid Doppler window has been entered in an ASSIGN command.
An invalid option was entered in the COMn_DTR command.
The active option in the COMn_ DTR command is invalid.
The lead time option in the COMn_ DTR command is invalid.
The tail time option in the COMn_ DTR command is invalid.
The option in a DYNAMICS command is invalid.
Invalid Doppler Window
Invalid DTR choice
Invalid DTR Toggle Option
Invalid DTR Toggle Setup Time (0-1000)
Invalid DTR Toggle Terminate Time (0-1000)
Invalid DYNAMICS Option
Invalid Echo Option
The echo option in a COMn command is invalid.
Invalid Elevation Cutoff Angle
Invalid ERRMSG Flag
The elevation cutoff angle in an ECUTOFF command is invalid.
The option (on/off) specified in a MESSAGE command is invalid.
The port specified in a MESSAGE command is invalid.
Invalid ERRMSG Port
Invalid EXTERNALCLOCK Option
Invalid EXTERNALCLOCK USER Argument(s)
Invalid Fine Modulus Field
Invalid FIX Option
An invalid external clock was entered in the EXTERNALCLOCK command.
An invalid argument was entered in the EXTERNALCLOCK command.
The finemod argument of the FREQUENCY_OUT command is invalid.
An option other than height, position or velocity was specified in a FIX command.
The flattening in a USERDATUM command is invalid.
Invalid Flattening
Invalid Handshake Option
Invalid HEALTH Override
The handshake option in a COMn command is invalid.
An invalid health has been entered in a SETHEALTH or FIX command.
The height in a FIX HEIGHT command is invalid.
Invalid Height
Invalid Logger Datatype
An invalid log has been specified in a LOG/UNLOG command.
An invalid offset has been specified in a LOG command.
An invalid period has been specified in a LOG command.
An invalid port number has been specified in a LOG/UNLOG command.
An invalid trigger has been specified in a LOG command.
The magnetic variation in a MAGVAR command is invalid.
The number of arguments in a $ALMA command is invalid.
The number of arguments in a $DCSA command is invalid.
The number of arguments in a $IONA command is invalid.
The number of arguments in a $PXYA command is invalid.
The number of arguments in a $REPA command is invalid.
The number of arguments in a $TM1A command is invalid.
The number of arguments in a $UTCA command is invalid.
The number of arguments in a $VXYA command is invalid.
A command has been received which has an invalid number of arguments.
The number of data bits in a COMn command is invalid.
The number of stop bits in a COMn command is invalid.
Invalid Logger Offset
Invalid Logger Period
Invalid Logger Port Option
Invalid Logger Trigger
Invalid Magnetic Variation
Invalid Number of $ALMA Arguments
Invalid Number of $DCSA Arguments
Invalid Number of $IONA Arguments
Invalid Number of $PXYA Arguments
Invalid Number of $REPA Arguments
Invalid Number of $TM1A Arguments
Invalid Number of $UTCA Arguments
Invalid Number of $VXYA Arguments
Invalid Number of Arguments
Invalid Number of Databits
Invalid Number of StopBits
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Information Messages
Invalid Parity Option
The parity in a COMn command is invalid.
The port in a SEND command is invalid.
Invalid Port
Invalid Port number
The port number in an ACCEPT command is invalid.
Invalid PPS Modulus Field
Invalid RINEX Option
The ppsmod argument of the FREQUENCY_OUT command is invalid.
An option of a RINEX command is invalid.
Invalid RTCA option
An invalid RTCA rule has been entered.
Invalid RTCA station Name (\XXXX\)
Invalid RTCM Bit Rule
The RTCA station name in a FIX POSITION message is invalid.
An invalid RTCM rule has been entered.
Invalid RTCM station Name (0..1023)
Invalid RTCM16T string length - maximum 90
Invalid RTS choice
The RTCM station name in a FIX POSITION message is invalid.
The RTCM16T string exceeds 90 characters.
An invalid option was entered in the COMn_RTS command.
The active option in the COMn_RTS command is invalid.
The lead time option in the COMn_RTS command is invalid.
The tail time option in the COMn_RTS command is invalid.
Invalid RTS Toggle Option
Invalid RTS Toggle Setup Time (0-1000)
Invalid RTS Toggle Terminate Time (0-1000)
Invalid Satellite Number
An invalid satellite number has been entered in an ASSIGN, SETHEALTH,
LOCKOUT or UNLOCKOUT command.
Invalid Scaling
The scale value in a USERDATUM command is invalid.
The time in a $TM1A command is invalid.
Invalid Seconds Into Week in TM1A
Invalid SemiMajor Axis
The semi-major axis in a USERDATUM command is invalid.
A standard deviation in a POSSE command is invalid.
The symbol period is invalid for an ASSIGN on a pseudolite channel.
The averaging time in a POSAVE command is invalid.
Invalid Standard Deviation Limit (0.1-100 m)
Invalid Symbol Period 1,2,4,5,10,20
Invalid Time Limit (0.1-100 hours)
Invalid Token
This error should never occur. If it does, please contact NovAtel GPS customer
service.
Invalid Track Offset
Invalid Velocity
The track offset in the SETNAV command is invalid.
An invalid velocity has been received, either in a FIX VELOCITY command, or in
a command such as $PVCA, $PVCB.
Invalid Week Number in TM1A
MET Command Not Available On This Model
Model Invalid
The week in a $TM1A command is invalid.
The MET command is not available on this model.
The Authorization Code has an invalid Model. Please contact NovAtel GPS
customer service for assistance.
NVM Error - Unable To Save
RINEX string too LONG
The SAVE operation did not complete successfully.
Indicates that the entered RINEX command is too long.
RT20 Logs Not Available On This Model
This model does not have the ability to send or receive RT20 differential
corrections.
RTCM9 Logs Not Available On This Model
SAVE Command Not Available On This Model
Save Complete
This model does not have the ability to send or receive RTCM9 logs.
A SAVE operation was attempted which is not available on this model.
The SAVE operation completed successfully.
SETCLOCK disabled TM1A rejected
The $TM1A command is rejected because the user has not enabled clock
synchronization using the SETCLOCK command.
Standard Deviation not allowed with small time limits In a POSAVE command, a standard deviation cannot be entered with a small
time. Enter a larger averaging time if standard deviations are desired.
TO Portname too LONG
The TO port name in a SETNAV command is too long.
User Defined DATUM Not Set
Thiserrorshouldnotoccur. Bydefault theuser definedDATUM issettoWGS84.
If you get this error message, please contact NovAtel GPS customer service.
Valid Option but Missing Process
This message indicates an error in the software. A command option is valid but
software cannot process it
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Listing Of Tables
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LISTING OF TABLES
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LISTING OF TABLES
This section is provided for ease of reference. The tables reproduced are as follows:
1-1
1-2
2-1
GPSCard Pseudorange Differential Initialization Summary
Latency - Induced Extrapolation Error
Commands Table
2-2
3-1
GPSCard Command Summary Chart
Logs Table
3-2
GPSCard Log Summary
4-1
Positioning Modes
C-1
C-2
C-3
D-1
D-2
D-3
D-4
D-5
D-6
D-7
D-8
D-9
D-10
D-11
D-12
E-1
E-2
E-3
E-4
E-5
Antenna LNA Power Configuration
Default Values of Process Noise Elements
VARF Range
GPSCard Solution Status
Position Type
RTK Status For Position Type 3 (RT-20)
RTK Status For Position Type 4 (RT-2)
Receiver Self-Test Status Codes
Range Record Formats (RGED only)
Channel Tracking Status
Ambiguity Types
Searcher Status
RTK Status
GPSCard Range Reject Codes
GPSCard Velocity Status
Comparison of RT-2 and RT-20
RTK Messages Vs. Accuracy
RT-2 Performance - Static Mode
RT-2 Performance - Kinematic Mode
RT-20 Performance
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Listing Of Tables
Table 1-1 GPSCard Pseudorange Differential Initialization Summary
Reference Station Remote Station
Required:
Required:
FIX POSITION lat lon hgt id (health)
ACCEPT port DATATYPE
LOG port DATATYPE ontime 5
Recommended Options:
Recommended Options:
LOG DATATYPES (binary):
ACCEPT DATATYPES (binary):
RTCMB
RTCAB
RTCM
RTCA
RTCM
RTCA
LOG DATATYPES (acii):
ACCEPT COMMANDS (ascii):
RTCMA
RTCAA
RTCMA
RTCAA
Related Commands/Logs:
Related Commands/Logs:
RTCMRULE
RTCMRULE
DATUM
POSA/B
VLHA/B
CDSA/B
GPGGA
DATUM
Example 1:
Example 1:
fix position 51.3455323 -114.2895345 1201.123 555 0
log com 1 RTCM ontime 2
accept com2 rtcm
log com1 posa ontime 1
Example 2:
Example 2:
fix position 51.3455323 -114.2895345 1201.123 555 0
log com2 rtcaa ontime 2
accept com2 commands
log com1 posa ontime 0.2
log com1 vlha ontime 0.2
Note: Italicized entries indicate user definable.
Table 1-2 Latency-Induced Extrapolation Error
Time since last reference station observation
Typical extrapolation error (CEP)
0-2 seconds
2-7 seconds
7-30 seconds
1 cm/sec
2 cm/sec
5 cm/sec
Table 2-1 Commands By Function Table
COMMUNICATIONS, CONTROL AND STATUS
Commands
Descriptions
Power to the low-noise amplifier of an active antenna
COMn port configuration control
DTR handshaking control
ANTENNAPOWER
COMn
COMn_DTR
COMn_RTS
RTS handshaking control
1
Differential Protocol Control
DIFF_PROTOCOL
FREQUENCY_OUT
LOG
Variable frequency output (programmable)
Logging control
MESSAGES
RINEX
Disable error reporting from command interpreter
Configure the user defined fields in the file header
Sets up RTCM bit rule
RTCMRULE
RTCM16T
SEND
Enters an ASCII message
Sends ASCII message to COM port
Sends non-printable characters
SENDHEX
Add an offset to the L1 pseudorange to compensate for
signal delays
1
SETL1OFFSET
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Listing Of Tables
1
Intended for advanced users of GPS onl
GENERAL RECEIVER CONTROL AND STATUS
Commands Descriptions
$ALMA
Download almanac data file
CRESET
Reset receiver to factory default
Set correlator tracking bandwidth
On-line command help
DYNAMICS
HELP
RESET
Performs a hardware reset (OEM only)
Saves the latest almanac in NVM
Saves current configuration (OEM only)
Injects receiver time of 1PPS
SAVEALMA
SAVECONFIG
$TM1A
VERSION
Software/hardware information
POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL
Commands Descriptions
1
Sets amount of carrier smoothing
CSMOOTH
DATUM
Choose a DATUM name type
ECUTOFF
FIX HEIGHT
FIX POSITION
FRESET
Satellite elevation cut-off for solutions
Constrains to fixed height (2D mode)
Constrains to fixed lat, lon, height
Clears all data which is stored in NVM
Download ionospheric correction data
$IONA
What ionospheric correction to use (MiLLennium with the
WAAS option)
IONOMODEL
LOCKOUT
Deweights a satellite in solutions
1
Position, velocity and acceleration in ECEF coordinates
$PVAA
RTKMODE
Setup the RTK mode
UNDULATION
USERDATUM
WAASCORRECTION
Ellipsoid-geoid separation
User-customized datum
Controls handling of WAAS corrections.
1
Intended for advanced users of GPS only.
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Listing Of Tables
SATELLITE TRACKING AND CHANNEL CONTROL
Commands Descriptions
$ALMA
ASSIGN
CONFIG
Download almanac data file
Satellite channel assignment
Switches the channel configuration of the GPSCard
Sets correlator tracking bandwidth
Aids high velocity reacquisition
Reset PRN health
DYNAMICS
FIX VELOCITY
RESETHEALTH
SETHEALTH
Overrides broadcast satellite health
WAYPOINT NAVIGATION
Commands
Descriptions
Magnetic variation correction
Waypoint input
MAGVAR
SETNAV
DIFFERENTIAL REFERENCE STATION
Commands
Descriptions
DGPSTIMEOUT
FIX POSITION
LOG
Sets ephemeris delay
Constrain to fixed (reference)
Selects required differential-output log
Implements position averaging for reference station
Selects RTCM bit rule
POSAVE
RTCMRULE
SETDGPSID
Set reference station ID
DIFFERENTIAL REMOTE STATION
Commands
Descriptions
Accepts RTCM1, RTCA or RTCAB differential inputs
Input almanac data
ACCEPT
$ALMA
DGPSTIMEOUT
RESET
Set maximum age of differential data accepted
Performs a hardware reset
$RTCA
RTCA differential correction input (ASCII)
RTCM differential correction input (ASCII)
Selects RTCM bit rule
$RTCM
RTCMRULE
SETDGPSID
Select differential reference station ID to receive
CLOCK INFORMATION, STATUS, AND TIME
Commands
Descriptions
Enable clock modelling & 1PPS adjust
Differential protocol control
CLOCKADJUST
1
DIFF_PROTOCOL
EXTERNALCLOCK
Sets default parameters of an optional external oscillator
EXTERNALCLOCK FREQUENCY Sets clock rate
1
Enable or disable time synchronization
Download UTC data
SETTIMESYNC
$UTCA
1
Intended for advanced users of GPS only
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Listing Of Tables
Table 2-2 GPSCard Command Summary
Description
Command
Syntax
$ALMA
Injects almanac
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
accept port,option
$IONA
Injects ionospheric refraction corrections
Injects latest computed position, velocity and acceleration
Injects raw GPS ephemeris data
Injects RTCA format DGPS corrections in ASCII (Type 1)
Injects RTCM format differential corrections in ASCII (Type 1)
Injects receiver time of 1 PPS
$PVAA
$REPA
$RTCA
$RTCM
$TM1A
$UTCA
Injects UTC information
ACCEPT
Port input control (set command interpreter)
Power to the low-noise amplifier of an active antenna
Assign a prn to a channel #
ANTENNAPOWER
ASSIGN
antennapower flag
assign channel,prn,doppler, search window
unassign channel
UNASSIGN
UNASSIGNALL
CLOCKADJUST
COMn
Un-assign a channel
Un-assign all channels
unassignall
Disable clock steering mechanism
Initialize Serial Port (1 or 2)
clockadjust switch
comn bps,parity,databits,stopbits, handshake,echo
comn_dtr control,active,lead,tail
comn_rts control,active,lead,tail
config cfgtype
COMn_DTR
COMn_RTS
CONFIG
Programmable DTR lead/tail time
Programmable RTS lead/tail time
Switches the channel configuration of the GPSCard
Configuration reset to factory default
Sets carrier smoothing
CRESET
creset
CSMOOTH
DATUM
csmooth value
Choose a DATUM name type
datum option
USERDATUM
User defined DATUM
userdatum semi-major,flattening,dx,dy,dz, rx,ry,rz,
scale
DGPSTIMEOUT
Sets maximum age of differential data to be accepted and ephemeris dgpstimeout value value
delay
DIFF_PROTOCOL
Differential correction message encoding and decoding for
implementation in the GPS card firmware
diff_protocol type key
or diff_protocol disable
or diff_protocol
DYNAMICS
Set receiver dynamics
dynamics option [user_dynamics]
ecutoff angle
ECUTOFF
Set elevation cutoff angle
EXTERNALCLOCK
Sets default parameters of an optional external oscillator
Sets clock rate
externalclock option
EXTERNALCLOCK
FREQUENCY
external frequency clock rate
FIX HEIGHT
Sets height for 2D navigation
fix height height [auto]
FIX POSITION
FIX VELOCITY
Set antenna coordinates for reference station
fix position lat,lon,height [station id] [health]
Accepts INS xyz (ECEF) input to aid in high velocity reacquisition of fix velocity vx,vy,vz
SVs
UNFIX
Remove all receiver FIX constraints
Variable frequency output (programmable)
Clears all data which is stored in non-volatile memory
On-line command help
unfix
FREQUENCY_OUT
FRESET
frequency_out n,k
freset
HELP or ?
LOCKOUT
UNLOCKOUT
UNLOCKOUTALL
LOG
help option or
lockout prn
unlockout prn
unlockoutall
? option
Lock out satellite
Restore satellite
Restore all satellites
Choose data logging type
log [port],datatype,[trigger],[period],[offset],{hold}
unlog [port],data type
unlogall [port]
UNLOG
Disable a data log
UNLOGALL
MAGVAR
MESSAGES
POSAVE
Disable all data logs
Set magnetic variation correction
Disable error reporting from command interpreter
Implements position averaging for reference station
Performs a hardware reset (OEM only)
Configure the user defined fields in the file headers
magvar value
messages port,option
posave maxtime, maxhorstd, maxverstd
reset
RESET
RINEX
rinex cfgtype
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Listing Of Tables
RTCM16T
Enter an ASCII text message to be sent out in the RTCM data stream rtcm16t ascii message
RTCMRULE
RTKMODE
Set variations of the RTCM bit rule
Set up the RTK mode
rtcmrule rule
rrtkmode argument, data range
savealma option
SAVEALMA
SAVECONFIG
SEND
Save the latest almanac in non-volatile memory
Save current configuration in non-volatile memory (OEM only)
Send an ASCII message to any of the communications ports
Sends non-printable characters in hexadecimal pairs
Enter in a reference station ID
saveconfig
send port ascii-message
sendhex port data
setdgpsid option
sethealth prn,health
resethealth prn
SENDHEX
SETDGPSID
SETHEALTH
RESETHEALTH
RESETHEALTHALL
SETL1OFFSET
SETNAV
Override PRN health
Reset PRN health
Reset all PRN health
resethealthall
Add an offset to the L1 pseudorange to compensate for signal delays setL1offset distance
Set a destination waypoint
setnav from lat,from lon,to lat, to lon,track offset, from
port,to port
SETTIMESYNC
UNDULATION
VERSION
Enable or disable time synchronization
Choose undulation
settimesync flag
undulation separation
version
Current software and hardware information
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Table 3-1 Logs By Function Table
COMMUNICATIONS, CONTROL AND STATUS
Descriptions
Logs
CDSA/B
COM port communications status
Log data from COM1
COM1A/B
COM2A/B
COMnA/B
RCSA/B
Log data from COM2
Pass-through data logs
Receiver self-test status
RTCM16T
RTCM16
NovAtel ASCII format special message
RTCM format special message
GENERAL RECEIVER CONTROL AND STATUS
Descriptions
Logs
PVAA/B
RCCA
Receiver’s latest computed position, velocity and acceleration in ECEF coordinates
Receiver configuration status
RCSA/B
RVSA/B
VERA/B
Version and self-test status
Receiver status
Receiver hardware and software version numbers
POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL
Logs Descriptions
DOPA/B
GGAB
DOP of SVs currently tracking
GPS fix data
GPGGA
GPGLL
GPGRS
GPGSA
GPGST
NMEA, position data
NMEA, position data
NMEA, range residuals
NMEA, DOP information
NMEA, measurement noise statistics
Position at time of mark
MKPA/B
POSA/B
PRTKA/B
PVAA/B
PXYA/B
RTKA/B
SPHA/B
Position data
Computed position
Computed position, velocity and acceleration in ECEF coordinates
Position (Cartesian x,y,z coordinates)
Computed position
Speed and direction over ground
SATELLITE TRACKING AND CHANNEL CONTROL
Descriptions
Logs
ALMA/B
DOPA/B
ETSA/B
GPALM
GPGSA
Current decoded almanac data
DOP of SVs currently tracking
Provides channel tracking status information for each of the GPSCard parallel channels
NMEA, almanac data
NMEA, SV DOP information
GPGSV
NMEA, satellite-in-view information
Raw almanac
RALA/B
RASA/B
RGEA/B/D
SATA/B
SBTA/B
SVDA/B
WRCA/B
Raw GPS almanac set
Satellite range measurements
Satellite specific information
Satellite broadcast data (raw symbols)
SV position (ECEF xyz)
Wide band range correction data (grouped format)
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WAYPOINT NAVIGATION
Descriptions
Logs
GPRMB
GPRMC
GPVTG
GPZTG
NMEA, waypoint status
NMEA, navigation information
NMEA, track made good and speed
NMEA, time to destination
Position at time of mark input
Navigation waypoint status
Position data
MKPA/B
NAVA/B
POSA/B
SPHA/B
VLHA/B
Speed and course over ground
Velocity, latency & direction over ground
DIFFERENTIAL REFERENCE STATION
Descriptions
Logs
ALMA/B
CDSA/B
CMR
Current almanac information
COM port data transmission status
Pseudorange and carrier phase data
PAVA/B
RGEA/B/D
RPSA/B
RTCAA/B
RTCM1
Parameters being used in the position averaging process
Channel range measurements
Reference station position and health
Transmits RTCA differential corrections in NovAtel ASCII or Binary
Transmits RTCM SC104 standard corrections
Reference position
RTCM3
RTCM1819
RTCM22
RTCM59
RTCMA/B
SATA/B
Uncorrected carrier phase and pseudorange measurements
Extended reference station parameters
NovAtel format RT-20 observation data
Transmits RTCM information in NovAtel ASCII/binary
Satellite specific information
DIFFERENTIAL REMOTE STATION
Descriptions
Logs
CDSA/B
GPGGA
GGAB
Communication and differential decode status
NMEA, position fix data
NovAtel binary version of GPGGA
Position information
POSA/B
PRTKA/B
RTKA/B
RTKOA/B
SATA/B
SVDA/B
VLHA/B
Computed Position – best available
Computed Position – Time Matched
RTK Output
Satellite specific information
SV position in ECEF XYZ with corrections
Velocity, latency & direction over ground
POST PROCESSING DATA
Descriptions
Logs
BSLA/B
CLKA/B
REPA/B
RGEA/B/D
SATA/B
SVDA/B
Most recent matched baseline expressed in ECEF coords.
Receiver clock offset information
Raw ephemeris information
Satellite and ranging information
Satellite specific information
SV position in ECEF XYZ with corrections
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CLOCK INFORMATION, STATUS, AND TIME
Descriptions
Logs
CLKA/B
Receiver clock offset information
1
Current clock-model matrices of the GPSCard
NMEA, UTC time and date
NMEA, UTC and time to waypoint
Time of mark input
CLMA/B
GPZDA
GPZTG
MKTA/B
TM1A/B
Time of 1PPS
1
Intended for advanced users of GPS only.
NAVIGATION DATA
Descriptions
Logs
FRMA/B
RALA/B
RASA/B
RBTA/B
REPA/B
Framed raw navigation data
Raw almanac and health data
Raw almanac set
Satellite broadcast data in raw bits
Raw ephemeris data
Table 3-2 GPSCard Log Summary
Syntax: log port,datatype,[trigger],[period],[offset],{hold}
NovAtel Format Logs
Datatype
Description
Datatype
RASA/B
RCCA
Description
Raw GPS Almanac Set
Receiver Configuration
Raw Ephemeris
Channel Range Measurements
Reference Station Position and Health
RTCA format Differential Corrections with NovAtel headers
Computed Position - Time Matched
RTK Solution Parameters
RTCM Type 1 Differential Corrections with NovAtel headers
Special Message
ALMA/B
BSLA/B
CDSA/B
CLKA/B
CLMA/B
COM1A/B
COM2A/B
DOPA/B
ETSA/B
GGAB
MKPA/B
MKTA/B
NAVA/B
PAVA/B
POSA/B
PRTKA/B
PVAA/B
PXYA/B
RALA/B
Decoded Almanac
Baseline Measurement
Communication and Differential Decode Status
Receiver Clock Offset Data
Receiver Clock Model
Log data from COM1
Log data from COM2
REPA/B
RGEA/B/D
RPSA/B
RTCAA/B
RTKA/B
RTKOA/B
RTCMA/B
RTCM16T
RVSA/B
SATA/B
SBTA/B
SPHA/B
SVDA/B
TM1A/B
VERA/B
VLHA/B
WRCA/B
Dilution of Precision
Extended Tracking Status
Global Position System Fix Data - Binary Format
Mark Position
Receiver Status
Satellite Specific Data
Time of Mark Input
Navigation Data
Satellite Broadcast Data (Raw Symbols)
Speed and Direction Over Ground
SV Position in ECEF XYZ Coordinates with Corrections
Time of 1PPS
Receiver Hardware and Software Version Numbers
Velocity, Latency, and Direction over Ground
Wide Band Range Correcion (Grouped)
Positioning Averaging Status
Computed Position
Computed Position
XYZ Position, Velocity and Acceleration
Computed Cartesian Coordinate Position
Raw Almanac
NMEA Format Logs
GPALM
GPGGA
GPGLL
GPGRS
GPGSA
GPGST
Almanac Data
Global Position System Fix Data
Geographic Position - lat/lon
GPS Range Residuals for Each Satellite
GPS DOP and Active Satellites
Pseudorange Measurement Noise Statistics
GPGSV
GPRMB
GPRMC
GPVTG
GPZDA
GPS Satellites in View
Generic Navigation Information
GPS Specific Information
Track Made Good and Ground Speed
UTC Time and Date
GPZTG
UTC & Time to Destination Waypoint
RTCA Format
RTCA
RTCA Differential Corrections: Type 1 and Type 7
RTCM Format
RTCM1
RTCM3
Type 1 Differential GPS Corrections
Type 3 Reference Station Parameters
RTCM9
Type 9 Partial Satellite Set Differential Corrections
Type 16 Special Message
Type 18 and Type 19 Uncorrected Carrier Phase and Pseudorange Corrections
Type 22 Extended Reference Station Parameters
RTCM16
RTCM1819
RTCM22
RTCM59
Type 59N-0 NovAtel Proprietary Message: RT20 Differential Observations
Note A/B/D:
A
B
D
refers to GPSCard output logs in ASCII format.
refers to GPSCard output logs in Binary format.
refers to GPSCard output logs in compressed binary format.
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Table 4-1 Positioning Modes
Reference station: Reference station: Reference station: Reference station:
L1
L1
L1 & L2
RTCM Type 59N
L1 & L2
RTCA Type 7
RTCM Type 59N
RTCA Type 7
Remote station: L1
RT-20
RT-20
RT-20
RT-20
RT-20
RT-20
RT-20
Remote station: L1 & L2
RT-2
Table C-1 Antenna LNA Power Configuration
P301: plug connects
pins 1&2
P301: plug connects
pins 2&3
P301: no plug
internal power connected to no external effect
LNA
no external effect
no external effect
ANTENNAPOWER = ON
ANTENNAPOWER = OFF
internal power cut off from
LNA
no external effect
Table C-2 Default Values of Process Noise Elements
h
h
h
-2
Timing Standard
0
-1
VCTCXO
OCXO
1.0 e-21
2.51 e-26
1.0 e-23
2.0 e-20
1.0 e-20
2.51 e-23
1.0 e-22
7.0 e-23
2.0 e-20
2.51 e-22
1.3 e-26
4.0 e-29
rubidium
cesium
user (min / max)
1.0 e-31 ≤ h ≤ 1.0 e-18
1.0 e-31 ≤ h ≤ 1.0 e-18
1.0 e-31 ≤ h ≤ 1.0 e-18
-2
0
-1
Table C-3 VARF Range (Software Version 4.42 or higher)
p VARF (Hz)
n
k
1
1
1
0
(Minimum)
(Maximum)
1024
65 536 65 536 0.004 652 065
65 536 65 536 0.004 656 612
1
1
2
1
4000
4
5000
8
1
312 500
5 000 000
2
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Table D-1 GPSCard Solution Status
Description
Value
0
Solution computed
1
2
3
Insufficient observations
No convergence
T
Singular A PA Matrix
4
5
6
7
Covariance trace exceeds maximum (trace > 1000 m)
Test distance exceeded (maximum of 3 rejections if distance > 10 km)
Not yet converged from cold start
Height or velocity limit exceeded. (In accordance with COCOM export
licensing restrictions)
Higher numbers are reserved for future use
Table D-2 Position Type
Type
Definition
0
1
2
3
4
5
No position
Single point position
Differential pseudorange position
RT-20 position
RT-2 position
WAAS position solution
Higher numbers are reserved for future use
Table D-3 RTK Status for Position Type 3 (RT-20)
Definition
Status
0
1
2
3
4
5
6
7
8
Floating ambiguity solution (converged)
Floating ambiguity solution (not yet converged)
Modelling reference phase
Insufficient observations
Variance exceeds limit
Residuals too big
Delta position too big
Negative variance
RTK position not computed
Higher numbers are reserved for future use
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Table D-4 RTK Status for Position Type 4 (RT-2)
Definition
Status
0
Narrow lane solution
1
2
3
4
5
6
7
8
9
10
Wide lane derived solution
Floating ambiguity solution (converged)
Floating ambiguity solution (not yet converged)
Modelling reference phase
Insufficient observations
Variance exceeds limit
Residuals too big
Delta position too big
Negative variance
RTK position not computed
Higher numbers are reserved for future use
Table D-5 Receiver Self-Test Status Codes
N7
N
6
N 5
N 4
N 3
N 2
N 1
N 0
<- Nibble
<- Number
Bit Description Range Values
lsb ANTENNA
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Hex Value
00000001
1 = good, 0 = bad
=
0
1
2
3
4
5
6
7
8
9
L1 PLL
RAM
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = not set, 0 = set
1 = not set, 0 = set
00000002
00000004
00000008
00000010
00000020
00000040
00000080
00000100
00000200
ROM
DSP
L1 AGC
COM 1
COM 2
WEEK
NO
COARSETIME
10 NO FINETIME
1 = not set, 0 = set
00000400
00000800
00001000
00002000
00004000
11 L1 JAMMER
1 = present, 0 = normal
12 BUFFER COM 1 1 = overrun, 0 = normal
13 BUFFER COM 2 1 = overrun, 0 = normal
14 BUFFER
CONSOLE
1 = overrun, 0 = normal
15 CPU OVERLOAD 1 = overload, 0 = normal 00008000
16 ALMANAC
SAVED IN NVM
1 = yes, 0 = no
00010000
17 L2 AGC
1 = good, 0 = bad
1 = present, 0 = normal
1 = good, 0 = bad
1 = good, 0 = bad
1 = yes, 0 = no
00020000
00040000
00080000
00100000
00200000
18 L2 JAMMER
19 L2 PLL
20 OCXO PLL
21 SAVED ALMA.
NEEDS UPDATE
22 ALMANAC
INVALID
23 POSITION
SOLUTION
1=invalid, 0=valid
1=invalid, 0=valid
00400000
00800000
INVALID
24 POSITION FIXED 1 = yes, 0 = no
01000000
02000000
25 CLOCK MODEL 1=invalid, 0=valid
INVALID
26 CLOCK
STEERING
1 = disabled, 0 = enabled 04000000
DISABLED
27 RESERVED
28- RESERVED
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Notes on Table D-5:
1. Bit 3: On OEM GPSCards, “ROM” includes all forms of non-volatile memory.
2. Bits 12-15: Flag is reset to 0 five minutes after the last overrun/overload condition has occurred.
Table D-6 Range Record Format (RGED only)
Data
Bit(s) from first to last
Length (bits)
Format
integer
Scale Factor
1A, 1B
0..5
6
1
PRN
2
3
4
6..10
11.31
32..63
5
integer
(20+n) dB-Hz
1/32 s
C/No
21
32
integer
Lock time
ADR
integer 2’s comp.
1/256 cycles
Doppler frequency
Pseudorange
68..95
28
36
4
integer 2’s comp.
integer 2’s comp.
integer
1/256 Hz
64..67 msn; 96..127 lsw
128..131
1/128 m
StdDev - ADR
(n+1) / 512 cyc
5
StdDev - pseudorange
Channel Tracking status
Notes on Table D-6:
132..135
4
see
6
136..159
24
integer
1A
Only PRNs 1 - 63 are reported correctly (Note: while there are only 32 PRNs in the basic GPS scheme,
situations exist which require the use of additional PRNs)
1B
The prn offsets for WAAS have been mapped to the same range as GPS, ie. 1 - 19, while the prn offsets
for GLONASS are 1 - 29.
2
C/No is constrained to a value between 20 - 51 dB-Hz. Thus, if it is reported that C/No = 20 dB-Hz, the
actual value could be less. Likewise, if it is reported that C/No = 51 dB-Hz, the true value could be greater.
3
4
Lock time rolls over after 2,097,151 seconds.
ADR (Accumulated Doppler Range) is calculated as follows:
ADR_ROLLS = ( -RGED_PSR / WAVELENGTH - RGED_ADR) / MAX_VALUE
Round to the closest integer
IF (ADR_ROLLS ≤ -0.5)
ADR_ROLLS = ADR_ROLLS - 0.5
ELSE
ADR_ROLLS = ADR_ROLLS + 0.5
At this point integerise ADR_ROLLS
CORRECTED_ADR = RGED_ADR + (MAX_VALUE * ADR_ROLLS)
where:
ADR has units of cycles
WAVELENGTH = 0.1902936727984 for L1
WAVELENGTH = 0.2442102134246 for L2
MAX_VALUE = 8388608
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5
Code
RGED
0
0.000 to 0.050
0.051 to 0.075
0.076 to 0.113
0.114 to 0.169
0.170 to 0.253
0.254 to 0.380
0.381 to 0.570
0.571 to 0.854
0.855 to 1.281
1.282 to 2.375
2.376 to 4.750
4.751 to 9.500
9.501 to 19.000
19.001 to 38.000
38.001 to 76.000
76.001 to 152.000
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
6
Only bits 0 - 23 are represented in the RGED log
Table D-7 Channel Tracking Status
N 7
N 6
N 5
N 4
N 3
N 2
N 1
N 0
<- <- Nibble Number
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Bit
lsb=0
Description
Range Values
Hex.
1
1
2
3
4
5
Tracking state
0 - 11 See below
2
4
8
10
20
0 - n (0=first, n=
last)
6
7
8
9
Channel number
Phase lock flag
(n depends on GPSCard) 40
80
100
1 = Lock, 0 = Not locked 200
10 Parity known flag
1 = Known, 0 = Not
known
400
11 Code lockedflag
1 = Lock, 0 = Not locked 800
12
1000
13 Correlator spacing
0 - 7 See below
2000
4000
14
15
0=GPS 3= Pseudolite 8000
GPS
16 Satellitesystem
1=GLONASS 4-7
Reserved
10000
17
2=WAAS
20000
40000
80000
18 Reserved
19 Grouping
1 = Grouped, 0 = Not
grouped
20 Frequency
21 Code type
1 = L2, 0 = L1
100000
200000
0 = C/A 2 = P-
codeless
22
1 =P
3= Reserved 400000
23 Forward error correction
1 = FEC enabled, 0 = no 800000
FEC
24
:
Reserved
29
30 External range
1 = Ext. range, 0 = Int.
range
31 Channel assignment
1 = Forced, 0 =
Automatic
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Table D-7 is referenced by the ETSA/B, and RGEA/B/D logs.
Table D-7, Bits 0 - 3: Channel Tracking State
State
Description
State
Description
L1 Steering
0
1
2
3
4
5
L1 Idle
6
L1 Sky search
7
L1 Frequency-lock loop
L2 Idle
L1 Wide frequency band pull-in
L1 Narrow frequency band pull-in
L1 Phase-lock loop
8
9
L2 P-code alignment
L2 Search
10
11
L1 Re-acquisition
L2 Phase-lock loop
Higher numbers are reserved for future use
Table D-7, Bits 12-14: Correlator Spacing
State
Description
0
1
2
Unknown: this only appears in versions of software previous to x.45, which didn’t use this field
Standard correlator: spacing = 1 chip
Narrow Correlator tracking technology: spacing < 1 chip
Higher numbers are reserved for future use
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Table D-8 Ambiguity Types
Definition
Ambiguity Type
0
1
L1 only floating
Wide lane fixed integer
Reserved
2
3
Narrow lane floating
Iono–free floating
Reserved
4
5
6
Narrow lane fixed integer
Iono–free fixed discrete
L1 only fixed integer
Reserved
7
8
9
10
Undefined type
Higher numbers are reserved for future use
Table D-9 Searcher Status
Definition
Searcher Status
0
1
2
3
4
No search requested
Searcher buffering measurements
Currently searching
Search decision made
Hand-off to L1 and L2 complete
Higher numbers are reserved for future use
Table D-10 RTK Status
Definition
RTK Status
1
2
Good narrowlane solution
Good widelane solution
4
Good L1/L2 converged float solution
Good L1/L2 unconverged float solution
Good L1 converged solution
Good L1 unconverged solution
Reserved for future use
Insufficient observations
Variance exceeds limit
Residuals exceed limit
Delta position too large
Negative variance
8
16
32
64
128
256
512
1024
2048
4096
8192
Undefined
RTK initialize
Higher numbers are reserved for future use
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Table D-11 GPSCard Range Reject Codes
Description
Value
0
Observations are good
1
Bad satellite health is indicated by ephemeris data
2
Old ephemeris due to data not being updated during last 3 hours
Eccentric anomaly error during computation of the satellite’s position
True anomaly error during computation of the satellite’s position
Satellite coordinate error during computation of the satellite’s position
Elevation error due to the satellite being below the cutoff angle
Misclosure too large due to excessive gap between estimated and actual positions
No differential correction is available for this particular satellite
Ephemeris data for this satellite has not yet been received
Invalid IODE due to mismatch between differential stations
Locked Out: satellite is excluded by user (LOCKOUT command)
Low Power: satellite rejected due to low signal/noise ratio
L2 measurements are not currently used in the filter
3
4
5
6
7
8
9
10
11
12
13
Higher numbers are reserved for future use
Table D-12 GPSCard Velocity Status
Description
Value
0
1
2
3
4
5
Velocity computed from differentially corrected carrier phase data
Velocity computed from differentially corrected Doppler data
Old velocity from differentially corrected phase or Doppler (higher latency)
Velocity from single point computations
Old velocity from single point computations (higher latency)
Invalid velocity
Higher numbers are reserved for future use
Table E-1 Comparison of RT-2 and RT-20
RT-2
RT-20
L1
L1 & L2
GPS Frequencies Utilized
Nominal Accuracy
Lane Searching
2 cm (CEP)
20 cm (CEP)
None
Wide lane and narrow lane
.
Table E-2 RTK Messages Vs. Accuracy
Transmitting (Reference)
Receiving (Remote)
Accuracy Expected
Standard GPSCard transmitting RTCA
MiLLennium RT-2 receiver
2 centimetre CEP
GPSCard RT-20 receiver
20 centimetre CEP
20 centimetre CEP
Standard GPSCard transmitting RTCM type 3 and 59 MiLLennium RT-2 receiver
GPSCard RT-20 receiver
20 centimetre CEP
20 centimetre CEP
20 centimetre CEP
1 metre SEP
RT-20 GPSCard transmitting RTCM type 3 and 59
MiLLennium RT-2 receiver
GPSCard RT-20 receiver
MiLLennium RT-2 receiver
RT-20 Standard GPSCard transmitting RTCM or
GPSCard RT-20 receiver
MiLLennium RT-2 receiver
1 metre SEP
Standard GPSCard transmitting RTCM type 18 and
20 centimetre CEP
RT-20 receiver
n/a
1
The RTCM1819 message can only be transmitted and received by MiLLennium GPSCards
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Table E-3 RT-2 Performance: Static Mode
Time since L2 lock-on
with at least 6 satellites
above mask angle
Runs meeting the stat-
ed accuracy at the
stated time
Baseline
length
Horizontal accuracy at
the stated time
< 10 km
< 10 km
< 15 km
< 25 km
< 35 km
< 35 km
70 seconds + 1.5 sec/km
5 minutes
2 cm + 0.5 ppm
1 cm + 1 ppm
5 cm
75.0%
75.0%
66.7%
66.7%
66.7%
66.7%
4 minutes
7 minutes
7 cm
10 minutes
35 cm
30 minutes
25 cm
Table E-4 RT-2 Performance: Kinematic Mode
Time since L2 lock-on
with at least 6 satellites
above mask angle
Runs meeting the
stated accuracy at
the stated time
Baseline
length
Horizontal accuracy at
the stated time
< 10 km
< 15 km
< 25 km
< 35 km
< 35 km
120 seconds + 1.5 sec/km
8 minutes
2 cm + 0.5 ppm
8 cm
75.0%
66.7%
66.7%
66.7%
66.7%
14 minutes
10 cm
20 minutes
40 cm
60 minutes
25 cm
Table E-5 RT-2 Degradation With Respect To Data Delay 1
Data Delay (sec)
Distance (km)
Accuracy (CEP)
+1 cm/sec
0 - 2
2 - 7
7 - 30
> 30
1
1
1
1
+2 cm/sec
+5 cm/sec
3
pseudorange or single point
Table E-6 RT-20 Performance
Data Delay (sec) Distance (km)
1
Tracking Time (sec)
Accuracy (CEP)
Mode
Static
1 - 180
0
1
1
1
100 to 25 cm
180 - 3000
> 3000
Static
Static
0
0
25 to 5 cm
2
2
5 cm or less
100 to 25 cm
25 to 5 cm
1 - 600
Kinematic
Kinematic
Kinematic
0
0
0
1
1
1
600 - 3000
> 3000
5 cm or less
+1 cm/sec
+2 cm/sec
+5 cm/sec
Either
Either
Either
Either
0 - 2
2 - 7
7 - 30
> 30
1
1
1
1
3
pseudorange or single point
1
Mode = Static or Kinematic
2 The accuracy specifications refer to the PRTKA/B logs which include about 3 cm extrapolation error. RTKA/B logs are more accurate
but have increased latency associated with them.
3
After 30 seconds reverts to pseudorange positioning (single point or differential depending on messages previously
received from the base station).
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GPS Glossary of Terms
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GPS GLOSSARY OF TERMS
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GPS Glossary of Terms
ASCII — A 7 bit wide serial code describing numbers, upper and lower case characters, special and non-printing
characters.
Address field — for sentences in the NMEA standard, the fixed length field following the beginning sentence
delimiter "$" (HEX 24). For NMEA approved sentences, composed of a two character talker
identifier and a three character sentence formatter. For proprietary sentences, composed of the
character "P" (HEX 50) followed by a three character manufacturer identification code.
Almanac — a set of orbit parameters that allows calculation of approximate GPS satellite positions and
velocities. The almanac is used by a GPS receiver to determine satellite visibility and as an aid
during acquisition of GPS satellite signals.
Almanac data — a set of data which is downloaded from each satellite over the course of 12.5 minutes. It
contains orbital parameter approximations for all satellites, GPS to universal time conversion
parameters, and single-frequency ionospheric model parameters.
Arrival alarm — an alarm signal issued by a voyage tracking unit which indicates arrival at or at a pre-
determined distance from a waypoint [see arrival circle].
Arrival circle — an artificial boundary placed around the destination waypoint of the present navigation leg,
and entering of which will signal an arrival alarm.
Arrival perpendicular — crossing of the line which is perpendicular to the course line and which passes
through the destination waypoint.
Attenuation — reduction of signal strength
Attitude — the position of an aircraft or spacecraft in relation to a given line or plane, as the horizon.
Azimuth — the horizontal direction of a celestial point from a terrestrial point, expressed as the angular
distance from 000° (reference) clockwise through 360°. The reference point is generally True North,
but may be Magnetic North, or Relative (ship's head).
Bearing — the horizontal direction of one terrestrial point from anther terrestrial point, expressed as the
angular distance from a reference direction, usually measured from 000° at the reference direction
clockwise through 360°. The reference point may be True North, Magnetic North, or Relative (ship's
head).
Carrier — the steady transmitted RF signal whose amplitude, frequency, or phase may be modulated to carry
information.
Carrier Phase Ambiguity (or sometimes ambiguity for short) — the number of integer carrier phase cycles
between the user and the satellite at the start of tracking.
Carrier phase measurements — these are “accumulated delta range” measurements. They contain the
instantaneous phase of the signal (modulo 1 cycle) plus some arbitrary number of integer cycles.
Once the receiver is tracking the satellite, the integer number of cycles correctly accumulates the
change in range seen by the receiver. When a “lock break” occurs, this accumulated value can jump
an arbitrary integer number of cycles (this is called a cycle slip).
Checksum — by NMEA standard, a validity check performed on the data contained in the sentences,
calculated by the talker, appended to the message, then recalculated by the listener for comparison
to determine if the message was received correctly. Required for some sentences, optional for all
others.
Circular Error Probable (CEP) — the radius of a circle, centred at the user’s true location, that contains 50
percent of the individual position measurements made using a particular navigation system.
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GPS Glossary of Terms
Coarse Acquisition (C/A) Code — a spread spectrum direct sequence code that is used primarily by
commercial GPS receivers to determine the range to the transmitting GPS satellite. Uses a chip rate
of 1.023 MHz.
Communication protocol — a method established for message transfer between a talker and a listener which
includes the message format and the sequence in which the messages are to be transferred. Also
includes the signalling requirements such as bit rate, stop bits, parity, and bits per character.
Control segment — the Master Control Station and the globally dispersed reference Stations used to manage
the GPS satellites, determine their precise orbital parameters, and synchronize their clocks.
Course — the horizontal direction in which a vessel is to be steered or is being steered; the direction of travel
through the air or water. Expressed as angular distance from reference North (either true, magnetic,
compass, or grid), usually 000° (north), clockwise through 360°. Strictly, the term applies to
direction through the air or water, not the direction intended to be made good over the ground (see
track). Differs from heading.
Course Made Good (CMG) — the single resultant direction from a given point of departure to a subsequent
position; the direction of the net movement from one point to the other. This often varies from the
track caused by inaccuracies in steering, currents, cross-winds, etc. This term is often considered to
be synonymous with Track Made Good, however, track made good is the more correct term.
Course Over Ground (COG) — the actual path of a vessel with respect to the Earth (a misnomer in that
courses are directions steered or intended to be steered through the water with respect to a reference
meridian); this will not be a straight line if the vessel's heading yaws back and forth across the course.
Cross Track Error (XTE) — the distance from the vessel’s present position to the closest point on a great
circle line connecting the current waypoint coordinates. If a track offset has been specified in the
GPSCard SETNAV command, the cross track error will be relative to the offset track great circle
line.
Cycle Slip — when the carrier phase measurement jumps by an arbitrary number of integer cycles. It is
generally caused by a break in the signal tracking due to shading or some similar occurrence.
Dead Reckoning (DR) — the process of determining a vessel’s approximate position by applying from its last
known position a vector or a series of consecutive vectors representing the run that has since been
made, using only the courses being steered, and the distance run as determined by log, engine rpm,
or calculations from speed measurements.
Destination — the immediate geographic point of interest to which a vessel is navigating. It may be the next
waypoint along a route of waypoints or the final destination of a voyage.
Differential GPS (DGPS) — a technique to improve GPS accuracy that uses pseudorange errors at a known
location to improve the measurements made by other GPS receivers within the same general
geographic area.
Dilution of Precision (DOP) — a numerical value expressing the confidence factor of the position solution
based on current satellite geometry. The lower the value, the greater the confidence in the solution.
DOP can be expressed in the following forms.
GDOP
PDOP
-
estimated uncertainty for all parameters (latitude, longitude, height, clock offset)
estimated uncertainty for all 3D parameters (latitude, longitude, height)
-
HTDOP - estimated uncertainty for all time and 2D parameters (latitude, longitude, time)
HDOP
VDOP
TDOP
-
-
estimated uncertainty for all 2D parameters (latitude, longitude)
height is uncertain
-
clock offset is uncertain
Doppler — the change in frequency of sound, light or other wave caused by movement of its source relative
to the observer.
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GPS Glossary of Terms
Doppler aiding — a signal processing strategy, which uses a measured Doppler shift to help a receiver
smoothly track the GPS signal, to allow more precise velocity and position measurement.
Double-Difference — a position estimation mechanization which uses observations which are differenced
between receiver channels and between the reference and remote receivers.
Double-Difference Carrier Phase Ambiguity (or sometimes double difference ambiguity or ambiguity, for
short) — carrier phase ambiguities which are differenced between receiver channels and between the
reference and remote receivers. They are estimated when a double difference mechanism is used for
carrier phase positioning.
Earth-Centred-Earth-Fixed (ECEF) — a right-hand Cartesian coordinate system with its origin located at
the centre of the Earth. The coordinate system used by GPS to describe three-dimensional location.
ECEF — Earth-Centred-Earth-Fixed. This is a coordinate-ordinate system which has the X-coordinate in the
earth's equatorial plane pointing to the Greenwich prime meridian, the Z-axis pointing to the north
pole, and the Y-axis in the equatorial plane 90° from the X-axis with an orientation which forms a
right-handed XYZ system.
Ellipsoid — a smooth mathematical surface which represents the earth’s shape and very closely approximates
the geoid. It is used as a reference surface for geodetic surveys, see the PRTKA/B log in Appendix D,
Ellipsoidal Height — height above a defined ellipsoid approximating the surface of the earth.
Ephemeris — a set of satellite orbit parameters that is used by a GPS receiver to calculate precise GPS satellite
positions and velocities. The ephemeris is used in the determination of the navigation solution and
is updated periodically by the satellite to maintain the accuracy of GPS receivers.
Ephemeris Data — the data downlinked by a GPS satellite describing its own orbital position with time.
Epoch — same as measurement time epoch. The local time at which a GPSCard takes a measurement.
Field — a character or string of characters immediately preceded by a field delimiter.
Fixed Ambiguity Estimates — carrier phase ambiguity estimates which are set to a given number and held
constant. Usually they are set to integers or values derived from linear combinations of integers.
Fixed Discrete Ambiguity Estimates — carrier phase ambiguities which are set to values which are members
of a predetermined set of discrete possibilities, and then held constant.
Fixed field — a field in which the number of characters is fixed. For data fields, such fields are shown in the
sentence definitions with no decimal point. Other fields which fall into this category are the address
field and the checksum field (if present).
Fixed Integer Ambiguity Estimates — carrier phase ambiguities which are set to integer values and then held
constant.
Flash ROM — Programmable read-only memory.
Floating Ambiguity Estimates — ambiguity estimates which are not held to a constant value, but are allowed
to gradually converge to the correct solution.
GDOP — Geometric Dilution of Precision - A numerical value expressing the confidence factor of the position
solution based on current satellite geometry. Assumes that 3D position (latitude, longitude, height)
and receiver clock offset (time) are variables in the solution. The lower the GDOP value, the greater
the confidence in the solution.
Geoid — the shape of the earth if it were considered as a sea level surface extended continuously through the
continents. The geoid is an equipotential surface coincident with mean sea level to which at every
point the plumb line (direction in which gravity acts) is perpendicular. The geoid, affected by local
Geodetic datum — the reference ellipsoid surface that defines the coordinate system.
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GPS Glossary of Terms
Geostationary — a satellite orbit along the equator that results in a constant fixed position over a particular
reference point on the earth’s surface. (GPS satellites are not geostationary.)
Global Positioning System (GPS) — full name NAVSTAR Global Positioning System, a space-based radio
positioning system which provides suitably equipped users with accurate position, velocity and time
data. When fully operational, GPS will provide this data free of direct user charge worldwide,
continuously, and under all weather conditions. The GPS constellation will consist of 24 orbiting
satellites, four equally spaced around each of six different orbiter planes. The system is being
developed by the Department of Defence under U.S. Air Force management.
Great circle — the shortest distance between any two points along the surface of a sphere or ellipsoid, and
therefore the shortest navigation distance between any two points on the Earth. Also called Geodesic
Line.
HDOP — Horizontal Dilution of Precision - A numerical value expressing the confidence factor of the
horizontal position solution based on current satellite geometry. Makes no constraint assumptions
about time, and about height only if the FIX HEIGHT command has been invoked. The lower the
HDOP value, the greater the confidence in the solution.
HTDOP — Horizontal position and Time Dilution of Precision - A numerical value expressing the confidence
factor of the position solution based on current satellite geometry. Assumes height is known if the
FIX HEIGHT command has been invoked. If not, it will give the normalized precision of the
horizontal and time parameters given that nothing has been constrained. The lower the HTDOP
value, the greater the confidence factor.
Heading — the direction in which a vessel points or heads at any instant, expressed in degrees 000° clockwise
through 360° and may be referenced to True North, Magnetic North, or Grid North. The heading of
a vessel is also called the ship's head. Heading is a constantly changing value as the vessel oscillates
or yaws across the course due to the effects of the air or sea, cross currents, and steering errors.
Integer Ambiguity Estimates — carrier phase ambiguity estimates which are only allowed to take on integer
values.
Iono-free Carrier Phase Observation — a linear combination of L1 and L2 carrier phase measurements
which provides an estimate of the carrier phase observation on one frequency with the effects of the
ionosphere removed. It provides a different ambiguity value (non-integer) than a simple
measurement on that frequency.
Kinematic — the user’s GPS antenna is moving. In GPS, this term is typically used with precise carrier phase
positioning, and the term dynamic is used with pseudorange positioning.
L1 frequency — the 1575.42 MHz GPS carrier frequency which contains the course acquisition (C/A) code,
as well as encrypted P-code, and navigation messages used by commercial GPS receivers.
L2 frequency — a secondary GPS carrier, containing only encrypted P-code, used primarily to calculate signal
delays caused by the ionosphere. The L2 frequency is 1227.60 MHz.
Lane — a particular discrete ambiguity value on one carrier phase range measurement or double difference
carrier phase observation. The type of measurement is not specified (L1, L2, L1-L2, iono-free)
Local Observation Set — an observation set, as described below, taken by the receiver on which the software
is operating as opposed to an observation taken at another receiver (the reference station) and
transmitted through a radio link.
Local Tangent Plane — a coordinate system based on a plane tangent to the ellipsoid’s surface at the user’s
location. The three coordinates are east, north and up. Latitude, longitude and height positions
operate in this coordinate system.
Low-latency Solution — a position solution which is based on a prediction. A model (based on previous
reference station observations) is used to estimate what the observations will be at a given time
epoch. These estimated reference station observations are combined with actual measurements
taken at the remote station to provide a position solution.
Magnetic bearing — bearing relative to magnetic north; compass bearing corrected for deviation.
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GPS Glossary of Terms
Magnetic heading — heading relative to magnetic north.
Magnetic variation — the angle between the magnetic and geographic meridians at any place, expressed in
degrees and minutes east or west to indicate the direction of magnetic north from true north.
Mask angle — the minimum GPS satellite elevation angle permitted by a particular receiver design. Satellites
below this angle will not be used in position solution.
Matched Observation Set Pair — it contains observations from both the reference station and the local
receiver which have been matched by time epoch, contain the same satellites, and are corrected for
any known offsets.
Measurement error variance — the square of the standard deviation of a measurement quantity. The standard
deviation is representative of the error typically expected in a measured value of that quantity.
Measurement Time Epoch — the local time at which a GPSCard takes a measurement.
Multipath errors — GPS positioning errors caused by the interaction of the GPS satellite signal and its
reflections.
-9
Nanosecond — 1 × 10 second
Nautical mile — any of various units of distance for sea and air navigation; in the U.S. since 1959, an
international unit of linear measure equal to 1 minute of arc of a great circle of the Earth, 1,852
metres (6,076 feet).
Non-Volatile Memory — a type of memory device that retains data in the absence of a power supply.
Null field — by NMEA standard, indicates that data is not available for the field. Indicated by two ASCII
commas, i.e., ",," (HEX 2C2C), or, for the last data field in a sentence, one comma followed by either
the checksum delimiter "*" (HEX 2A) or the sentence delimiters <CR><LF> (HEX 0D0A). [Note:
the ASCII Null character (HEX 00) is not to be used for null fields.]
Obscuration — term used to describe periods of time when a GPS receiver’s line-of-sight to GPS satellites is
blocked by natural or man-made objects.
Observation — an input to an estimation algorithm. The two observations used in NovAtel’s RTK algorithms
are the pseudorange measurement and the carrier phase measurement.
Observation Set — a set of GPSCard measurements taken at a given time which includes one time for all
measurements, and the following for each satellite tracked: PRN number, pseudorange or carrier
phase or both, lock time count, signal strength, and tracking status. Either L1 only or L1 and L2
measurements are included in the set. The observation set is assumed to contain information
indicating how many satellites it contains and which ones have L1-only and which ones have L1/L2
pairs.
Origin waypoint — the starting point of the present navigation leg, expressed in latitude and longitude.
Parallel receiver — a receiver that monitors four or more satellites simultaneously with independent channels.
P-Code (precise or protected) — a spread spectrum direct sequence code that is used primarily by military
GPS receivers to determine the range to the transmitting GPS satellite. Uses a chipping rate of 10.23
MHz.
PDOP — Position Dilution of Precision. This is related to GDOP. It describes the effects of geometry on 3
dimensional positioning accuracy. It is defined to be the square root of the sum of the three diagonals
of a normalized (assume measurement noise = 1) covariance matrix which correspond to position
error.
Pitch — the rising and falling of the bow and stern of a ship in a rough sea or the movement up or down of the
nose and tail of an airplane.
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GPS Glossary of Terms
Precise Positioning Service (PPS) — the GPS positioning, velocity, and time service which will be available
on a continuous, worldwide basis to users authorized by the U.S. Department of Defence (typically
using P-Code).
PRN number — a number assigned by the GPS system designers to a given set of pseudorandom codes.
Typically, a particular satellite will keep its PRN (and hence its code assignment) indefinitely, or at
least for a long period of time. It is commonly used as a way to label a particular satellite.
Pseudolite — an Earth-based transmitter designed to mimic a satellite. May be used to transmit differential
corrections.
Pseudorange — the calculated range from the GPS receiver to the satellite determined by taking the difference
between the measured satellite transmit time and the receiver time of measurement, and multiplying
by the speed of light. This measurement generally contains a large receiver clock offset error.
Pseudorange Measurements — measurements made using one of the pseudorandom codes on the GPS
signals. They provide an unambiguous measure of the range to the satellite including the effect of
the satellite and user clock biases.
Receiver channels — a GPS receiver specification which indicates the number of independent hardware
signal processing channels included in the receiver design.
Reference Satellite — in a double difference implementation, measurements are differenced between different
satellites on one receiver in order to cancel the clock bias effect. Usually one satellite is chosen as
the “reference”, and all others are differenced with it.
Reference Station — the GPS receiver which is acting as the stationary reference. It has a known position and
transmits messages for the "remote" receiver to use to calculate its position.
Relative bearing — bearing relative to heading or to the vessel.
Remote Receiver — the GPS receiver which does not know its position and needs to receive measurements
from a reference station to calculate differential GPS positions. (The terms remote and rover are
interchangeable.)
Residual — in the context of measurement, the residual is the misclosure between the calculated
measurements, using the position solution and actual measurements.
RMS — root-mean-square, a probability level of 66%.
Roll — to move by turning on an axis or to rotate about its axis lengthwise, as an aircraft in flight.
Route — a planned course of travel, usually composed of more than one navigation leg.
Rover Receiver — the GPS receiver which does not know its position and needs to receive measurements from
a reference station to calculate differential GPS positions. (The terms rover and remote are
interchangeable.)
RT-20 — NovAtel’s Double Differencing Technology for real-time kinematic (RTK) carrier phase floating
ambiguity resolution.
RTCA — Radio Technical Commission for Aeronautics, an organization which developed and defined a
RTCM — Radio Technical Commission for Maritime Services, an organization which developed and defined
the SC-104 message format for differential positioning. See Appendix F for further information.
RTK — real-time kinematic, a type of differential positioning based on observations of carrier phase. In this
document it is also used with reference to RT-2 and RT-20.
Satellite elevation — the angle of the satellite above the horizon.
Selected waypoint — the waypoint currently selected to be the point toward which the vessel is travelling.
Also called "to" waypoint, destination or destination waypoint.
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GPS Glossary of Terms
Selective Availability (SA) — the method used by the United States Department of Defence to control access
to the full accuracy achievable by civilian GPS equipment (generally by introducing timing and
ephemeris errors).
Sequential receiver — a GPS receiver in which the number of satellite signals to be tracked exceeds the
number of available hardware channels. Sequential receivers periodically reassign hardware
channels to particular satellite signals in a predetermined sequence.
Spherical Error Probable (SEP) — the radius of a sphere, centred at the user’s true location, that contains
50 percent of the individual three-dimensional position measurements made using a particular
navigation system.
Spheroid — sometimes known as ellipsoid; a perfect mathematical figure which very closely approximates
the geoid. Used as a surface of reference for geodetic surveys. The geoid, affected by local gravity
disturbances, is irregular.
Standard Positioning Service (SPS) — a positioning service made available by the United States Department
of Defence which will be available to all GPS civilian users on a continuous, worldwide basis
(typically using C/A Code).
SV — Space Vehicle ID, sometimes used as SVID; also used interchangeably with Pseudo-Random Noise
Number (PRN).
Static — the user’s GPS antenna does not move.
TDOP — Time Dilution of Precision - A numerical value expressing the confidence factor of the position
solution based on current satellite geometry. The lower the TDOP value, the greater the confidence
factor.
Three-dimensional coverage (hours) — the number of hours-per-day when four or more satellites are
available with acceptable positioning geometry. Four visible satellites are required to determine
location and altitude.
Three-dimensional (3D) navigation — navigation mode in which altitude and horizontal position are
determined from satellite range measurements.
Time-To-First-Fix (TTFF) — the actual time required by a GPS receiver to achieve a position solution. This
specification will vary with the operating state of the receiver, the length of time since the last
position fix, the location of the last fix, and the specific receiver design.
Track — a planned or intended horizontal path of travel with respect to the Earth rather than the air or water.
The track is expressed in degrees from 000° clockwise through 360° (true, magnetic, or grid).
Track made good — the single resultant direction from a point of departure to a point of arrival or subsequent
position at any given time; may be considered synonymous with Course Made Good.
True bearing — bearing relative to true north; compass bearing corrected for compass error.
True heading — heading relative to true north.
Two-dimensional coverage (hours) — the number of hours-per-day with three or more satellites visible.
Three visible satellites can be used to determine location if the GPS receiver is designed to accept an
external altitude input.
Two-dimensional (2D) navigation — navigation mode in which a fixed value of altitude is used for one or
more position calculations while horizontal (2D) position can vary freely based on satellite range
measurements.
Undulation — the distance of the geoid above (positive) or below (negative) the mathematical reference
ellipsoid (spheroid). Also known as geoidal separation, geoidal undulation, geoidal height.
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GPS Glossary of Terms
Universal Time Coordinated (UTC) — this time system uses the second-defined true angular rotation of the
Earth measured as if the Earth rotated about its Conventional Terrestrial Pole. However, UTC is
adjusted only in increments of one second. The time zone of UTC is that of Greenwich Mean Time
(GMT).
Update rate — the GPS receiver specification which indicates the solution rateprovided by the receiver when
operating normally.
VDOP — Vertical Dilution of Precision. This is related to GDOP. It describes the effects of geometry on
vertical positioning accuracy. It is defined to be the square root of the diagonal of a normalized
(assume measurement noise = 1) covariance matrix which corresponds to vertical position error.
Variable field — by NMEA standards, a data field which may or may not contain a decimal point and which
may vary in precision following the decimal point depending on the requirements and the accuracy
of the measuring device.
WGS84 — World Geodetic System 1984 is an ellipsoid designed to fit the shape of the entire Earth as well as
possible with a single ellipsoid. It is often used as a reference on a worldwide basis, while other
ellipsoids are used locally to provide a better fit to the Earth in a local region. GPS uses the centre
of the WGS84 ellipsoid as the centre of the GPS ECEF reference frame.
Waypoint — a reference point on a track.
Wide Lane — a particular integer ambiguity value on one carrier phase range measurement or double
difference carrier phase observation when the difference of the L1 and L2 measurements is used. It
is a carrier phase observable formed by subtracting L2 from L1 carrier phase data: Φ' = Φ1 - Φ2. The
corresponding wavelength is 86.2 cm
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GPS Glossary of Acronyms
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GPS GLOSSARY OF ACRONYMS
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GPS GLOSSARY OF ACRONYMS
1PPS
2D
2DRMS
3D
One Pulse Per Second
Two Dimensional
Twice distance RMS
Three Dimensional
A/D
Analog-to-Digital
ADR
AGC
ASCII
Accumulated Doppler Range
Automatic Gain Control
American Standard Code for Information Interchange
BIH
BIST
bps
Bureau l’International de l’Heure
Built-In-Self-Test
Bits per Second
C/A Code
CEP
C/No
CPU
CR
Coarse/Acquisition Code
Circular Error Probable
Carrier to Noise Density Ratio
Central Processing Unit
Carriage Return
CRC
CTP
CTS
CTS
Cyclic Redundancy Check
Conventional Terrestrial Pole
Conventional Terrestrial System
Clear To Send
dB
Decibel
DCE
DGNSS
DGPS
DOP
DSP
Data Communications Equipment
Differential Global Navigation Satellite System
Differential Global Positioning System
Dilution Of Precision
Digital Signal Processor
Data Set Ready
DSR
DTR
Data Terminal Ready
ECEF
EGNOS
EMC
EMI
Earth-Centred-Earth-Fixed
European Geostationary Navigation Overlay Service
Electromagnetic Compatibility
Electromagnetic Immunity
ESD
Electrostatic Discharge
FEC
FIA
FIFO
Forward Error Correction
US Federal Aviation Administration
First In First Out
GDOP
GMT
GND
GPS
Geometric Dilution Of Precision
Greenwich Mean Time
Ground
Global Positioning System
HDOP
hex
Horizontal Dilution Of Precision
Hexadecimal
HTDOP
Hz
Horizontal position and Time Dilution Of Precision
Hertz
IC
IF
IGRF
I/O
Integrated Circuit
Intermediate Frequency
International Geomagnetic Reference Field
Input/Output
IODE
IRQ
Issue of Data (Ephemeris)
Interrupt Request
LF
Line Feed
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GPS Glossary of Acronyms
LHCP
LNA
LO
Left Hand Circular Polarization
Low Noise Amplifier
Local Oscillator
lsb
Least significant bit
MET
MEDLL
MKI
MKO
MSAS
msb
Multipath Elimination Technology
Multipath Estimation Delay Lock Loop
Mark In
Mark Out
Multi-Functional Transport Satellite (MTSAT) based Augmentation System
Most significant bit
msec
millisecond
MSL
Mean sea level
N. mi.
NAVSTAR
NCO
NMEA
ns
Nautical mile
NAVigation Satellite Timing And Ranging (synonymous with GPS)
Numerically Controlled Oscillator
National Marine Electronics Association
nanosecond
OCXO
OEM
Oven Controlled Crystal Oscillator
Original Equipment Manufacturer
PC
Personal Computer
Precise Code
Position Dilution Of Precision
Phase Lock Loop
P Code
PDOP
PLL
PPS
PRN
Precise Positioning Service or Pulse Per Second
PseudoRandom Noise number
RAM
RF
RHCP
ROM
RTCA
RTCM
RTK
Random Access Memory
Radio Frequency
Right Hand Circular Polarization
Read Only Memory
Radio Technical Commission for Aviation Services
Radio Technical Commission for Maritime Services
Real Time Kinematic
RTS
RXD
Request To Send
Received Data
SA
Selective Availability
Special Category I
Spherical Error Probable
Signal-to-Noise Ratio
Standard Positioning Service
Space Vehicle
SCAT-I
SEP
SNR
SPS
SV
SVN
Space Vehicle Number
TCXO
TDOP
TTFF
TTL
Temperature Compensated Crystal Oscillator
Time Dilution Of Precision
Time-To-First-Fix
Transistor Transistor Logic
Transmitted Data
TXD
UART
UDRE
UTC
Universal Asynchronous Receiver Transmitter
User Differential Range Error
Universal Time Coordinated
VARF
Variable Frequency
VCTCXO
VDOP
Voltage Controlled Temperature Compensated Crystal Oscillator
Vertical Dilution of Precision
WAAS
WGS
wpt
Wide Area Augmentation System
World Geodetic System
Waypoint
XTE
Crosstrack Error
MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 1
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M
Index
clock 33, 37, 42, 53, 56, 59, 63, 65, 67–72, 83, 94–98, 128, 147, 193, 197, 218, 220, 241, 263–264, 267
com
command
D
differential
corrections 14, 30, 33, 34, 47, 50–51, 53, 69, 70, 71, 79, 90, 97, 98, 109, 121, 123, 179, 222, 234, 241, 267
direction
E
MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 1
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M
Index
K
L
M
N
navigation 11, 46, 47, 53, 56, 59, 62, 99, 112, 126, 163, 166, 167, 173, 175, 181, 202, 204, 262, 264, 266–268
noise 25, 27, 38, 41, 67, 72, 77, 81, 88, 94, 95, 149, 155, 164, 193, 194, 213, 233, 244, 245, 248, 250, 252, 253,
O
P
MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 1
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M
Index
pseudorange 36, 50, 53–55, 56, 59, 65–74, 77, 88, 97, 98, 125, 164, 179, 193, 197, 218, 228, 233, 267
R
receiver 14, 19, 24, 32, 33, 35, 37, 45, 47, 51–52, 55, 56, 59, 62–63, 65, 74, 77–78, 83, 89, 93, 97–99, 112, 123,
125, 141, 147, 158, 160, 163, 167, 178, 179, 181, 191, 192, 193, 196, 197, 198, 202, 205, 210, 220, 221,
reference station 19, 23, 26, 28, 32, 42, 45, 46, 48, 52–55, 68, 72, 74, 90, 97, 98, 109, 115, 118, 121, 123, 141, 179,
remote station 19–20, 42, 45, 47, 48, 50, 51, 53, 54, 65, 67, 70–72, 88–90, 98, 115, 116, 118, 121, 141, 233, 265
RF
S
satellite 15, 18, 26, 28, 31–33, 45, 46, 48, 51–53, 55, 56, 59, 62, 73–75, 82, 88, 94, 98, 99, 101, 111, 116, 118, 124,
129, 131, 136, 153, 159, 162, 181, 186, 192, 193, 197, 204, 210, 212, 214, 218, 230, 233, 246, 248, 262,
segment
274
MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 1
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OM-20000041
Rev 1
98/11/03
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