Garmin GPS Receiver 188C User Manual

®
GPSMAP 188/188C Sounder  
chartplotting receiver  
owner’s manual  
(GPSMAP 188C shown)  
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INTRODUCTION > ABOUT THIS MANUAL  
The Basic Operation section provides you with detailed  
information and step-by-step directions for features such as using  
the Find Menu, navigating a route, and using waypoints.  
INTRODUCTION  
®
®
Thank you for choosing the Garmin GPSMAP 188/188C  
Sounder. Take a moment now to compare the contents of this  
package with the packing list on the outside of the box. If any  
pieces are missing, contact your Garmin dealer immediately.  
The Main Pages section provides detailed explanations about  
each page in the GPSMAP 188/188C Sounder and step-by-step  
directions on using the pages.  
Before you begin working with the GPSMAP 188/188C Sounder,  
review the installation instructions listed in the Appendix. If  
you have any question about installing your chartplotter, contact  
Garmin Product Support or a professional installer.  
The Main Menu section provides detailed explanations about the  
Main Menu and how to use it to configure your unit.  
The Using Sonar section contains information on the sonar  
capablities.  
The GPSMAP 188/188C Sounder Quick Reference Guide contains  
helpful tips on using the unit and performing various navigation  
tasks. It is a good idea to keep the Quick Reference Guide nearby  
whenever you are operating your new GPSMAP 188/188C  
Sounder.  
The Appendix contains installation instructions, specifications,  
optional accessories, and maintenance information. You can also  
find warranty and FCC information in the Appendix. Read the  
Safety Information to learn how to install and use your Garmin  
GPSMAP 188/188C Sounder safely and responsibly.  
About This Manual  
To get the most out of your new navigation system, take time to  
read this manual and learn the operating procedures for your unit in  
detail. This manual is organized into the following sections.  
An Index is provided at the end of the manual for reference.  
The Introduction section contains the Table of Contents and  
GPSMAP 188/188C Sounder care information.  
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INTRODUCTION > TABLE OF CONTENTS  
Table of Contents  
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INTRODUCTION > TABLE OF CONTENTS  
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INTRODUCTION > CARE INFORMATION  
Immersing the Unit in Water  
Care Information  
The GPSMAP 188/188C Sounder is waterproof to IEC Standard  
60529 IPX7. It can withstand immersion in 1 meter of water for 30  
minutes. Prolonged submersion can cause damage to the unit. After  
submersion, be certain to wipe and air dry the unit before reuse.  
Cleaning the Unit  
The GPSMAP 188/188C Sounder is constructed of high quality  
materials and does not require user maintenance other than  
cleaning. Clean the unit using a cloth dampened with a mild  
detergent solution and then wipe dry. Avoid chemical cleaners and  
solvents that can damage plastic components.  
To resolve problems that cannot be remedied using this manual,  
contact Garmin Product Support in the U.S.A. at 800/800-1020 or  
Garmin Europe at 44/0870-8501241.  
Storing the GPSMAP 188/188C Sounder  
Do not store the GPSMAP 188/188C Sounder where prolonged  
exposure to temperature extremes can occur (such as in the trunk  
of a car) as permanent damage can result. User information, such  
as waypoints and routes are retained in the unit’s memory without  
the need for external power. It is always a good practice to back up  
important user data by manually recording it or downloading it to a  
PC (transferring it to MapSource.)  
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BASIC OPERATION > INITIALIZING THE RECEIVER  
BASIC OPERATION  
Initializing the Receiver  
The first time you turn on the GPSMAP 188/188C Sounder, the  
receiver must be given an opportunity to collect satellite data  
and establish its present location. To ensure proper initialization,  
the GPSMAP 188/188C Sounder is shipped from the factory in  
AutoLocate Mode.  
Before you initialize, make sure the GPSMAP 188/188C Sounder  
unit and antenna are correctly installed on your vessel according to  
the instructions in the Appendix. Install the antenna in a location  
with a clear and unobstructed view of the sky.  
To turn on the GPSMAP 188/188C Sounder:  
1. Press and hold the POWER key until the power tone  
sounds, and then release the POWER key. The Warning  
Page appears while the unit conducts a self-test.  
A full-screen GPS Information Page appears after you press  
ENTER to acknowledge the Warning Page. The page goes away  
after the unit gets a position fix or you press either ENTER or  
QUIT. The page can be disabled and enabled on the  
Main Menu—Pages tab (see page 63).  
2. When the self-test is complete, press ENTER to agree and  
acknowledge the warning.  
The GPS Information Page appears as the receiver begins acquiring  
satellites.  
To turn off the GPSMAP 188/188C Sounder:  
1. Press and hold the POWER key for approximately  
2 seconds, until the screen is blank.  
2. When the screen is blank, release the POWER key.  
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BASIC OPERATION > INITIALIZING THE RECEIVER  
To graphically initialize the GPSMAP 188/188C Sounder:  
1. Press MENU twice for the Main Menu. Press up or down  
on the ROCKER until the GPS tab is highlighted, and then  
press MENU once.  
2. Using the ROCKER, highlight Initialize Position, and press  
ENTER. The Initialize Position Page appears, prompting  
you to select your approximate location with the map  
pointer.  
3. Use the ROCKER to move the map pointer to your  
approximate location within 200 miles. If you have difficulty  
identifying your location, press and release the IN key to  
see the next lower map range.  
The unit now begins searching for the appropriate satellites for  
your region and should acquire a fix within a few minutes. When  
viewing the GPS tab on the Main Menu, a signal strength bar for  
each satellite in view appears on the bottom of the page, with the  
appropriate satellite number under each bar.  
4. After you determine your approximate location on the map,  
press ENTER.  
NOTE: This does not calibrate the unit in any way, but rather  
helps to speed up the initial satellite acquisition. If the unit  
displays “Ready 2D or 3D” during this process, it is not  
necessary to initialize the unit.  
No signal strength bars—the receiver is looking for the  
satellites indicated.  
Hollow signal strength bars—the receiver has found the  
indicated satellite(s) and is collecting data.  
Solid signal strength bars—the receiver is ready to use.  
When the receiver has collected information from at least three  
satellites, the top of the screen displays either “Ready 2D or 3D”,  
and the GPSMAP 188/188C Sounder is ready for use.  
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BASIC OPERATION > SIMULATOR MODE  
Simulator Mode  
Simulator Mode turns the GPS receiver off for use indoors or  
practice. Any of the functions discussed in the following pages  
can be performed in Simulator Mode. While in Simulator Mode, a  
“Running Simulator” message appears after 2 minutes of inactivity.  
Keep in mind that the GPSMAP 188/188C Sounder does not  
track satellites in Simulator Mode, and this mode should never be  
used for actual navigation. All the waypoint and route planning  
completed in Simulator Mode is retained in memory for future use.  
NOTE: Do not attempt to navigate using Simulator Mode.  
When the unit is set to Simulator Mode, the GPS receiver is  
turned off. Any satellite signal strength bars displayed are only  
simulations and do not represent the strength of actual satellite  
signals.  
To place the GPSMAP 188/188C Sounder in  
Simulator Mode:  
1. Press MENU twice to display the Main Menu. Press up or  
down on the ROCKER until the GPS tab is highlighted, and  
press MENU once.  
2. Use the ROCKER to highlight Start Simulator, and press  
ENTER. Choose No to the retail demonstration, and press  
ENTER.  
3. Press ENTER to confirm the Running Simulator message  
that appears at the bottom of the display. “Simulating”  
appears at the top of each of the Main pages.  
4. To turn off the Simulator Mode, press MENU and select  
Stop Simulator.  
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BASIC OPERATION > ADJUSTING THE BACKLIGHT  
To adjust the simulated speed and heading from the  
Pointer or Highway Pages:  
1. Press up on the ROCKER increase the speed in  
10 knot/kph/mph increments. Press down on the ROCKER  
to decrease the speed in the same increments.  
The Set Position,  
Track Control, Track  
and Speed fields  
only show while in  
Simulator Mode.  
2. Press left and right on the ROCKER to steer the boat.  
Adjusting the Backlight  
The Sounder’s adjustable screen backlighting is controlled with the  
POWER key, and can be adjusted from any page.  
To enter a simulated speed and heading from the  
Main Menu:  
1. Press MENU twice to display the Main Menu.  
2. Use the ROCKER to highlight the Systm tab, press  
right then down until the field below the word Speed is  
highlighted, then press ENTER.  
To adjust the backlight:  
1. Press and release the POWER key. The adjustment slider  
3. Use the ROCKER to enter a speed, and press ENTER.  
window appears.  
4. Use the ROCKER to highlight Track Control. Press  
ENTER, and select a heading.  
2. Press the POWER key again to start the user-defined  
backlight level. To adjust this level, press up or down on  
the ROCKER. If you press POWER one more time, the  
backlight is at the maximum setting.  
5. Press ENTER to finish, and QUIT until you return to the  
Map Page.  
3. Press ENTER or QUIT when finished.  
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BASIC OPERATION > INTERFACE KEYS  
Interface Keys  
NAV Key  
IN/OUT Zoom Keys  
Press and release at any time to view the  
Navigation menu.  
From the Map Page, press to zoom in or out.  
From any other page, press to scroll up or  
down a list.  
QUIT Key  
PAGE Key  
Press and release to cancel data entry or  
exit a page.  
Press to cycle through the Main pages.  
ROCKER Key  
Press to end an operation in progress and  
return to the main page.  
Press up/down or right/left to move through  
lists, highlight fields, on-screen buttons and  
icons, enter data, or move the map pointer.  
MENU Key  
Press and release to view options for a page.  
Press twice to view the Main Menu.  
FIND Key  
Press to search for points such as user  
waypoints, cities, and services.  
ENTER/MARK Key  
Press and release to enter highlighted options  
POWER Key  
and data or confirm on-screen messages.  
Press and hold to turn unit on or off.  
Press and release to adjust backlighting.  
Press and hold at any time to mark your  
current location as a waypoint.  
MOB Key  
Press and hold for MOB (Man OverBoard).  
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BASIC OPERATION > ENTERING DATA AND SELECTING OPTIONS  
Some pages contain on-screen buttons. As shown below, the New  
Waypoint window has three buttons: Map, Delete, and OK. To  
activate, highlight the a button, and press ENTER.  
Entering Data and Selecting Options  
You can select and start options, and enter data to customize the  
GPSMAP 188/188C Sounder to fit your requirements. Use the  
ENTER key and the ROCKER to select options, enter names and  
numbers in data fields, and activate your selections.  
To select and start optional feature:  
1. With any page displayed, press MENU to display the  
options menu. The options menu displays a list of optional  
features that are specific for that page. To select an option  
requires movement of the pointer. This is referred to as  
highlighting, selecting, or choosing an item.  
On-Screen Buttons  
2. Use the ROCKER to move the cursor (highlight) up and  
down a list or up, down, left, and right on menus.  
3. After you have highlighted a selection, press ENTER to  
either activate the feature or press MENU to display a  
sub-menu or list with more options. Repeat this process to  
select an option from the list, or press QUIT to return to the  
previous setting.  
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BASIC OPERATION > USING THE MAP POINTER  
To pan the map:  
1. Use the IN/OUT keys to select a map range.  
Using the Map Pointer  
Working from the Map Page centers around the use of the pointer.  
Controlled by the ROCKER, the pointer is used to pan to map  
locations, mark and edit waypoints and routes, and review position  
data of on-screen map items and waypoints. When you move the  
pointer over a map item, a highlighted description of that item  
appears.  
2. Use the ROCKER to move the pointer. A data field appears  
at the top of the display showing the bearing and distance  
from your boat to the pointer, along with the latitude/  
longitude of the pointer.  
3. Press QUIT to re-center your boat on the map display.  
Distance  
Bearing  
Pointer  
Coordinates  
Current  
Location  
Map Pointer  
Map Range  
The map display actively scrolls or pans, enabling you to explore  
areas around the world and create waypoints and routes. Pressing  
QUIT returns the map to your present location.  
NOTE: When the pointer reaches the edge of the map, the unit  
can pause as it loads new map data.  
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BASIC OPERATION > CREATING AND USING WAYPOINTS  
ENTER/MARK Key  
Creating and Using Waypoints  
The Garmin GPSMAP 188/188C Sounder stores up to 3,000  
alphanumeric waypoints with a user-defined symbol, comments,  
and depth available for each waypoint. Waypoints can be created  
using two basic methods:  
The Garmin GPSMAP 188/188C Sounder’s ENTER/MARK key  
quickly captures your present location to create a new waypoint.  
The unit must have a valid position (2D or 3D) fix to mark your  
present position. You can also use this option to manually enter  
waypoint coordinates.  
ENTER/MARK Key—marks your present location, and provides  
options to select a map location or map item from the map display.  
Also, you can enter a new waypoint’s location coordinates  
manually.  
To mark your present position:  
1. Press and hold ENTER/MARK until the New Waypoint  
window appears. A default three-digit name and symbol is  
created for the new waypoint.  
Graphically—defines a new waypoint location from the map  
display using the ROCKER.  
2. To accept the waypoint with the default name and symbol,  
highlight OK, and press ENTER.  
3. To enter a different name, highlight the name field, and  
press ENTER. Use the ROCKER to enter the new letter/  
numbers, and press ENTER when finished. You can use up  
to 10 characters for the name.  
4. To select a different symbol, highlight the symbol field to the  
left of the name, and press ENTER. Use the ROCKER to  
highlight the new symbol, and press ENTER.  
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BASIC OPERATION > CREATING AND USING WAYPOINTS  
5. To enter optional comments or a depth, highlight the  
Comments or Depth field to the right of the location  
coordinates, and press ENTER, use the ROCKER to enter  
a value, and press ENTER.  
To create a new waypoint graphically:  
1. Use the ROCKER to move the pointer to a map location. If  
you want to create the new waypoint at an on-screen map  
item, highlight the map item on the display.  
6. To manually enter a set of coordinates, highlight the  
coordinates, and press ENTER, use the ROCKER to enter  
the new coordinates, and press ENTER when finished.  
2. Press and release ENTER/MARK to capture the pointer  
location. Do not hold the button down, doing so marks your  
present location, not the map location.  
7. Use the ROCKER to highlight OK. When finished, press  
ENTER to save the waypoint into memory.  
If you are not using a map item to create a waypoint, go to  
step 4.  
3. Highlight Create Wpt or OK, and press ENTER.  
Creating Waypoints Graphically  
4. To accept the waypoint with the default name and symbol,  
You create waypoints graphically from the map display. To mark  
a map location or map item, select the location or item with the  
pointer, and press ENTER/MARK. When selecting a location or  
map item, a description of the point, its distance and bearing from  
your current location, and the latitude/longitude of the pointer is  
displayed along the top of the map.  
press ENTER.  
5. To change the name, symbol, or add a comment or depth,  
highlight the appropriate field, and press ENTER. Make  
your changes and press ENTER when finished.  
6. Move the highlight back to OK, and press ENTER to confirm  
the changes.  
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BASIC OPERATION > MAN OVERBOARD (MOB)  
When a MOB is active, a MOB waypoint with an international  
MOB symbol is created and the unit is on an active navigation to  
that point. Use any of the Navigation Pages to guide you back to  
the MOB point. The MOB waypoint is stored in the waypoint list  
and works like any other waypoint.  
Man OverBoard (MOB)  
The GPSMAP 188/188C Sounder’s Man OverBoard (MOB)  
function simultaneously marks and sets a course back to the  
marked location for quick response to emergency situations.  
The MOB function allows you to quickly activate  
navigation back to a location.  
To stop navigation, highlight  
Stop Navigation and press ENTER.  
To activate the MOB function:  
1. Press the MOB key.  
2. Press ENTER to begin navigating to the MOB location.  
3. To stop navigation to the MOB location, press NAV,  
highlight Stop Navigation, and press ENTER.  
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BASIC OPERATION > REVIEWING AND EDITING WAYPOINTS  
3. From the Waypoint Edit Page, change the name, symbol,  
comment, location coordinates, or depth for the selected  
waypoint. When finished, highlight Next, and press ENTER  
to save them, or press QUIT.  
Reviewing and Editing Waypoints  
Waypoints are reviewed, modified, renamed, moved, or deleted at  
any time through the Waypoint Edit Page. The Waypoint Edit Page  
is available for any stored waypoint. Select the waypoint on the  
map or from the waypoint list on the Main Menu—Points tab.  
Symbol  
Name  
Coordinates  
Comment  
Sub Tabs  
Depth  
Waypoint List  
Waypoint Edit Page  
To change the waypoint name:  
1. Highlight the waypoint name field, and press ENTER.  
To access the Waypoint Edit Page:  
1. Use the ROCKER to highlight the waypoint on the map  
display.  
2. Use the ROCKER to enter a new name, and press ENTER.  
Or  
Press MENU twice, highlight the Points tab, and choose a  
waypoint from the User or Proximity waypoint lists.  
2. Press ENTER to display the Waypoint Edit Page.  
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BASIC OPERATION > NAVIGATING TO A DESTINATION  
To change the waypoint symbol:  
1. Highlight the waypoint symbol field to the left of the  
Navigating to a Destination  
Using the Nav Key  
waypoint name, and press ENTER.  
The NAV key provides three ways to navigate to a destination:  
Go To Point, Follow Route, and Follow Track (TracBack). When  
you are actively navigating, the Map Page displays a straight line  
from your current location to the destination. The Go To option is  
the easiest method for selecting a destination. A Go To allows you  
to select a destination point and quickly set a direct course from  
your present location. If you have a point highlighted on a list or  
the map, Go To <point name> appears in addition to Go To Point.  
The Go To function is accessed from any list of points or  
graphically from the Map Page.  
2. Use the ROCKER to select a new symbol, and press  
ENTER.  
To change the Comment, Location, Coordinates,  
or Depth:  
1. Highlight a field, and press ENTER.  
2. Use the ROCKER to edit or enter the data. To move to the  
next line, press right on the ROCKER.  
3. Press ENTER when finished.  
To move the waypoint on the map:  
1. From the Waypoint Edit Page, highlight Show Map, and  
press ENTER.  
2. Highlight the waypoint, and press ENTER. A MOVE label  
now appears under the pointer arrow in addition to a  
distance, bearing, and coordinate window. You can also  
use the IN and OUT keys to zoom the map. The map range  
appears in the lower right corner.  
3. Use the ROCKER to point to the new location, and press  
ENTER.  
4. To stop the move process, press QUIT.  
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BASIC OPERATION > NAVIGATING TO A DESTINATION  
To activate a Go To from a point list:  
1. Press the NAV key. Highlight Go To Point, and press  
ENTER.  
Selecting a Go To Graphically  
A graphical Go To can be used to select one of three items from  
the map display: an existing waypoint, on-screen map items such  
as roads, rivers, cities, and navaids, or a new map point. If you are  
selecting a map item as the Go To destination, the GPSMAP 188/  
188C Sounder automatically uses the name of the map item, but  
the point is not stored in the waypoint list. See page 21 for creating  
waypoints using map items. If you are selecting a new map point  
(non-map item) as the Go To destination, the GPSMAP 188/188C  
Sounder automatically creates a waypoint at the pointer location.  
2. From the Find menu, highlight Waypoints or another menu  
option, and press ENTER.  
3. To select a waypoint from the waypoint lists, use the  
ROCKER to highlight either the By Name or Nearest tab,  
select a waypoint, and press ENTER.  
Or  
Select a waypoint from the map, highlight either the User or  
Nearest tab, and press MENU.  
With Select From Map highlighted, press ENTER. Use  
the zoom IN and OUT keys and the ROCKER to select a  
waypoint, then press ENTER.  
To activate an existing waypoint or map item as a Go  
To from the map display:  
1. Use the ROCKER to highlight the waypoint or on-screen  
map item, and press NAV. When Go To <waypoint name>  
appears, press ENTER.  
Or  
Highlight the waypoint or map item, and press ENTER.  
2. Highlight the Go To button at the bottom of the window, and  
press ENTER.  
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BASIC OPERATION > NAVIGATING TO A DESTINATION  
To Go To a new map point (non-map item):  
1. Use the ROCKER to move the map pointer to the location  
you want.  
TracBack Navigation (Navigating a Track)  
The TracBack function retraces your path using the track log  
automatically stored in the receiver’s memory. This feature  
eliminates the need to store waypoints along the way. TracBack  
routes are created by reducing your track log into a route of up to  
254 turns and activating an inverted route along those points. When  
activated, a TracBack route leads you back to the oldest stored  
track log point, so it is a good idea to clear the existing track log  
before you start your current trip.  
2. Press NAV.  
3. With Go To MAP Point highlighted, press ENTER.  
You must save a track before using the Follow Track option.  
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BASIC OPERATION > NAVIGATING TO A DESTINATION  
To view the track on the map, highlight Review on Map,  
and press ENTER. Pressing MENU to activate the Measure  
Distance (see page 32) and Point to on Main Map options,  
then exit the Save Track window. Press QUIT to return to  
the Save Track window.  
To clear the track log and define a starting point for a  
TracBack route:  
1. Press MENU twice to display the Main Menu.  
2. Using the ROCKER, highlight the Track tab, and highlight  
the Active sub tab.  
4. Highlight OK, and press ENTER to save the track.  
5. Press QUIT to exit.  
3. Use the ROCKER to select the Erase, and press ENTER.  
4. Highlight the OK, and press ENTER.  
You must save the track log before you can use Follow Track. The  
Save feature stores up to 15 track logs.  
Default Track Name  
To save a track log:  
1. From the Main Menu, use the ROCKER to highlight the  
Total number of points  
Total Distance  
Change color  
Track tab, and then highlight the Active sub tab to the right.  
of track line  
2. Use the ROCKER to select Save, and press ENTER.  
3. From the Save Back Through window, highlight time,  
Check this box to  
display track  
date, or Entire Log, and press ENTER When the track is  
.
saved, the Save Track window appears. The default name,  
distance, number of points (500 max), and color are in the  
Save Track window.  
To change the name of the saved track, highlight the name  
field, and press ENTER. Make your changes, and press  
ENTER.  
To display the track on the Map and Highway Pages,  
highlight the check box to the left of Show on Map and  
Highway, and press ENTER.  
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BASIC OPERATION > NAVIGATING TO A DESTINATION  
If the track log interval is set to the Time option, the route  
can not follow your exact path. For best performance, keep  
the interval set to resolution.  
To activate a TracBack using the NAV key:  
1. Press NAV, highlight the Follow Track, and press ENTER.  
2. Highlight the track you want to follow, and press ENTER.  
3. Choose Original to navigate from the start to the end of  
your trip, or choose Reverse to navigate from the end to the  
start of your trip, and press ENTER.  
If the receiver is turned off or satellite coverage is lost during  
your trip, the TracBack draws a straight line between any  
point where coverage was lost and where it resumed.  
4. To stop TracBack navigation, press NAV, highlight Stop  
Navigation, and press ENTER.  
If the track log’s changes in distance and direction are too  
complex, 254 waypoints can not mark your path accurately.  
The receiver then assigns the 254 waypoints to the most  
significant points of your track, and simplifies segments with  
fewer changes in direction.  
When a TracBack is active, the GPSMAP 188/188C Sounder  
takes the track log currently stored in memory and divides it into  
segments called legs. Up to 50 (188) or 254 (188C) temporary  
turns (BEGIN, TURN 1, TURN 2, TURN 3,...., TURN X, END)  
are created to mark the most significant features of the track log in  
order to duplicate your exact path as closely as possible. To get the  
most out of the TracBack feature, remember the following tips:  
For more information on setting up the Track options and saved  
tracks, see page 59.  
Always clear the track log at the starting point.  
Set the Record Mode option on the track log setup page to  
Fill or Wrap.  
The track log memory must contain at least two points to  
create a TracBack route.  
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BASIC OPERATION > ROUTES  
To create a route using the Route Edit Map Page:  
1. Press MENU twice to display the Main Menu.  
Routes  
You can create and store up to 50 user-defined reversible routes  
(numbered 1-50), with up to 254 waypoints each. Routes are  
created and modified in two ways. The first method creates the  
route using a map page. This method selects points on the map.  
The second method enters the waypoint names as text on the Route  
Review Page. This method lists the waypoints as you create the  
route. All of the route functions are accessed through the Main  
Menu or the NAV key.  
2. Use the ROCKER to highlight the Route tab, and press  
MENU to display the route options page, or highlight the  
first available blank route slot, and press ENTER. (Go to  
step 4 if you use this method.)  
3. Select New Route, and press ENTER.  
4. To add an existing waypoint or map item to the route, use  
the map pointer to select a waypoint or map item, and press  
ENTER. Map items do not appear in the waypoint list. To  
create a waypoint from a map item, see page 21.  
5. To add a new waypoint to the route, use the map pointer  
to select a map location, and press ENTER. Press ENTER  
again to confirm the new waypoint. You can also change the  
name and symbol of the new waypoint (see page 8).  
As you add each new waypoint to the route, the data  
window at the top of the map display shows the waypoint/  
map item name, bearing and distance from your location,  
and coordinates of the pointer. The bottom of the display  
shows the number of available and used points. A route line  
appears on the map to indicate each completed leg, and a  
dotted line appears indicating the distance and bearing to  
the arrow pointer from the last route waypoint.  
Route Tab  
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BASIC OPERATION > ROUTES  
6. Repeat steps 4 and 5 until you have finished defining all  
route waypoints.  
To create a route using text on the Route  
Review Page:  
1. Press MENU twice to display the Main Menu.  
7. When finished, press QUIT twice to return to the Route  
List. Highlight Edit as Text, and press ENTER to return to  
the Route Review Page.  
2. Use the ROCKER to highlight the Route tab, and press  
MENU to display the route options menu, or highlight the  
first available blank route slot, and press ENTER. (Go to  
step 4 if you use this method.)  
3. Select New Route, and press ENTER.  
4. Press MENU, select Edit as Text, and press ENTER.  
5. Use the ROCKER to highlight the first field under the word  
Waypoint, and press ENTER.  
ADD appears below the  
pointer as you insert points.  
Choose the category you want to  
add a route point from.  
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BASIC OPERATION > FIND  
6. From the Find menu, highlight Waypoints or another  
menu item, and press ENTER. From either the By Name  
or Nearest tab lists, choose a waypoint, and press ENTER.  
(See page 50 for searching for waypoints by name.)  
Find  
Use the FIND key to search the unit for user waypoints, map items  
and any BlueChart or MapSource information loaded to the unit  
or on a data card. Press FIND to display a list of available find  
categories. The default items are Waypoints, Cities, Tide Stations,  
and Transportation. If you press FIND and you are in Pan Mode,  
the unit centers its search from the map pointer location.  
7. On the Waypoint Review Page, OK is automatically  
highlighted. You can use Show Map to view a point on the  
map. When finished viewing, press QUIT to return to the  
Waypoint Review Page. Press ENTER to add the point to  
the route. The next field automatically highlights.  
8. Repeat steps 5-7 until all the route points are entered.  
Press QUIT to return to the Route List.  
Find Items List  
Choose a waypoint from either the  
By Name or Nearest tab list.  
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BASIC OPERATION > FIND  
The Find option also supports a “find from” feature that centers  
your search around an item you have just found. For example,  
you search for “Restricted Areas” and you find a point named  
“Anchoring Prohibited.” If you press FIND again, “From  
Anchoring Prohibited” appears as the new search from point.  
To Find an item from your current location:  
1. From any page, press FIND.  
2. Using the ROCKER, highlight a category from the list, and  
press ENTER.  
3. For Waypoints and Cities, search using By Name or  
Nearest. Use the ROCKER to highlight a tab. For By  
Name, use the top field to spell out the name, or scroll down  
through the list. (See page 8 for steps on entering a name.)  
You can also use the Find feature to center your search from any  
waypoint, route list entry, map item, or tide station. Highlight the  
item you want to find from, and press FIND.  
To Find an item from other locations:  
1. From the Map Page, use the ROCKER to pan to a location,  
and press FIND.  
Nearest To Boat—centers search from your boat’s current  
location.  
Nearest To Other—centers your search around another map  
location.  
2. Using the ROCKER, highlight a category from the list, and  
press ENTER.  
Nearest To Next—centers search from the next point of your  
active route.  
You can also Find  
from items found on  
the Find List.  
Nearest To Destination—centers search from the last point  
of your active route.  
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BASIC OPERATION > ADDITIONAL INFORMATION  
To Find an item using the Find options:  
From any page, press FIND.  
Additional Information  
1
Items located using the Find feature have information about the  
point available. The information varies depending on the type of  
data loaded on the optional data card. Sub tabs along the top of the  
detail window contain the information available for the item. Any  
additional options are displayed along the bottom.  
2. Using the ROCKER, highlight a category from the list, and  
press ENTER.  
3
From the search results list, press MENU, highlight an  
option, and press ENTER.  
To view additional information for a Find item:  
1. From the Find list, highlight an item, and press ENTER.  
2. Use the ROCKER to highlight the individual tabs and  
display the information. To scroll the text, highlight the field,  
and press ENTER. Use the ROCKER to scroll.  
Or  
Press MENU, and choose a scroll option.  
Additional  
Information Tabs  
Distance,  
Bearing,and  
Coordinates of item  
Find Menu Options  
Additional Options  
Information Window  
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BASIC OPERATION > DSC  
who they are and the type of vessel) in their database while they  
are in transit to the caller’s location.  
DSC  
The DSC tab on Main Menu controls and sets up the Digital  
Selective Calling (DSC) features on the GPSMAP 188/188C  
Sounder.  
A non-emergency DSC Position Report allows mariners to  
exchange and display the positions of one another. When a DSC  
position is received, the mariner can choose to create a waypoint or  
to show the received location on an electronic map.  
DSC uses marine VHF radio and Global Positioning System (GPS)  
technologies to transmit and receive location information. The  
chartplotter repeats the call properties received from the VHF radio  
on the chartplotter. The GPSMAP 188/188C Sounder requires input  
from a DSC enabled VHF radio to display position, and sound/  
display alerts from a Distress Call or Position Report. Conversely,  
the VHF radio requires input from a GPS to transmit position  
coordinates for a Distress Call or Position Report. For connection  
information, refer to “Connecting the Power/Data Cable” on  
page 98.  
Anytime a vessel receives a DSC call, they can store and quickly  
navigate to that location using a Go To. To use DSC, users must  
first register their VHF radios with the FCC and receive a Maritime  
Mobile Service Identity (MMSI) number. Garmin does not provide  
MMSI numbers.  
For more information about Digital Selective Calling and Maritime  
Mobile Service Identity (MMSI) numbers, refer to page 103 in the  
“Appendix.”  
An emergency DSC Distress Call allows a vessel in trouble  
to transmit a substantial amount of information in a single  
transmission or call, without the need for voice communication.  
When any nearby rescuers receives the DSC signal, an alarm  
sounds and they immediately receive the location of the caller.  
The rescuer can choose to navigate to the caller’s location to  
assist, or forward the call on to the Coast Guard. When the Coast  
Guard receives the call, they can immediately access the caller’s  
information (such as  
Understanding Distress Calls  
When the GPSMAP 188/188C Sounder receives a Distress Call  
from a connected DSC-enabled VHF radio, an alert message and  
notification page appear, and an alarm tone sounds. Distress Calls  
are shown in the DSC Call List and Log with a checkered symbol.  
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BASIC OPERATION > DSC  
When a Distress Call or Position Report is placed in the Call List  
and Log, the information on the Notification Page is retained.  
To review a DSC call or log entry, highlight the entry, and press  
ENTER. The DSC Entry Review window is identical to the  
Notification window with one exception, the entry can be deleted.  
Understanding Position Reports  
A Position Report is similar to a Distress Call except no alarm is  
sounded. Position Reports are not broadcast to all DSC users and  
are shown with a boat symbol.  
DSC Entry Review Window  
Receiving DSC Calls  
Each time you receive a Distress Call or Position Report, a  
Notification Page is appears, and the call is placed in the DSC Call  
List and Log. The Notification Page contains information about  
the call including the type of call (distress or position report),  
the MMSI number of the caller, a user definable name, the time  
and date of the call, the Bearing and Distance from your current  
position, and the coordinates of the caller. To see the caller’s  
location on a map, select the Show Map button. To create a  
waypoint at the caller’s location, select the Create Wpt button. To  
close the Notification Page, press QUIT.  
To review a call or log entry:  
1. Press Menu twice.  
2. Open the Call List or Log from the DSC tab.  
3. Press up or down on ROCKER to highlight the call you want  
to review.  
4. Press ENTER to open the DSC Entry Review window.  
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BASIC OPERATION > DSC  
3. Enter the MMSI number, a Name, and any comments.  
DSC Call List  
The DSC Call List displays the 50 most recent calls, even if the unit  
is left unattended. The Call List displays the most recent call from a  
vessel. If a second call from the same vessel is received, it replaces  
the first call in the Call List. Press MENU to sort the list and delete  
entries.  
4. When finished, highlight OK, and press ENTER.  
DSC Log  
When DSC calls are received, they are automatically placed in the  
Log, with the most recent call at the top. The unit can log up to 100  
calls. When 100 calls are logged, the oldest log is removed when a  
new call is received. Press MENU to sort the list and delete entries.  
New Directory Item Page  
DSC Directory  
When a Distress Call, Position Report, or Directory item is named,  
the name is attached to that particular MMSI number. If a name is  
used, all DSC entries of the same MMSI number show the name.  
The DSC Directory acts much like a phone book and can hold up  
to 50 entries. Pressing MENU from this page displays options to  
add a New Item, Delete a highlighted entry, or Delete All entries.  
To add a new Directory entry:  
1. Open the DSC Directory in the Main Menu.  
2. Use the ROCKER to highlight the first blank space in the  
directory list, and press ENTER.  
Or  
Press MENU, highlight New Item, and press ENTER.  
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BASIC OPERATION > DSC  
Navigating to a Position Report or Distress Call  
After a Position Report or a Distress Call is received, navigation  
can be quickly set to the call location.  
Setting up DSC  
The DSC Setup sub tab turns DSC chartplotter information display  
On and Off. This Setup tab also allows you to simulate Distress  
Calls and Position Reports while the unit is in Simulator Mode  
(see page 3). Simulating calls is helpful for practice before  
connecting to the real system. The Distress Call simulator also  
helps to check if alarms are working properly.  
To navigate to Position Report or Distress Call:  
1
Press NAV.  
2. With Go To MMSI/Name highlighted, press ENTER.  
Or  
1. Highlight the call on the Call List or Log, and press NAV.  
2. With Go To MMSI/Name or DSC highlighted, press ENTER.  
DSC Setup  
Navigating to a DSC Call  
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MAIN PAGES > OVERVIEW  
MAIN PAGES  
Six main display pages are always available: Map Page, Sonar Page, Pointer Page, Numbers Page, Highway Page, and Active Route Page.  
You can cycle through these pages by pressing either PAGE or QUIT. For information on the Sonar Page, refer to the “Using Sonar”  
section on pages 78-91.  
With the Map Page displayed, press PAGE several times. Each time you press PAGE the next main page appears. Do the same with the  
QUIT key. QUIT acts the same as PAGE, except the pages are displayed in a reverse sequence.  
Each main page has an options menu. Options menus contain the setup options and functions that apply to that page. Press MENU to  
display the options menu. Use the ROCKER to select an item from the options menu and press ENTER. Many of the menus in the  
GPSMAP 188/188C Sounder are arranged in a tab layout. Use the ROCKER to move left or right from tab to tab.  
Notice that either PAGE or QUIT stops the current function and returns you to the main page. If you find yourself lost in a menu or you  
start a function you do not want, press PAGE or QUIT.  
Pointer Page  
Numbers Page  
Map Page  
Sonar Page  
Highway Page Active Route Page  
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MAIN PAGES > MAP PAGE  
Data Fields  
Map Page  
The Map Page provides a comprehensive display of electronic  
cartography, plotting, and navigational data. When in the BlueChart  
data coverage area or using optional MapSource software, the  
map display shows your boat on a digital chart, complete with  
geographic names, map items, navaids, and a host of other chart  
features. It also plots your track and displays any routes and  
waypoints you create. A map pointer allows you pan and scroll to  
other map areas, determine the distance and bearing to a location,  
and perform various route and waypoint functions.  
Land  
User Waypoint  
Map Item  
Water  
Position Triangle  
Navaids  
Geographic  
Name  
Map Range  
When the map pointer is active, an additional data window appears  
below the data fields to indicate the location, range, and bearing  
to the pointer, a selected waypoint, or map item. The map range  
displays at the bottom right of the page.  
Map Page shown using  
optional MapSource data.  
The GPSMAP 188/188C Sounder system starts in the Position  
Mode, with your location centered on the map display. When  
sufficient map coverage is not available to keep your location  
centered, the position triangle moves toward the edge of the  
display.  
The Zoom IN and OUT keys combined with the ROCKER, allow  
you select zoom ranges and move the pointer. Two basic map  
operating modes, Position Mode and Pointer Mode, determine what  
cartography is shown on the map display. Position Mode moves the  
cartography to keep the present location marker within the display  
area. Pan Mode moves the cartography to keep the map pointer  
within the display area.  
Pan Mode starts when the ROCKER is pressed. The pointer  
is moved over the map display using the ROCKER. When the  
pointer reaches the edge of the display, the map scrolls forward  
under the pointer.  
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MAIN PAGES > MAP PAGE  
Using the Map Pointer  
Additional  
The pointer pans away from your present location (even outside  
of your current detail coverage.) As you pan past the edge of the  
current map display, the screen actively scrolls forward to provide  
continuous map coverage. An hourglass symbol appears by the  
pointer while the unit is busy drawing new map details.  
Information Tabs  
Pressing ENTER while  
highlighting a map item  
brings up additional  
details and options.  
Additional Options  
To select an on-screen waypoint or map item with the  
map pointer:  
1. Use the ROCKER to move the map pointer to a waypoint or  
map item. (If there are several waypoints grouped closely  
together, zoom in closer for a better view.)  
Move the pointer  
over an item  
on the map to  
highlight it.  
2. When a waypoint or map item is selected, it is highlighted  
on-screen, with the name and location displayed. Press  
ENTER to show details of the map item. When in the  
BlueChart coverage area or using optional MapSource  
data, additional information tabs appear. Use the ROCKER  
to highlight the individual tabs, and display additional  
information and options.  
As you move the pointer, the distance and bearing from your  
present location to the pointer is displayed in the data window,  
along with the pointer’s location coordinates. Keep in mind that  
when the pointer is stationary, the distance and bearing from your  
present position changes as your location moves. The pointer can  
also be used to view on-screen waypoint and map item properties  
directly from the map display.  
3. Press QUIT to re-center your location on-screen.  
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MAIN PAGES > MAP PAGE  
Use the pointer to create new waypoints directly from the map.  
Selecting Map Ranges  
The map display has 28 available zoom ranges from 20 ft to 800 mi  
(5 m to 1200 km.) The map range is controlled by the IN and OUT  
keys, with the current range displayed at the bottom right of the  
data window.  
To create a waypoint with the pointer:  
1. Use the ROCKER to move the pointer to the map location.  
2. Press ENTER. The New Map Waypoint window appears.  
(If the pointer is on a map item, press ENTER, and a new  
window with details about the item appears.)  
To select a map range:  
3. Press ENTER again on the highlighted Create Wpt option.  
Press the OUT key to zoom out and the IN key to zoom in.  
4. Press ENTER to confirm the new waypoint using the default  
NOTE: The range value represents the distance from one end  
of the range bar to the other.  
three-digit name and symbol.  
For more information about waypoints, see page 8.  
Using Built-In Basemap  
Using BlueChart/MapSource Data  
Overzoom, no additional data is available  
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MAIN PAGES > MAP PAGE  
The GPSMAP 188/188C Sounder’s system has a built-in  
worldwide database to 20 mi, with more detailed coverage  
available through the use of the optional BlueChart or MapSource  
data. The GPSMAP 188/188C Sounder displays cartography as  
long as there is chart information available for the range you have  
selected. Map coverage conforms to the following conditions:  
Map Page Options  
Many features of the GPSMAP 188/188C Sounder are menu  
driven. Each main page has an options menu, allowing you to  
customize the corresponding page to your preferences and select  
special features that specifically relate to that page. The data  
window, located at the top of the main pages, provides a user-  
selectable layout of various types of useful data. Each data field can  
be configured to display any one of several data options. The data  
window layout can be configured to display additional data fields  
and change the size of the data displayed.  
When the selected zoom range is covered by the internal  
database, BlueChart, or MapSource data, cartography is  
displayed.  
When the selected zoom range is covered by both  
the internal database and BlueChart/MapSource data,  
cartography is displayed using the data with the best  
resolution.  
To display and select the Map Page options:  
1. Press MENU.  
2. Use the ROCKER to highlight an option, and press ENTER.  
When the selected zoom range exceeds the resolution of the  
data in use, an Overzoom warning appears below the range.  
The available options are Full Screen Map/Show Data, Change  
Numbers, Measure Distance, Show Sonar (If equipped with a  
transducer, see the “Using Sonar” section on pages 78-91 for  
details on this feature,) Set Up Map and Turn Declutter On/Off.  
Following are details on using each of these options.  
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MAIN PAGES > MAP PAGE  
Change Numbers—specifies the type of data displayed in each  
data field used on the map display.  
To change a data field:  
1. From the menu, use the ROCKER to highlight the Change  
Numbers option, and press ENTER.  
2. Move the field highlight to the data field you want to change,  
and press ENTER.  
3. Move up or down on the list using the ROCKER to highlight  
the data you want to display, and press ENTER. To exit,  
press QUIT.  
Map Page Options  
Full Screen Map/Show Data—toggles between the Map Page  
without or with data fields on the map display.  
To maximize the map/show data fields:  
1. Highlight Full Screen Map, and press ENTER. The Map  
Page is now maximized with no data fields.  
2. To show the data fields again, press MENU, highlight Show  
Data, and press ENTER.  
NOTE: Pointer, Highway, Location, and Sonar field options  
are only available on medium and large sized data fields.  
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MAIN PAGES > MAP PAGE  
3. Move the pointer to the end measurement point. The  
bearing and distance from the reference point and pointer  
coordinates appears in the data window at the top of the  
display. Press QUIT to finish.  
You can also merge the four medium default data fields to a single,  
large field for better readability or you can split any or all of the  
default data fields to show four small data fields.  
Single, large data  
field  
Pointer  
Coordinates  
Default, medium  
fields  
Distance and  
Bearing  
Split, small  
fields  
Map Pointer  
Measure Distance—measures the bearing and distance between  
any two points on the map display.  
Full screen map shown  
(with BlueChart data)  
To measure the bearing/distance between two points:  
1. Highlight Measure Distance, and press ENTER. An  
on-screen pointer labeled ENT REF appears on the map  
display at your present location.  
2. Move the pointer to a reference point (the point that you  
want to measure from), and press ENTER.  
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MAIN PAGES > POINTER PAGE  
Set Up Map—configures the map display preferences, including  
map detail, map orientation, automatic zoom, and various map  
items and points. Refer to “Main Menu—Map Tab” on page 64 for  
more information.  
Pointer Page  
The Pointer Page provides graphic steering guidance to a  
destination waypoint, with an emphasis on the bearing to your  
destination and current direction of travel. The middle of the  
page features a rotating compass ring that shows your course  
over ground (track) while you are moving, and a bearing pointer  
that indicates the direction of the destination (bearing) relative  
to the course over ground. The compass ring and pointer arrow  
work independently to show—at a glance—the direction of your  
movement and the direction to your destination. For instance, if  
the arrow points up, you are going directly to the waypoint. If the  
arrow points any direction other than up, turn toward the arrow  
until it points up—then continue in that direction.  
To change a map setup feature:  
1. From the Map Page menu, highlight Set Up Map, and press  
ENTER.  
2. Press left or right on the ROCKER to highlight a tab, then  
press up or down on the ROCKER to highlight the setting  
you want to change, and press ENTER.  
3. Press up or down on the ROCKER to highlight to a setting,  
and press ENTER. To exit, press QUIT.  
From the map setup page, you can access the following menu  
The current speed, distance to the next waypoint, turn angle and  
current location are displayed at the top of the screen. This page  
provides better steering guidance when traveling at slower speeds  
or when making frequent directional changes. When you are not  
navigating to a waypoint, the compass ring shows the current  
direction of travel but the arrow does not appear.  
options by pressing MENU.  
Defaults—restores settings back to factory settings for the  
tab highlighted.  
All Map Defaults—restores settings back to factory settings  
for all tabs.  
Turn Declutter On/Off—toggles between showing BlueChart spot  
soundings and map outlines for easier viewing.  
NOTE: The bearing pointer, bearing bug, and compass ring  
can point in various directions when you are stationary or at  
very low speeds. Once you start moving, the pointer is correct.  
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MAIN PAGES > NUMBERS PAGE  
Numbers Page  
The Numbers Page provides for precision navigation to one degree  
of steerage. The default page displays three large numbers fields.  
You can customize the Numbers Page to display the size and  
number of fields along with the type data you want to see. See  
page 31 for instructions on changing the data fields.  
Current  
Go To  
Destination  
Data  
Fields  
Bearing  
Bug  
The Numbers Page provides a quick reference for the important  
data you want to display. By default, the page displays three large,  
user-selectable data fields showing a compass ribbon, speed, and  
current location coordinates. You can also choose to show the three  
data fields in large lettering for better readability or you can split  
any or all of the data fields to show four smaller data fields. See  
page 31 for detailed instructions on changing the data fields and  
layout of the Numbers Page.  
Compass  
Ring  
Bearing  
Pointer  
The Pointer Page features a menu page that provides access to  
layout and data field options. The data window, located at the top  
of the page, provides a user-selectable layout of various types of  
useful data. Each data field can be configured to display several  
data options. The data window layout can be configured to display  
additional data fields and change the size of the data displayed.  
To display and select the Pointer Page options:  
1. Press MENU.  
2. Use the ROCKER to highlight an option, and press ENTER.  
For detailed instructions on changing the data fields and  
layout of the Pointer Page, see page 31.  
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MAIN PAGES > HIGHWAY PAGE  
Highway Page  
The Highway Page provides graphic steering guidance to a  
destination waypoint, placing greater emphasis on the straight-line  
course, and the distance and direction you are off course. As you  
head toward your destination, the middle of the screen provides  
visual guidance to your waypoint on a moving graphic highway.  
Your present location is at the bottom center of the highway  
display. The line down the middle of the highway represents your  
course. As you navigate toward a waypoint, the highway moves—  
indicating the direction you are off course. To stay on course, steer  
toward the center of the highway.  
Numbers Page  
shown with middle  
data field split into  
four fields  
To split the data fields:  
1. Press MENU, and press ENTER.  
2. Highlight a data field, and press MENU.  
3. Highlight Split Numbers, and press ENTER. Four new data  
fields appear. Press QUIT to finish.  
Steer toward  
the center of the  
highway or toward  
the black vertical  
bar on the compass  
ribbon to get back  
on course.  
4. To return to the original configuration, repeat steps  
1 and 2, but instead of Split Numbers, select either Merge  
Numbers or Defaults. Press QUIT to finish.  
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MAIN PAGES > HIGHWAY PAGE  
The four data fields at the top of the page provide additional  
user-selectable guidance information. Additionally, a compass  
ribbon shows your current heading along with a dark vertical bar  
that indicates the direct bearing to the navigation point. When the  
dark, vertical indicator (or arrow) lines up with the lighter red bar  
in the middle, you are heading directly to the navigation point.  
Use the Highway Page as your primary navigation page in lieu of  
the Pointer Page when your main concern is following a defined  
course.  
You can zoom in or out on the Highway display for a smaller or  
larger view. Five available settings range from 1X to 16X, with a  
default setting of 8X. The current range appears in the bottom right  
of the display.  
To zoom in or out on the highway display:  
Press either the IN or OUT key to increase or decrease the  
zoom range.  
Highway Page Options  
The Highway options page defines the data fields and selects the  
waypoints and tracks that are displayed. The data window, located  
at the top of the page, provides a user-selectable layout of various  
types of data. Each data field can be configured to display several  
data options. The data window layout can be configured to display  
additional data fields and change the size of the data displayed.  
Current  
Waypoint  
Data Fields  
Course  
To display and select the Highway Page options:  
1. Press MENU.  
2. Using the ROCKER, highlight an option, and press ENTER.  
Present  
Location  
Zoom  
Range  
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MAIN PAGES > ACTIVE ROUTE PAGE  
Active Route Page  
Check or uncheck  
the options you  
want to show/hide  
on the Highway  
Page.  
The Active Route Page shows each point of the active route, with  
the point name, distance and choice of Course, ETA, Fuel, Leg  
Distance, Leg Fuel, Leg Time, Sunrise, Sunset, or Time To for each  
point from your present location. The current destination point is  
marked with an arrow icon. As you navigate a route, the waypoint  
list automatically updates to indicate the next active point first. The  
Active Route and Route Review Pages share many of the same  
features and options. For more information on the Active Route  
Page, see page 17.  
Preview Window  
NOTE: The Active Route Page only appears when the unit is  
navigating to a destination using a route, TracBack, or Go To.  
Highway Page Set Up  
The following options are available from the Highway Page menu:  
Set Up Highway—selects what waypoints and tracks are shown  
on the Highway display. Use the ROCKER and ENTER keys to  
select or deselect the options.  
Change Numbers—specifies the type of data displayed in each  
data field used. For detailed instructions on changing the data fields  
and layout of the Highway Page, see page 31.  
Active Route Page  
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MAIN PAGES > ACTIVE ROUTE PAGE  
Re-evaluate—reactivates the current route and selects the route  
leg closest to your current location as the active leg. The active leg  
defines the current from and to waypoints.  
Active Route Page Options  
The following options are available from the Active Route Page:  
Hide/Show Numbers—see page 31 for instructions (same  
as Map Page option).  
To re-evaluate an active route:  
1. From the Active Route Page, press MENU.  
Change Numbers—see page 31 for instructions.  
Edit on Map—see page 17 for instructions.  
Add Before—see page 17 for instructions.  
Remove—see page 17 for instructions.  
2. Using the ROCKER, highlight Re-evaluate and press  
ENTER to recalculate.  
Invert—reverses the direction of the route.  
Re-evaluate—recalculates and reactivates the current route.  
Invert—reverses the route.  
To invert an active route:  
1. From the Active Route Page, press MENU.  
2. Using the ROCKER, highlight Invert, and press ENTER to  
reverse the route.  
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MAIN MENU > GPS TAB  
To select a Menu tab from the Main Menu Page:  
MAIN MENU  
1. Press up or down on the ROCKER to highlight a tab. The  
information for the highlighted tab automatically appears  
to the right. If you want to select any of the sub tab items,  
press right on the ROCKER, and press up or down to select  
individual items.  
The Main Menu provides access to various waypoint, system,  
navigation, interface management, and setup menus. The 19 Menu  
tabs are divided into categories by function. The Main Menu is  
available from any page in the system, and is accessed by pressing  
MENU twice. See page 6 for additional instructions on changing  
settings and entering data.  
2. Either press MENU for additional submenu options, or press  
ENTER to make changes to the highlighted item. Press left  
on the ROCKER to get back to the Main Menu tabs list.  
Sub Tabs  
3. Press QUIT to return to the Main Menu.  
GPS Tab  
The GPS tab provides a visual reference of satellite acquisition,  
receiver status, and accuracy. The status information provides  
an idea of what the receiver is doing at any given moment. The  
sky view and signal strength bars give you an indication of what  
satellites are visible to the receiver and whether or not they are  
being tracked. The signal strength is shown on a bar graph for each  
satellite, with the satellite number below. As the receiver locks onto  
satellites, a signal strength bar appears for each satellite in view.  
Main Menu  
Tabs  
Main Menu  
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MAIN MENU > GPS TAB  
The progress of satellite acquisition is shown in three stages:  
You can use the sky view to help determine if any satellites  
are being blocked, and whether you have a current location fix  
(indicated by a 2D, 2D Differential, 3D, or 3D Differential in  
the status field). The sky view shows a bird’s-eye view of the  
position of each satellite relative to the receiver’s last known  
location. The outer circle represents the horizon (north up), the  
inner circle 45º above the horizon, and the center point a position  
directly overhead. You can also set the sky view to a Track Up  
configuration, causing the top of the sky view to align along your  
current track heading.  
No signal strength bars—the receiver is looking for the  
satellites indicated.  
Light signal strength bars—the receiver has found the  
satellite(s) and is collecting data.  
Dark signal strength bars—the receiver has collected the  
necessary data and the satellite(s) are ready for use.  
Receiver  
Status  
Accuracy  
WAAS Capability  
DOP  
The GPSMAP 188/188C Sounder is capable of receiving WAAS  
(Wide Area Augmentation System) satellite signals. WAAS is an  
FAA (Federal Aviation Administration) funded project to improve  
the overall accuracy and integrity of the GPS signal for aviation  
use, but land/sea based users can also benefit from this system. At  
this time, the system is still in the development stage and is not  
fully operational.  
Differential  
Sky View  
Status  
Signal Strength  
Bars  
There are currently two WAAS satellites that can be received in the  
U.S.A., one over the Atlantic Ocean and one over the Pacific  
The status field indicates a 2D or 3D, when the GPSMAP  
188/188C Sounder has collected the necessary data from satellites  
to calculate a fix. The unit then updates the location, date, and time.  
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MAIN MENU > GPS TAB  
Ocean, in a geo-stationary orbit over the equator. Effective use  
of the WAAS satellite signal can be limited by your geographic  
location in relation to those satellites, now in developmental  
service. WAAS satellite signal reception requires an absolute  
clear view of the sky and works best when there are no nearby  
obstructions such as buildings or mountains.  
To Disable/Enable WAAS capability:  
1. From the GPS tab, press MENU.  
2. Use the ROCKER to highlight WAAS Off or WAAS On, and  
press ENTER.  
WAAS satellites are numbered 33 or higher when viewing the sky  
view on your GPSMAP 188/188C Sounder. Initial reception of  
the WAAS signal can take up to 15-20 minutes, then 1-2 minutes  
afterward. When WAAS differential correction has been received  
for GPS satellites (numbers 32 or below), a D appears in the  
signal bar of the sky view and 2D or 3D Differential appears in the  
receiver status. To learn more about the WAAS system, its satellite  
positions and current state of development, visit the FAA web site  
(http://gps.faa.gov). Because WAAS requires CPU resources of the  
GPSMAP 188/188C Sounder to search for and track the satellites,  
you can disable the WAAS feature to improve unit performance  
if WAAS reception is not available in your area. Refer to the  
“Appendix” for more information.  
Highlight WAAS Off, and press ENTER  
to disable the WAAS capabilities.  
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MAIN MENU > GPS TAB  
AutoLocate—the receiver is looking for any satellite whose  
The Differential Receiver status shows one of the following:  
almanac has been collected. This process can take up to five  
minutes.  
Off—No optional beacon receiver attached or enabled in the  
Comm menu or WAAS Off.  
Acquiring Satellites—the receiver is looking for and  
collecting data from satellites visible at its last known or  
initialized position, but has not collected enough data to  
calculate a fix.  
Searching For WAASWAAS is enabled and receiver is  
searching for WAAS signal.  
Using WAASWAAS capability enabled and unit receiving  
WAAS corrections.  
2D—at least three satellites with good geometry have been  
acquired and a 2 dimensional position fix (latitude and  
longitude) is being calculated. “2D Differential” appears  
when you are receiving DGPS corrections in 2D mode and a  
D shows on the strength bar of satellites being corrected.  
No Beacon Signal—DGPS receiver attached, but not  
transmitting RTCM data to GPS.  
Tuning Beacon—receiver is tuning manual DGPS  
frequency.  
Receiving Beacon—unit is receiving DGPS corrections.  
3D—at least four satellites with good geometry have been  
acquired and your location is now being calculated in  
latitude, longitude and elevation. “3D Differential” appears  
when you are receiving DGPS corrections in 3D mode and a  
D shows on the strength bar of satellites being corrected.  
Scanning Beacon—DGPS receiver is scanning for available  
frequency.  
The Differential SNR (Signal to Noise Ratio) indicates, on a range  
to 0-30db with 30db being the best, the strength of the DGPS signal  
being received. The SNR depends on the mounting of your DGPS  
receiver and the distance from the DGPS transmitting station. If  
no optional DGPS receiver is used with the GPSMAP 188/188C  
Sounder, the DGPS Rcvr field displays Off.  
Poor GPS Coverage—the receiver is no longer tracking  
enough satellites for a 2D or 3D fix.  
Receiver Not Usable—the receiver is unusable, possibly  
due to interference or abnormal satellite conditions. Turn the  
unit off and back on to reset.  
Simulating—the receiver is in Simulator Mode.  
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MAIN MENU > TIDE TAB  
GPS Tab Options  
The GPS tab features an options page that provides access to  
functions and features relating to the GPS Info display.  
Tide Tab  
The Tide tab shows a graphical chart that displays tide station  
information in a 24 hour span starting at midnight station time. You  
can choose from different dates and more than 3,000 tide stations.  
To display and select the GPS Tab options:  
1. Press MENU.  
Station  
Name  
2. Using the ROCKER, highlight an option, and press ENTER.  
NOTE: If a DGPS receiver is attached to the unit and Garmin  
DGPS, RTCM In/NMEA Out, or Other DGPS is enabled on  
Port 2, WAAS is automatically disabled (WAAS Off). It is not  
possible for the GPSMAP 188/188C Sounder to receive WAAS  
and DGPS corrections at the same time.  
Date  
Tide  
Chart  
Event  
Times  
Tide Tab  
The top of the page displays the tide station being referenced,  
below that the date. The top of the chart shows a 24-hour block of  
local time (LCL) for your location, with the reported station time  
(STA) appearing at the bottom. Daytime (light bar) and nighttime  
(dark bar) show across the time scale, with the time progressing  
from left to right. (Local time scales and sunrise/sunset info cannot  
be available for a few stations). The solid, light vertical lines are  
GPS Tab Options  
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MAIN MENU > TIDE TAB  
in 4-hour increments, and the light, dotted vertical lines are in  
1-hour increments. A solid vertical line (with the current time box  
at the top) indicates the time of day when using current date and  
intersects the tide graph to show their relationship.  
The tide curve shows as a shaded area, where higher tides are taller  
(blue) and lower tides are shorter (red). The solid, horizontal line  
(with the current tide box on the left) indicates the current tide  
height. The figure to the left of the line shows the current tide level  
in feet. The Mean Lower Low Water (MLLW) appears as a solid,  
horizontal line near the bottom of the chart (This line only appears  
if the tide ranges to the zero value or below). The numbers directly  
below/above LCL and STA indicate the maximum/minimum levels,  
respectively. The four data fields below the chart, indicate event  
times and levels the tide changes starting in the upper left field,  
going downward, then to the upper right and down again.  
You can select from  
a list of nearest  
stations.  
To select the nearest tide station from you current  
location:  
1. From the Tide tab, highlight the At field, and press ENTER.  
Local Time  
Max. Level  
Day  
2. Highlight a tide station on the list, and press ENTER twice.  
Current Time Bar  
High Tide  
Curve  
Current Tide  
Height Bar  
Low Tide  
Curve  
MLLW  
Night  
Min. Level  
Station Time  
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MAIN MENU > TIDE TAB  
You can automatically search for the nearest station using a variety  
of search locations. You must select a location within 100 nm of  
a tide station. If you are not within this range, you see a message  
“None Found.” Use the Nearest To Other Find option and select a  
location closer to a tide station.  
To select a tide station from the map:  
1. When the search results appear, press FIND, and highlight  
Tide Stations.  
2. Press ENTER, and then press MENU.  
3. Highlight Nearest To Other, and press ENTER.  
4. Select a location on the map, and press ENTER. A list  
appears showing the nearest tide stations.  
5. Highlight a station, and press ENTER twice. If the None  
Found message appears, repeat steps 1-4 until you find a  
station.  
To change the date for the tide chart:  
1. Using the ROCKER, highlight the On field, and press  
ENTER.  
2. Enter the date, and press ENTER.  
To use the current date:  
Press MENU, highlight Use Today’s Date, and press  
ENTER.  
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MAIN MENU > TRIP TAB  
Move the time bar on the tide chart in 5 minute increments to show  
tide heights at various times on the chart.  
Trip Tab  
The Trip tab displays the Trip Odometer, Moving Average speed,  
Total Average speed, Maximum Speed, Stopped Time, Moving  
Time, Total Time, and Odometer. To reset the data, choose from  
Reset Trip, Reset Max Speed, Reset Odometer, or Reset All, and  
press ENTER.  
To see tide heights at various times on the chart:  
1. Press MENU, highlight Move Cursor, and press ENTER.  
2. Press left or right on the ROCKER to change the time.  
Press QUIT when finished or press MENU, highlight Stop  
Moving Cursor, and press ENTER.  
Move the pointer to  
see tide heights at  
different times. Tide  
data shows in a black  
box when in pointer  
mode.  
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MAIN MENU > CELES TAB  
To choose a position:  
1. From the Celes tab, highlight the At field, and press  
Celes (Celestial) Tab  
The Celestial tab displays celestial data for sun and moon rise/set,  
moon phase, and approximate sky view location of the sun and  
moon. The moon phase displays the current visible portion of the  
moon as a light color. You can display this data for your current  
location, a location from the map, or a Find item location. Use the  
current data, or select a different date and time.  
ENTER.  
2. From the Find list highlight any category except Other  
Location, and press ENTER. If you want to reference a  
Find item, select from the Find list, and press ENTER.  
3. Select an item from the list or tab lists, and press ENTER.  
4. For a location from the map, choose Other Location, press  
ENTER, select a location on the map, and press ENTER.  
5. From the Find item detail page, highlight OK, and press  
ENTER.  
Position  
Date/Time  
The location the unit is using appears in the Date/Time/Position  
field. The time tables displayed are based on your current time  
zone. When using a position from another location outside of your  
time zone, you need to set the Time Zone for that location. See  
page 62 for more information on setting time zones.  
Sky View  
Window  
Sun/Moon  
Event Times  
Moon Phase  
Sun Position  
Moon  
Position  
Overhead (90°)  
Horizon (0°)  
70° 45°  
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MAIN MENU > POINTS TAB  
Points Tab  
The Main Menu Points tab features two waypoint sub tabs, User  
and Proximity, that manage a large number of waypoints quickly  
and efficiently. The sub tabs also provide a continuously updated  
proximity waypoint alarm function that can be used to define an  
alarm circle around items such as submerged hazards or shallow  
waters.  
Sub Tabs  
Celestial Tab Menu  
To change the time or date:  
1. From the Celes tab, use the ROCKER to highlight the date  
Main Menu  
Tabs  
or time, and press ENTER.  
2. Enter a new date or time, and press ENTER.  
To use current date and time:  
From the Celes tab, press MENU, use the ROCKER to  
highlight Use Current Date and Time, and press ENTER.  
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MAIN MENU > POINTS TAB  
The following options are available from the User submenu of the  
Points tab:  
To select the Points (Waypoint) sub tab:  
1. Use the ROCKER to highlight the Points tab. A list of stored  
waypoints appear to the right of the Main Menu list.  
Create Waypoint—allows you to create a waypoint. (See  
page 8 for information on creating a waypoint)  
2. Press right one time on the ROCKER. The User tab is now  
highlighted.  
Delete Waypoint—deletes the selected waypoint from the  
waypoint list and route.  
3. Press down on the ROCKER until a waypoint is highlighted.  
User Waypoint List  
Delete By Symbol—deletes waypoints that uses the same  
symbol.  
The first waypoint submenu list available from the Points tab is the  
User list, which displays a master list of all waypoints currently  
stored in memory. From the User list, you can review, edit, rename  
or delete individual waypoints, or delete all user waypoints. The  
total number of stored and available waypoints is displayed at the  
bottom of the User page, with the stored waypoints arranged in  
numerical/alphabetical order.  
Delete All—deletes all waypoints from the unit.  
NOTE: When a waypoint is deleted from the list, it cannot be  
recovered from the unit. It is advisable to backup important  
waypoints to a computer using an optional PC cable and  
interface software or record them manually.  
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MAIN MENU > POINTS TAB  
To display the waypoint menu options:  
Using the ROCKER, highlight the User tab, and press  
MENU.  
To delete an individual waypoint from the list:  
1. Use the ROCKER to highlight the waypoint to delete, and  
press MENU.  
2. Highlight Delete Waypoint, and press ENTER. You can  
also highlight the waypoint, press ENTER, highlight Delete,  
and press ENTER.  
To scroll through and review the waypoint list:  
1. With the ROCKER, highlight the Points tab from the  
Main Menu, and then highlight User.  
3. Select OK, and press ENTER to confirm the deletion  
2. Use the ROCKER to scroll through the list.  
warning.  
3. Press ENTER to review the highlighted waypoint on the  
Waypoint Edit Page.  
4. Press ENTER to return to the list and automatically highlight  
the next waypoint.  
To search for a waypoint by name:  
1. Highlight the name field, and press ENTER.  
2. Use the ROCKER to select the first letter of the name.  
3. Move to the right, and enter the second letter, if you do not  
see the name in the list below.  
4. Repeat this until the name appears. Press ENTER when  
you see the name.  
5. Highlight the name on the list, and press ENTER again  
to review the waypoint. When finished, highlight OK, and  
press ENTER.  
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MAIN MENU > POINTS TAB  
To delete waypoints by symbol:  
1. From the User sub tab, highlight the waypoint to delete, and  
Proximity Waypoint List  
The Proximity list allows you to define an alarm circle around a  
stored waypoint location, and can be used to help you avoid reefs,  
rocks, or restricted waters. Up to 10 waypoints can be listed, with  
a maximum alarm radius of 99.99 nautical or statute miles or  
kilometers. If a proximity alarm circle overlaps with an existing  
alarm circle, a “Proximity Overlaps Another Proximity Waypoint”  
message appears. Because the unit only alerts for one of the  
overlap points, use caution when navigating in these areas. If you  
enter an alarm circle overlap, you are only alerted to the closest  
proximity waypoint.  
press MENU. Select Delete By Symbol, and press ENTER.  
2. Use the ROCKER to highlight the symbol of the waypoint(s)  
to delete, and press ENTER.  
3. Press ENTER to confirm. To stop the deletion, choose  
Cancel, or press QUIT.  
To delete all waypoints or the entire waypoint list:  
1. Press MENU to select the options window.  
2. Use the ROCKER to highlight Delete All, and press  
ENTER.  
3. Highlight OK, and press ENTER to confirm.  
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MAIN MENU > POINTS TAB  
To add a proximity waypoint:  
To turn on or off proximity alarms:  
1. Use the ROCKER to highlight the field below Proximity  
Alarm, and press ENTER.  
1. Use the ROCKER to highlight an empty space on the  
Proximity list, and press ENTER. The Find screen appears.  
Highlight Waypoints, and press ENTER.  
2. Select a ON or OFF setting, and press ENTER.  
2. To select a waypoint from the list, use the ROCKER to  
highlight a waypoint from the User or Nearest tab.  
Or  
To display the waypoint menu options:  
Using the ROCKER, highlight the Proximity tab, and press  
MENU.  
To select a waypoint from the map, highlight either the User  
or Nearest tab, and press MENU. With Select From Map  
highlighted, press ENTER. Use the zoom In and Out keys  
and the ROCKER to highlight a waypoint.  
To clear one or all proximity waypoint(s) from the list:  
1. Use the ROCKER to highlight the proximity waypoint, and  
press MENU.  
3. Press ENTER to confirm. The distance field is now  
2. To clear a single alarm, highlight Delete Alarm, and press  
ENTER.  
highlighted.  
4. Press ENTER to begin entry of the proximity radius.  
3. To clear all proximity waypoints, select the Delete All  
option, and press ENTER.  
5. Use the ROCKER to enter a distance value (to 99.99 units)  
and press ENTER.  
4. Use the ROCKER to highlight OK, and press ENTER.  
The following options are available from the Proximity sub tab of  
the Points tab:  
Proximity Waypoint  
Proximity Circle  
Delete Alarm—removes a selected waypoint from  
proximity list.  
A dashed circle  
appears showing  
the alert boundary  
for the proximity  
waypoints.  
Delete All—removes all waypoints from proximity list.  
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MAIN MENU > ROUTES TAB  
Routes Tab  
The Route List Page displays all the routes currently stored in  
memory, along with a descriptive name for each route. After a route  
has been created, it can be activated and used for navigation with  
the NAV key. A route can be followed in the same sequence as it  
was originally created, or you can invert the route and navigate  
from the end waypoint back to the beginning waypoint. From  
the Route list menu, you can choose New Route (page 17), Copy  
Route, Delete Route, or Delete All.  
If you highlight a route  
name from the Route  
List and press NAV,  
the name automatically  
appears.  
To stop navigation of a route:  
To start a route with the NAV key:  
Press NAV, highlight Stop Navigation, and press ENTER.  
1. From any page, press NAV, highlight Follow Route, and  
press ENTER. If you highlight a route from the Route  
List or Route Review Page, and press NAV the window  
automatically displays Follow <the route name>.  
To copy or delete a route:  
1. From the Route List, highlight the route you want to copy or  
delete using the ROCKER, and press MENU.  
2. Highlight the route you want to navigate, and press ENTER.  
2. Choose either Copy Route or Delete Route and press  
ENTER. With OK highlighted, press ENTER again to  
confirm a deletion. Copy uses the same route name with  
an additional number, starting at 1, at the end of the route  
name.  
3. Choose Activate or Invert and Activate, and press  
ENTER. Activate uses the route as is. Invert and Activate  
reverses the route, then starts.  
To delete all routes:  
1. From the Route List, press MENU.  
2. Highlight Delete All, and press ENTER. With OK  
highlighted, press ENTER again to confirm the deletion.  
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MAIN MENU > ROUTES TAB  
Route Review Page  
After you create a route, use the Route Review Page to review and  
modify the route displayed.  
Route Name  
Data Fields  
Route Points  
Data Totals  
To show the Route Review Page:  
1. Press MENU twice, and highlight the Route tab.  
2. Highlight the route you want to review, and press ENTER.  
The Route Review Page also allows you to enter your own 15-  
character name for any listed route. By default, the name includes  
the first and last waypoints in the route.  
To enter a custom route name:  
1. From the Route Review Page, highlight the name field, and  
press ENTER to begin editing.  
2. Use the ROCKER to enter a name, and press ENTER.  
Route List Menu  
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MAIN MENU > ROUTES TAB  
When you are on the Route Review Page, you can review the route  
points (waypoints or map items) one at a time from the list.  
Route Review Menu Options  
Menu options available from the Route Review Page are Edit on  
Map, Add Before, Remove, and Trip Planning.  
To review individual route points:  
1. Highlight a point, and press ENTER.  
2. On the waypoint review window, you can choose Next  
(highlight the next point on the route list), Show Map (show  
the point on a map window), or Delete (permanently delete  
the waypoint from the unit), and press ENTER.  
When you are back on the route point list, the next point in the  
route is automatically highlighted. This allows you to review each  
point on the route by pressing ENTER repeatedly.  
Highlight a point, and press ENTER to review it.  
Route Review Options Menu  
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MAIN MENU > ROUTES TAB  
Edit on Map—allows you to review and modify the route  
displayed for each point (waypoint or map item) on a map page.  
Use the pointer to insert a new route point on a route leg, review  
the waypoint, or map item.  
To add turns at the beginning or end of the route:  
1. Select the first (to add waypoints to the beginning of the  
route) or last (to add waypoints to the end of the route)  
route waypoint with the map pointer, and press MENU.  
2. Highlight the Add option and press ENTER.  
To edit the route on the map:  
3. Move the pointer to the new point or location, and press  
From the Route Review Page, press MENU, highlight  
Edit on Map, and press ENTER.  
ENTER.  
4. If you are not inserting an existing waypoint, press ENTER  
To edit a route point:  
to confirm the new waypoint.  
Use the ROCKER to highlight a route waypoint, and press  
MENU.  
5. Repeat steps 3 and 4 to insert additional waypoints, or  
press QUIT to finish.  
To review a route point:  
The route edit mode also allows you to insert a new route waypoint  
in any route leg using the map pointer.  
Highlight the point, and press ENTER. Press ENTER again  
when finished.  
To insert a new waypoint between two existing route  
waypoints:  
1. Use the ROCKER to select the leg you want to insert the  
new waypoint in (the route line is now highlighted and a  
dotted line appears when the leg is selected), and press  
ENTER.  
A pop-up menu of editing choices appear, with options for  
removing, moving (user waypoints only), or adding turns to the  
beginning or end of the route.  
To remove a route waypoint:  
Highlight the Remove option, and press ENTER.  
2. Move the pointer to the new map location, existing  
waypoint, or map item (ADD is displayed below the arrow  
and the route lines move with the arrow), and press ENTER.  
To move a route waypoint:  
1. Highlight the Move option, and press ENTER.  
2. Move the pointer to the new map location, and press  
3. If you are not inserting an existing point, press ENTER to  
ENTER.  
confirm the new waypoint.  
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MAIN MENU > ROUTES TAB  
Add Before—inserts a waypoint into the list of route points or add  
a point(s) onto the end of the route.  
Drag the route  
leg to an existing  
waypoint (shown),  
map item, or a  
blank spot on the  
map to create a  
new route point.  
To insert a point into the route, or add a point to  
the end of the route:  
1. From either the Route Review or Active Route Pages, use  
the ROCKER to highlight the point you want to insert the  
new point before (to add a point to the end, highlight the  
blank field at the bottom of the list), and press MENU.  
2. Highlight Add Before, and press ENTER.  
Remove—removes a point (waypoint or map item) from a route.  
This option is available from both the Route Review and Active  
Route Pages.  
3. From the Find menu, highlight Waypoints, and press  
ENTER. (You can also choose from other points, such as  
Cities or Tide Stations from this list.) From either the User  
or Nearest From Current Location tab lists, choose the  
waypoint you want and press ENTER twice. (See page 50  
for information on searching for waypoints by name.)  
Or  
To remove a point from a route:  
1. From either the Route Review or Active Route Pages,  
use the ROCKER to highlight the point to remove, and  
press MENU.  
To select a waypoint from the map, highlight the User or  
Nearest tab and press MENU. With Select From Map  
highlighted, press ENTER. Use the zoom IN and OUT keys,  
and the ROCKER to highlight a waypoint on the map, and  
press ENTER.  
2. Highlight Remove, and press ENTER.  
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MAIN MENU > ROUTES TAB  
Trip Planning—the Route Review and Active Route Pages also  
display trip-planning information for each leg or the entire route.  
Available information includes Course, ETA, Fuel (to point),  
Leg Distance, Leg Fuel, Leg Time, Sunrise and Sunset (at point  
location), and Time To (point).  
Trip  
Planning  
Data Fields  
To use the Trip Planning feature:  
1. To select a planning field, highlight a route from the Route  
List, and press ENTER to display the Route Review Page.  
One of nine available planning fields appears to the right of  
each route waypoint and its distance.  
NOTE: Fuel flow rates on your unit are measured in units  
per hour. System setting changes for units of measure (statute,  
nautical or metric) do not affect the fuel flow measure. You  
should enter fuel flow rates based on available information  
for your vehicles (operators manual, or performance  
specifications.) Make note of the units of measure  
(gallons or liters.)  
2. Press left or right on the ROCKER to select an item.  
3. To enter planning information, from the Route Review  
Page only, press MENU, and select Trip Planning from  
the options list. Enter the figures for Speed, Fuel Flow,  
Departure Time, and Departure Date. Press QUIT to return  
to the Route Plan Page.  
Delete Route—deletes a route from the Route List. Waypoints and  
map items are not deleted from the unit’s memory.  
To delete a route:  
1. From the Route Review Page, press MENU.  
2. Highlight Delete Route and press ENTER.  
3. Press ENTER again to confirm the deletion.  
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MAIN MENU > TRACK TAB  
Saved Sub Tab  
Track Tab  
The Saved sub tab displays and manages a list of any saved track  
logs, allows for TracBack activation, and map display of saved  
logs. The active log stores up to approximately 2,500 track log  
points, based on the criteria specified in the Track settings. Up to  
15 track logs can be saved in memory, with up to 500 track log  
points in each saved log. A TracBack can be activated from any of  
the saved tracks on this tab.  
The Track tab specifies whether or not to record a track log, define  
how it is recorded, or save track log data for future use. The Track  
Logs page also provides an indicator of the memory used for the  
active track log and options to clear the track memory or start a  
TracBack route. See page 14 for TracBack information. The Track  
submenu is divided in two sub tabs: Active and Saved.  
Active Sub Tab  
The Active sub tab is for the active log (the log currently being  
recorded). It displays track memory used and current settings.  
Saved Sub Tab  
Active Sub Tab  
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MAIN MENU > TRACK TAB  
For the Active sub tab, the following settings are available:  
Record Mode—contains three track recording options:  
Value—defines the distance or time used to record the track  
log.  
Save—saves the current active track log.  
Off—the track log is not recorded. Selecting the off setting  
Erase—clears the active track log stored in memory.  
prevents you from using the TracBack feature.  
For the Saved sub tab, the following menu options are available:  
Fill—a track log is recorded until the track memory is full.  
Review On Map—displays the saved track log on a Track  
Map Page.  
Wrap—records the track log continuously. After the  
available memory is full, the oldest track data is replaced  
with the newest track data.  
Delete Track—deletes the highlighted saved track log from  
memory.  
Interval—defines the frequency the track plots are recorded. Three  
interval settings are available:  
Delete All—deletes all saved track logs from memory.  
Distance—records track based on a user-defined distance  
between points.  
Time—records track plot based on a user-defined time  
interval.  
Resolution—records track plot based on a user-defined  
variance from your course over ground. The resolution  
option is the default setting and is recommended for the most  
efficient use of memory and TracBack performance. The  
distance value (entered in the value field) is the maximum  
error allowed from the true course before recording a track  
point.  
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MAIN MENU > DSC TAB  
You can use the Review On Map option to display a saved track on  
a Track Map page.  
DSC Tab  
Digital Selective Calling (DSC) uses marine VHF radio and Global  
Positioning System (GPS) technologies to transmit and receive  
location information. DSC is used by mariners to assist them in two  
major areas: Distress Calls and Position Reporting. See page 22  
and the “Appendix” for more information on DSC and using it with  
your GPSMAP 188/188C Sounder.  
To activate a TracBack from the Saved tab list:  
1. Using the ROCKER, highlight a track, and press NAV. The  
Follow <track name> automatically appears highlighted.  
2. Press ENTER.  
3. Choose either Original, which navigates you from the end  
to the start of your trip, or Reverse, which navigates you  
from the start to the end of your trip, and press ENTER.  
The track name  
automatically  
appears when  
highlighted on the  
Saved list and  
NAV is pressed.  
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MAIN MENU > CARD AND TIME TABS  
Card Tab  
Time Tab  
The Card tab contains options for saving waypoints, routes and  
tracks to a data card. When data is saved to a data card, it can be  
exchanged with other compatible units and Garmin’s MapSource  
PC program.  
The time tab displays the current time and date, allows you to  
adjust the 12 or 24 hour time format, enter a time zone, and adjust  
for daylight saving time.  
The following options are available:  
To transfer data to/from a data card:  
1. Insert the data card. From the Card tab, select the check  
Time Format—choose from 12 or 24 hour (military) time  
format.  
box next to each type of item you want to transfer.  
Time Zone—choose your correct time zone to show correct  
local time or enter a UTC Offset. The UTC (also called  
Greenwich Time) offset is how many hours you are ahead or  
behind the time line.  
2. Highlight Save To Card, and press ENTER to save the  
selected items to the data card.  
3. If transferring data from the card to the unit, highlight Merge  
From Card, and press ENTER to combine the selected  
items with those of your GPS.  
Daylight Savings Time—choose from Auto, On, or Off to  
adjust for daylight saving time.  
4. Highlight Replace From Card, and press ENTER to  
overwrite all selected items on your GPS. A Transfer  
Complete message appears after the data is transferred.  
5. Press QUIT to exit.  
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MAIN MENU > PAGES TAB  
You can also press MENU, choose from one of the following, and  
press ENTER:  
Pages Tab  
The Pages tab allows you to turn on or off any of the main pages or  
Jump To a particular page. You can also set the page that appears  
first when you turn on the unit or enable/disable the GPS Info on  
the initial screen.  
All Pages—selects all pages.  
Chartplotter Only—selects the Map Page only.  
Nav Tools Only—selects the Pointer, Numbers, Highway,  
To select or deselect a main page:  
1. Use the ROCKER to highlight the box to the left of the  
page name.  
and Active Route Pages only.  
Basic Fishfinder—selects the Sonar Page only if equipped  
with a transducer.  
2. Press ENTER to select or deselect that page. When a page  
is selected a check mark appears in the box. You must  
leave at least one page selected.  
Defaults—selects all pages.  
First Page  
Option  
To set the first page:  
1. Use the ROCKER to highlight the First page option, and  
press ENTER.  
2. Highlight the page you want to appear first, and press  
ENTER.  
Pages Tab  
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MAIN MENU > MAP TAB  
AutoZoom—On, Off: when On the map automatically  
adjusts the map range to a lower range as you approach your  
destination point.  
Map Tab  
The Map tab changes the display properties of the Map Page.  
The following pages contain descriptions of the Map tab’s eight  
sub tabs.  
Color Mode—Water Mode, Land Mode: lightens the shade  
of the water areas in Water Mode and land in Land Mode.  
This option is only available on the GPSMAP 188.  
General Sub Tab  
Source Sub Tab  
Detail—Most, More, Normal, Less, Least: controls how  
much map detail appears. This setting only applies to map  
features set to Auto. Features that have a specified zoom  
range or are turned off are unaffected by this setting.  
Basemap—On/Off: turns the built-in basemap on or off.  
Data Card Maps—On/Off: turns on or off all BlueChart or  
MapSource data loaded in the unit or on the data card.  
Orientation—North Up: fixes the top of the map display to  
a north heading. Track Up: fixes the top of the map display  
to the current track heading. Course Up: fixes the map so the  
direction of navigation is always up.  
Built-in Maps—On/Off: turns on or off all built-in  
BlueChart maps.  
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MAIN MENU > MAP TAB  
To display the Map Information Page:  
1. Highlight the Data Card Maps button, and press ENTER.  
Waypoints Sub Tab  
2. Use the ROCKER to scroll through the list of maps.  
3. To select or deselect a map, highlight the check box to the  
left of the name of a map and press ENTER. The map is  
selected and is appears on the Map Page when a check  
mark appears in the box adjacent to that map.  
The Waypoints and Active Route options each contain adjustments  
for text and zoom.  
4. To display detailed information and notes for each area,  
highlight a name, and press ENTER.  
Text—None, Small, Medium, and Large: controls the screen  
size of the name.  
5. To view the notes for that area, choose Show Notes. To  
scroll through the notes, highlight the notes, press ENTER,  
and use the ROCKER to scroll up, down, left, and right, or  
press MENU and choose a scroll option.  
Zoom—Auto, Off, 120 ft-800 mi: sets the maximum zoom  
range features should appear on the Map Page. Some types  
of data only are visible at specific zoom ranges.  
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MAIN MENU > MAP TAB  
Points Sub Tab  
Navaids Sub Tab  
Symbol Set—Auto, Garmin, NOAA, International: controls  
a navaid symbol set.  
The Spot Soundings, Tide Stations, and Services options each  
contain adjustments for text and zoom.  
Text Size—Small, Medium, and Large: controls the screen  
size of the name.  
Text—None (except Spot Soundings), Small, Medium, and  
Large: controls the screen size of the name.  
Light Sectors—Off, Auto, On: controls the drawing light  
sectors on the map.  
Zoom—Auto, Off, 120 ft-800 mi: sets the maximum range  
features should appear on the Map Page. Some types of data  
only are visible to specific zoom ranges.  
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MAIN MENU > MAP TAB  
Nav Line Sub Tab  
Other Sub Tab  
Heading Line—On/Off: draws an extension from the end of  
the boat icon in the direction of travel.  
Accuracy Circle—On/Off: toggles the circle On and Off.  
The circle represents the approximate accuracy of the unit  
based on EPE, DOP, and basemap quality. Your location is  
within the circle.  
Bearing Line—On/Off: toggles the black/white line that  
points to the current navigation point.  
Lat/Lon Grid—Text—None, Small, Medium, and Large:  
controls the screen size of the name. Zoom—Auto, Off, 120  
ft-800 mi: sets the maximum range the feature should appear.  
Course Line—Auto, Off, 120 ft-800 mi: sets the maximum  
zoom range that the course line appears on the screen.  
Track Sub Tab  
Map Outlines—On/Off: toggles the coverage boxes for  
BlueChart/MapSource data on and off.  
The Saved Tracks and Track Log options each contain adjustments  
for zoom.  
Zoom—Auto, Off, 120 ft-800 mi: sets the maximum range  
the feature should appear on the Map Page. Some types of  
data only are visible to specific zoom ranges.  
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MAIN MENU > HIWAY, TEMP, AND SONAR TABS  
Hiway (Highway) Tab  
Sonar Tab  
The Highway tab contains display settings for the Highway Page.  
Refer to the “Highway Page” section on page 35.  
The Sonar tab contains setup options for the Sonar Page. The Sonar  
Page is not active if you do not have a transducer connected. Refer  
to the “Using Sonar” section on pages 78-91 for more information  
on sonar setup options.  
Temp (Temperature) Tab  
The Temperature tab displays the water temperature log. The  
temperature log requires input from a temperature transducer/  
sensor. The most recent temperature measured displays on the far  
right side of the chart with the history trailing to the left. The dotted  
lines within the chart indicate intervals in the temperature range  
and the duration of time.  
The following settings are available:  
Temperature Scale—controls the temperature range for  
displaying the log. Select Auto to have the unit automatically  
determine the best range, or select a span of 2, 4, 6, 8, or 10  
degrees.  
Time Duration—controls the number of temperature  
readings displayed on the log. Shorter time durations display  
a greater the number of log points. Use longer time durations  
to detect temperature trends, instead of immediate readings.  
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MAIN MENU > SYSTM TAB  
The following option is also available from the Systm tab:  
Systm (System) Tab  
The System tab controls system setting for beeper, speed filter,  
languages, system mode, and simulator controls, restores factory  
settings, displays the software version, and prepares software  
update cards.  
System Information—displays the unit’s software, basemap  
version, and electronic serial number.  
Press MENU to access the following options:  
Defaults—restores settings on Systm page to default values.  
The following settings are available:  
All Unit Defaults—restores all settings to Garmin’s original  
setup values for the entire unit.  
Beeper—Off, Alarms Only, Key and Alarm: controls audible  
beeps for keys and alarms.  
Speed Filter—Off, Auto, On: averages speed-readings.  
Language—displays the on-screen display languages.  
System Mode—sets Normal or Simulator Mode.  
Set Position*—sets your location while in Simulator Mode.  
See page 3 for additional instructions.  
Track Control*—Auto Track, User Track: controls your  
heading in Simulator Mode.  
Track*—sets your heading in Simulator Mode.  
Speed*—sets your speed in Simulator Mode.  
Transducer*—sets a transducer type.  
* These fields are only available when the unit is in Simulator Mode.  
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MAIN MENU > UNITS TAB  
Map Datum—sets the datum reference used to determine  
a given location. The default setting is WGS 84. The  
unit automatically chooses the best datum depending on  
your chosen position format. Datums are used to describe  
geographic locations for surveying, mapping, and navigation.  
You should only change the datum if you are using a map or  
chart that specifies a different datum.  
Units Tab  
The Unit tab defines the Position Format, Map Datum, Heading,  
Distance, Speed, Elevation, Depth, and Temperature units.  
The following settings are available:  
Position Format—changes the coordinate system. You  
should only change the position format if you are using a  
map or chart that specifies a different position format or want  
to use a format with which you are familiar.  
WARNING: Selecting the wrong map datum can result in  
substantial position errors. Unless otherwise specified by  
the navigation documentation you are using, use the default  
WGS 84 datum for best overall performance.  
For additional information on Loran TD setup, see page 108.  
NOTE: The Units tab settings affects how navigation  
information is displayed on the GPSMAP 188/188C Sounder.  
When in doubt, seek assistance.  
If you are using a map or chart in conjunction with your GPS,  
make sure the settings under the Units tab of the GPSMAP 188/  
188C Sounder match that of the map or chart. This information  
should be displayed somewhere on the map or chart. If the  
information is not present, contact the map or chart maker to  
determine what position format, datum, heading and units of  
measure are being used for the map or chart.  
Units Tab  
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MAIN MENU > UNITS TAB  
Heading—selects the reference used in calculating heading  
information. You can select from Auto Mag Var, True, Grid,  
and User Mag Var. Auto Mag Var provides magnetic north  
heading references that are automatically determined from  
your current location. True provides headings based on a  
true north reference. Grid provides headings based on a grid  
north reference (and is used in conjunction with the grid  
position formats described on page 70). User Mag Var allows  
you to specify the magnetic variation at your current location  
and provides magnetic north heading references based upon  
the variation you enter.  
Manually enter a  
magnetic variation.  
Distance, Speed and Elevation—allows you to select the  
units of measure for distance, speed, and elevation readouts  
in nautical (nm, kt, m), statute (mi, mh, ft), or metric  
(km, kh, m) terms.  
To enter a user defined magnetic variation:  
1. With the Heading field set to User Mag Var, highlight the  
heading reference field (immediately to the right), and press  
ENTER.  
Depth—allows you to select the units of measure for depth  
in feet (ft), fathoms (fa) or meters (m).  
2. Use the ROCKER to enter the magnetic variation at your  
current location and press ENTER.  
Temperature—allows you to select the units of measure for  
temperature in Fahrenheit (°F) or Celsius (°C).  
WARNING: If User Mag Var is selected, you must periodically  
update the magnetic variation as your location changes. Using  
this setting, the unit does not automatically calculate and  
update the magnetic variation at your present location. Failure  
to update this setting can result in substantial differences  
between the information displayed on your unit and external  
references, such as a magnetic compass.  
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MAIN MENU > COMM TAB  
Port 2  
Comm (Communications) Tab  
The Communications tab controls the input/output format used  
when connecting your GPSMAP 188/188C Sounder to external  
NMEA devices, a DGPS beacon receiver, a personal computer, or  
another Garmin unit.  
Garmin DGPS—supports connections with a Garmin DGPS  
beacon receiver.  
Other DGPS—supports DGPS input using a standard  
RTCM format, without any output capabilities.  
NMEA In/NMEA Out—supports the input/output of  
standard NMEA 0183 data, and sonar NMEA support for the  
DBT, DPT, MTW, and VHW sentences. You can also adjust  
the NMEA output.  
NOTE: If a DGPS receiver is used, WAAS capability is  
automatically turned to off. See pages 98 and 99 for wiring and  
NMEA version information.  
The unit supports two input/output ports.  
RTCM In/NMEA Out—supports Differential GPS (DGPS)  
input using a standard RTCM format and also provides  
NMEA 0183 output.  
Port 1  
Garmin Data Transfer—the proprietary format used to  
upload/download MapSource data, exchange waypoint,  
route, track, almanac, and proximity data with a PC or  
another Garmin unit. When you select Garmin Data  
Transfer, there are 11 Transfer Modes to choose from:  
Host, Request Almanac, Request Proximity, Request Routes,  
Request Tracks, Request Waypoints, Send Almanac, Send  
Proximity, Send Routes, Send Tracks, and Send Waypoints.  
None—provides no interfacing capabilities.  
NOTE: The GPSMAP 188/188C can only send DBT and DPT  
NMEA sentences. It cannot input DBT and DPT sentences.  
NMEA In/NMEA Out—supports the input/output of  
standard NMEA 0183 data, and sonar NMEA input support  
for the DPT, MTW, and VHW sentences.  
None—provides no interfacing capabilities.  
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MAIN MENU > COMM TAB  
To select a transfer mode:  
1. Use the ROCKER to select Garmin Data Transfer in the  
Serial Data Format field.  
2. Highlight the Transfer Mode field, and press ENTER.  
3. Use the ROCKER to select a setting, and press ENTER.  
Advanced NMEA settings to adjust the NMEA output are available  
if you have one of the ports set to NMEA In/NMEA. Advanced  
NMEA settings enable/disable certain sentences and adjust the  
number of Lat/Lon output precision digits. Settings affect both Port  
1 and Port 2 NMEA outputs.  
When transferring data between two Garmin  
units, always set one to Host and use the other  
unit to either Send or Request the data.  
To select an input/output format:  
1. Select Port 1 or Port 2, highlight the Serial Data Format  
field, and press ENTER.  
2. Use the ROCKER to select a setting, and press ENTER.  
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MAIN MENU > COMM TAB  
To adjust the NMEA output:  
1. From the Comm tab, press MENU, highlight NMEA Setup,  
To restore the Serial Data Format settings back to the  
default Garmin Data Transfer:  
and press ENTER.  
From the Comm tab, press MENU, highlight Defaults, and  
press ENTER.  
2. Highlight an option, and press ENTER.  
If Garmin DGPS or RTCM In/NMEA Out format is selected,  
additional fields are provided to control a Garmin differential  
beacon receiver directly from your GPSMAP 188/188C Sounder.  
The unit can automatically scan for the DGPS beacon signal, or  
you can enter the beacon frequency and bit rate on the unit and the  
information is used to tune the beacon receiver.  
3. Use the ROCKER to select a setting, and press ENTER.  
Press QUIT to return to the Comm tab.  
To have the unit automatically scan for a frequency:  
1. With the unit set to Garmin DGPS or RTCM In/NMEA Out,  
use the ROCKER to highlight the Beacon field, and press  
ENTER.  
2. Highlight Scan, and press ENTER. The numbers in the  
Frequency field change as the unit scans from 284 kHz to  
325 kHz, 200 bit rate, then 100 at 6-second intervals.  
Advanced NMEA Output  
Setup Page  
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MAIN MENU > COMM TAB  
To manually enter a frequency and bit rate:  
1. With the unit set to Garmin DGPS or RTCM In/NMEA Out,  
use the ROCKER to highlight the Beacon field, and press  
ENTER.  
Status Field  
2. Highlight User, and press ENTER.  
3. Highlight the Frequency or Bit Rate field, press ENTER,  
enter a frequency or bit rate, and press ENTER when  
finished.  
SNR and  
Distance shows  
data when signal  
The Status field shows one of the following:  
Tuning—the unit is attempting to tune to the specified  
frequency and bit rate.  
NOTE: The DGPS beacon transmitters are operated by  
the U.S. Coast Guard (or similar government agency in  
other countries), and are responsible for their accuracy and  
maintenance. For DGPS transmitter problems or to find the  
most updated list of frequencies and coverage areas, contact  
your local USCG, or see their Web site at  
Scanning—the unit is automatically scanning through the  
frequencies and bit rates.  
Receiving—the unit is receiving DGPS signal and ready for  
operation.  
Check Wiring—the unit is not making connection with  
http://www.uscg.mil/.  
DGPS receiver.  
To restart the scan:  
When the unit is receiving a DGPS signal, the SNR (Signal to  
Noise Ratio) and distance fields show data. The SNR range is  
0dB to 30dB, with 30 being the best. The Distance can or can not  
show data, depending on the signal being broadcast from the  
DGPS site.  
Press MENU, highlight Restart Scan, and press ENTER.  
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MAIN MENU > ALARM TAB  
Arrival—sets an alarm to sound when at specified distance  
or time away from a destination waypoint. Enter a distance  
radius or time for sounding the alarm and use the control  
field to set the alarm to Off, Dist (Distance), or Time.  
Alarm Tab  
The Alarm tab allows you to define the alarm settings. The Alarm  
tab is divided into three sub tabs: System alarms, Nav alarms, and  
Sonar alarms.  
Off Course—sets an alarm to sound when you are off  
the course by a specified distance. Enter a distance in the  
distance field and use the control field to turn the off course  
alarm on and off.  
System Sub Tab  
Clock—provides an alarm for the system clock. Enter a  
time in the time field, and turn the alarm on and off from  
the control field menu. Remember to enter alarm times in  
the same time format (UTC or local) you are using for your  
system. The unit must be on for the clock alarm to work.  
Sonar Sub Tab  
You must be receiving sonar NMEA data for these functions to  
work. See “Using Sonar” pages 78-91 for more information.  
Battery—sets an alarm to sound when the battery is  
reaching a critical state of discharge.  
Shallow Water/Deep Water—set alarms to sound when  
you enter an area of specified depth that is too shallow or too  
deep. Enter a depth in the distance fields and use the control  
fields to turn the alarms on and off.  
DGPS and Accuracy—DGPS alarm sounds when the unit  
loses a differential fix. The accuracy alarm sounds when the  
GPS position accuracy falls outside the user-set value.  
Water Temperature—sets an alarm to sound when the  
transducer reports a temperature either above, below, inside,  
or outside the specified values.  
Nav Sub Tab  
Anchor Drag—sets an alarm to sound when you have  
exceeded a specified drift distance. Enter a value in the  
distance field, and use the control field to turn the alarm on  
and off.  
Fish—sets alarm to sound when unit detects a fish of the  
specified symbol size.  
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MAIN MENU > ALARM TAB  
To set an alarm:  
1. Use the ROCKER to highlight a sub tab.  
2. Highlight the field you want to set, and press ENTER.  
3. Enter a setting, and press ENTER.  
If Persist is checked,  
an alarm stays active  
until acknowledged.  
4. If you want the alarm to display and beep until  
acknowledged, highlight the Persist box, and press  
ENTER.  
Press ENTER to  
acknowledge an  
alarm.  
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USING SONAR > SONAR PAGE  
Sonar Page  
USING SONAR  
The Sonar Page is where your GPSMAP 188/188C Sounder  
becomes a powerful fishfinder/flasher. To view the Sonar Page,  
press PAGE or QUIT repeatedly until it appears. Fish are  
displayed as colored arches or as fish icons. Both fish icons and  
arches are displayed in three different sizes. Thermoclines are  
shown as shades of blue. The area of strongest sonar return is  
displayed as solid white (if Whiteline is active. Typically, the  
bottom is the primary whiteline. A thin whiteline indicates a soft  
bottom and a thick whiteline follows the contour of the bottom  
and show any objects of reasonable size. For more information on  
understanding sonar and the display, see page 89.  
This section covers the additional sonar options for the GPSMAP  
188/188C Sounder when used in conjunction with a transducer.  
Read the Transducers Installation Instructions to properly install  
the transducer.  
NOTE: You MUST have a transducer installed and connected  
to your GPSMAP 188/188C Sounder to use the sonar features.  
Adjustment  
Menu  
Sonar Page  
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USING SONAR > SONAR PAGE  
2. Press up or down on the ROCKER to select the option, and  
press ENTER to access the adjustment window.  
Using the Adjustment Menu  
The Adjustment menu gives you direct access to the settings and  
features most commonly used on the Sonar Page. The option  
selected currently appears in the upper left of the display.  
3. To exit any of the adjustment options, press QUIT.  
To change an Adjustment menu setting:  
1. Select an adjustment option to change using one of the  
two methods described previously. The adjustment window  
automatically times out and disappears when the unit is idle  
for 20 seconds.  
Press MENU and  
highlight  
Adjustments to see  
a list of all options  
and their current  
settings.  
2. Press the ROCKER up or down to place the pointer  
or setting bar at the setting, range, or percentage  
(Off, 1-100%).  
3. Press ENTER or QUIT to exit the adjustment window,  
or press left or right on the ROCKER to view another  
adjustment window.  
To select an adjustment option from the Sonar Page:  
1. Press the ROCKER left/right to scroll through the options in  
the upper left of the display.  
To change a setting back to Normal or Auto:  
1. While on the adjustment window for the option, press  
MENU.  
2. Press ENTER to access the option’s adjustment window.  
2. Select the setting, and press ENTER.  
Or  
1. Press MENU, highlight Adjustments and press ENTER. A  
list of all options and their current settings appears, with the  
selected option highlighted.  
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USING SONAR > SONAR PAGE  
Zoom Adjustment  
Range Adjustment  
4X Split Zoom Display (Dual Frequency Mode)  
Range—sets the display depth range used for viewing. The unit  
can be set to automatically track the bottom or set to a user-  
specified depth range. Auto Mode displays the most information  
possible while continuously showing the bottom.  
2X Split—shows two reduced-size sonar pictures at the  
same time. The right half of the display screen shows the  
complete sonar picture at its original scale. The left half  
shows a portion of the original picture at 1/2 depth scale.  
Zoom—used to quickly select a display zoom range or split  
the display. When a range other than No Zoom is selected, the  
Adjustment Menu displays a new selection labeled View. The  
Zoom setting is divided into six display levels:  
2X Zoom—displays the 2X zoomed picture on the full  
screen and does not show the original depth scale.  
4X Split—shows two reduced pictures; the right at the  
original depth scale and the left at 1/4 the original depth  
scale.  
4X Zoom—displays only the 4X zoomed picture on the full  
screen. However, if Dual Frequency Display is set to Split,  
then a 50/200kHz split screen appears.  
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USING SONAR > SONAR PAGE  
Btm (Bottom) Split—shows two reduced pictures; the right  
at the original depth scale and the left showing sonar returns  
from the bottom up. All target depths read as a distance from  
the bottom.  
Gain—allows you to control the sensitivity  
of the unit’s receiver. This provides some  
flexibility in what is seen on the display.  
To see more detail, increase the receiver  
sensitivity by selecting a higher gain  
percentage. If there is too much detail  
or if the screen is cluttered, lowering the  
sensitivity can increase the clarity of the  
display.  
Btm (Bottom) Lock—displays only the Bottom Lock  
picture (returns from the bottom up) on the full screen.  
However, if Dual Frequency Display is set to Split, then a  
50/200kHz split screen appears.  
Gain Adjustment  
When activated, the zoomed picture becomes the Sonar Page  
display. You can also cycle through the sonar zoom display levels  
by pressing the IN or OUT keys. The Zoom function can be turned  
off by pressing the OUT key until the No Zoom setting appears.  
Target Level—adjusts how dark or  
light a return (or target) is displayed  
on-screen. A Color Bar (see page 86)  
appears on the right side of the screen  
as you adjust this setting. The higher  
the percentage, the darker the return  
appears. This setting does not increase  
or decrease the unit gain.  
View/Span—available when a Zoom scale  
other than No Zoom is selected. The View or  
Span setting is used to change the viewing  
range of a zoomed display. If the Zoom is  
set to 2X split or 4X split, only the zoomed  
portion on the left side of the screen is  
Target Level Selection  
affected by the change. If the Zoom is set to  
Bottom Split or Bottom Lock, Span adjusts  
how far off the bottom the unit displays  
View Adjustment  
data. In Zoom mode, you can control the  
view of the left side of the split.  
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USING SONAR > SONAR PAGE  
Whiteline—controls how the unit displays  
Depth Line—adds a horizontal depth line across  
the display that is used to measure the depth of  
underwater objects. The depth of the line appears  
in a box on the right side of the line. Press up or  
down on the ROCKER to control the position of  
the line on the graph. The depth is displayed in a  
window on the right side of the line. To turn the  
Depth Line Off, press the ROCKER up until the  
setting bar is all the way at the top of the range  
and reads Off.  
information about the bottom type (hard or soft).  
With the Whiteline Off, the bottom return displays  
as red and contains no information on bottom  
hardness. With Whiteline set at Normal or 1-100%,  
the bottom return becomes white with a red line  
indicating where the water meets the bottom. To  
turn the Whiteline Off, press the ROCKER down  
until the setting bar is all the way at the bottom  
of the range and reads Off. See page 91 for more  
detail on this feature.  
Depth Line  
Adjustment  
Whiteline  
Adjustment  
Noise Reject—helps filter unwanted noise from  
the graph. The Noise Reject tool can be turned Off,  
set to Normal (automatically adjusts for optimum  
viewing), or to a fixed 1-100% setting. When  
setting the Noise Reject tool, the HIGHER the  
noise rejection setting, the less likely the unit is  
to NOT show fish or structures. To turn the Noise  
Reject Off, press the ROCKER down until the  
setting bar is all the way at the bottom of the range  
and reads Off.  
Frequency—allows you to choose a transducer  
frequency. Frequency refers to the pitch of the  
sound that the transducer sends and receives. You  
can choose 200kHz, 50kHz, or Dual frequency.  
Frequency  
Adjustment  
Noise Reject  
Adjustment  
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USING SONAR > SONAR PAGE  
Scroll—adjusts the rate that the graph scrolls from  
right to left. If you are sitting still or the graph is  
moving too fast, slowing the scroll rate or pausing  
it can be beneficial.  
To display the Sonar Page options:  
Press MENU.  
To select a menu option:  
Use the ROCKER to highlight the option, and press  
ENTER.  
The following option is available:  
Adjustments—lists the Adjustment Menu options and their current  
settings (see page 79).  
Scroll  
Adjustment  
To change an Adjustment setting:  
1. While on the Adjustment options list, use the ROCKER to  
Sonar Page Options  
highlight the option, and press ENTER.  
The GPSMAP 188/188C Sounder’s Sonar Page features a menu  
page that provides access to additional functions and to layout and  
data field options.  
2. Use the ROCKER to make the change, and press ENTER.  
Show/Hide Pointer—allows you to reference sonar items and  
mark underwater waypoints. This makes it easier to find and use  
an object such as a stump for a future fishing location. When using  
this feature, the Sonar Page pauses. The pointer does not move off  
the paused display and cannot show an area that has scrolled off  
the screen. The depth is updated while the display is paused, but  
the unit does not show any new sonar data until the standard Sonar  
Page is resumed. You can see a discontinuity from where the sonar  
information stops to where it starts again.  
Sonar Page Menu Options  
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USING SONAR > SONAR PAGE  
4. To change the name, symbol or depth, highlight the  
appropriate field and press ENTER. Make your changes  
and press ENTER when finished.  
Data Window  
5. When finished, highlight OK, and press ENTER.  
6. To return to the standard Sonar Page, press QUIT; or press  
MENU, highlight Hide Pointer, and press ENTER.  
Pointer  
Show/Hide Numbers—toggles showing/hiding the data fields on  
the sonar display.  
Show Pointer Option  
To mark an underwater waypoint:  
1. From the Sonar Page, press MENU, highlight Show  
Pointer, and press ENTER to pause the screen movement.  
2. Use the ROCKER to move the pointer onto the target, such  
as underwater drop offs and stumps, you want to mark. The  
data window at the top of the screen displays the pointer’s  
depth, coordinates, bearing, and distance from your current  
location.  
Show Numbers Option  
3. Press ENTER/MARK. The New Waypoint Page appears  
with the waypoint’s coordinates, default three-digit name,  
and pointer depth automatically filled in.  
Change Numbers—allows you to specify the type of data  
displayed in each data field. For detailed instructions on changing  
the data fields, see page 31.  
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USING SONAR > SONAR PAGE  
Size Split—enables width adjustment of the Sonar Page split  
screen. This option is available only when a split screen zoom scale  
is selected. You can adjust the size of the split window anywhere  
from 1/4 to 3/4 width of the right half of the Sonar Page.  
Fish Symbols—determines how the Sonar Page displays  
underwater targets and background information. If you select off,  
the unit does not show fish symbols. If you select fish symbols,  
the Sonar Page shows only the information related to that symbol.  
Actual fish returns do not always appear as perfect arches (like  
in Simulator Mode), due to the speed, fish orientation, or other  
conditions.  
Double-Arrow  
Fish Symbols Off.  
Suspended targets displays as fish symbols. Background  
information is displayed.  
Size Split Menu Options  
Same as above with the target depth attached.  
Suspended targets display as fish symbols. No background  
information is displayed.  
Resizing the Split Sonar Display  
Same as above with target depth attached.  
Sonar Tab Options  
To access and change a setting on the Sonar tab:  
1. Press MENU twice to access the Main Menu. Use the  
ROCKER to highlight the Sonar tab.  
Water Type—because sound waves travel through Fresh and Salt  
water at different rates it is necessary to select the Water Type to  
ensure accurate readings on the unit.  
2. Using the ROCKER, highlight the field, and press ENTER.  
3. Highlight the setting, and press ENTER.  
4. Press QUIT to return to the Sonar Page or a previous page.  
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USING SONAR > SONAR TAB OPTIONS  
Depth Number—controls the efficiency of the digital depth update  
rate. Fast Update updates more quickly and is recommended for  
low-noise, deeper water (>50 ft). Auto is best for shallow water or  
high noise areas, and produces a slower screen update. Use Auto  
when you travel a wide variety of depths.  
Color Bar—shows a gradient scale of the current Target Level  
setting (see page 81).  
Depth Scale (Overlay)  
NOTE: If the unit is unable to track the bottom for any reason,  
the digits in the depth window flash on and off to alert you that  
the unit is not tracking the bottom.  
Color Bar  
Flasher  
Flasher—with the Flasher active, a graphic Flasher representation  
is displayed on the far right side of the graph. This graphic Flasher  
displays structure and bottom returns much the same as a true  
Flasher. This feature is particularly useful when using fish symbols.  
Main Menu—Sonar Tab  
Scale—controls the depth Scale displayed vertically along the right  
side of the graph. The depth Scale can be configured to display four  
different ways: as an Overlay, in the Corners, with Basic, or No  
Scale.  
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USING SONAR > SONAR TAB OPTIONS  
Keel Offset—used to offset the surface reading for the depth of  
a keel. This makes it possible to measure depth from the bottom  
of your keel instead of from the transducer’s location. Enter a  
positive number to offset for a keel, or enter a negative number to  
compensate for a large vessel that can draw several feet of water.  
The Keel Offset reflects in the depth reading.  
Background Color—sets the background color on the Sonar Page  
to Black, Blue, or White.  
Calibrate Water Speed—this is only available if you are using  
a speed-capable transducer/sensor. Calibration is required to  
ensure the Water Speed displayed on your unit is accurate. The  
unit automatically use the GPS ground speed, if it is available,  
for comparison on the calibration. If a GPS ground speed is not  
available, use either your boat’s speedometer reading (not always  
accurate) or a stopwatch to determine your speed over a certain  
distance (distance / time = speed). It is recommended that the  
calibration take place in water having little or no current.  
Keel Offset:  
Transducer at  
Surface Enter (+)  
positive number to  
show depth from  
bottom of keel  
Keel Offset: Transducer  
at Bottom of Keel Enter  
(-) negative number to  
show depth from surface  
Calibrating the  
Speed Sensor  
Map Split Sonar Detail—controls Map Page sonar split range  
scale. Full Range shows the entire scale of 2X or 4X left side split  
of Sonar Page. Maximum Detail displays what is shown on the left  
side of a split sonar screen.  
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USING SONAR > SONAR TAB OPTIONS  
To calibrate the water speed:  
1. On the Sonar tab, use the ROCKER to highlight Calibrate  
NOTE: If the boat is not moving fast enough or the speed  
sensor is not outputting a speed, the message “Boat Is Not  
Moving Fast Enough To Calibrate” appears at the bottom of  
the screen. Either verify the speed sensor wheel is moving, or  
safely increase boat speed. If there is a problem with the speed  
sensor/unit, or if a speed senor is not installed, a “Water Speed  
Sensor Is Not Working” message appears at the bottom of the  
screen. Check connections of speed sensor cables.  
Water Speed and press ENTER.  
2. Bring the boat to a cruising speed. The top ground and  
uncalibrated water speeds are shown at the bottom of the  
calibration window. Note your top water speed, then stop  
the boat and press ENTER.  
3. By default, the top ground speed automatically displays in  
the What was your top water speed? field. If a ground  
speed is not available, the top uncalibrated water speed is  
used instead. If the new speed is correct, highlight OK and  
press ENTER. If you want to manually enter a calibration,  
press ENTER on the speed field, enter a new speed, and  
then press ENTER.  
Page Defaults—restores the Sonar Page settings to the original  
factory setup.  
To restore default settings to the Sonar Tab:  
1. Press MENU.  
2. Highlight Page Defaults, and press ENTER.  
4. You can also press MENU on the calibration screen and  
choose Use Top Ground Speed to default back to ground  
speed or Use No Calibration to use the speed sensor’s  
uncalibrated speed.  
To restore default settings to the Sonar Tab:  
Press MENU. With Page Defaults highlighted, press  
ENTER.  
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USING SONAR > SONAR TAB OPTIONS  
Understanding the Sonar Display  
Understanding Sonar  
One of the first things to understand about sonar is that the  
transducer sends a beam down to the bottom of the water, much  
like the beam of a flashlight. The beam starts small near your  
vessel and expands as it gets to the bottom. Refer to “Transducer  
Coverage” for more detailed information.  
The transducer mounted on your vessel transmits sound waves  
toward the bottom of a lake, stream, or seabed in a cone-shaped  
pattern. When a transmitted sound wave strikes an underwater  
object—such as the bottom, a piece of structure, or a fish—sound  
is reflected back to the transducer. The transducer collects  
the reflected sound waves and sends the data to the GPSMAP  
188/188C Sounder to be processed and displayed. The underwater  
data is shown on the Sonar display in the order that it is returned:  
first returned is the first on the display.  
The Sonar Page does not display a three-dimensional representation  
of the underwater environment; the display is in two-dimensions,  
much like if you took a picture of an aquarium. Only the depth of  
the item in the water is displayed. The Sonar display does not show  
you where an item is located horizontally in the water, as shown in  
the drawings below. The fish is not directly above the tree in reality,  
but it can look like they are on the Sonar Page.  
Generally speaking, if the only thing between the transducer and  
the bottom is water, the first strong return comes from the bottom  
directly below the transducer and sets the bottom level. Weaker  
secondary returns provide the detailed data. Stronger returns  
display in darker colors, with red being the strongest return.  
Fish  
1'  
10'  
Tree  
Tree  
20'  
Aerial View of the Water  
Sonar Display  
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USING SONAR > UNDERSTANDING SONAR  
Transducer Coverage  
The area covered by the transmitted sound waves is determined  
by the cone angle of the transducer and the water depth. The wide  
cone angles (40°) associated with low frequencies (50 kHz) provide  
a large coverage area for finding fish within a coverage width that  
is approximately 2/3 of the water depth. However, this also means  
that wide cone angles produce less bottom detail and resolution.  
As shown in the drawing on the near right, the 40° cone angle  
produces a coverage area of approximately a 20-foot diameter  
circle at a 30-foot depth.  
Depth  
Coverage  
Diameter  
Coverage  
Diameter  
Depth  
The narrow cone angles (10°) associated with the high frequencies  
(200 kHz) provide better bottom resolution and crisper detail, but  
cannot show a large coverage area for finding fish. The 10° cone  
angle provides a coverage width that is approximately 2/10 of the  
water depth. As shown in the drawing on the far right, the 10° cone  
angle produces a coverage area of approximately a 6-foot diameter  
circle at a 30-foot depth.  
40° Cone Angle (50 kHz) 10° Cone Angle (200 kHz)  
Dual frequency mode combines both frequencies to get the best  
coverage area and contour/depth readings.  
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USING SONAR > UNDERSTANDING SONAR  
Whiteline  
Thermoclines  
When the sonar sound waves are reflected back by the bottom,  
a hard bottom returns a stronger signal than a soft bottom. A  
thin whiteline indicates a softer bottom, while a thick whiteline  
indicates a harder bottom. Normally, a red line is used to show the  
point where water meets the bottom. This line follows the bottom  
contour, along with any significant objects lying on the bottom.  
The unit uses the whiteline function to make the bottom layer  
information easier to distinguish.  
A rough definition of a thermocline is a break in water where  
the water temperature changes faster than the water above it.  
Thermoclines are shown as the weakest colors.  
One of the unique features offered by Garmin is See-Thru®  
technology, which allows the GPSMAP 188/188C Sounder to  
hear both weak and strong signals simultaneously so as to identify  
fish returns under the toughest conditions, such as suspended in  
thermoclines or even hiding near structures. See-Thru technology  
allows the transducer to see through thermoclines and locate fish.  
Thick  
Whiteline: Hard  
bottom  
Thermocline  
Whiteline On  
Whiteline Off  
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APPENDIX > SPECIFICATIONS  
GPS Accuracy:  
Position: <15 meters (49 feet), 95% typical*  
Velocity: 0.05 meters/sec steady state  
DGPS (USCG) Accuracy:  
APPENDIX  
Specifications  
Physical Specifications  
Size: 188: 6.2" H x 6.3" W x 2.6" D (15.8cm x 16.0cm x 6.6cm)  
Position: 3-5 meters (10-16 feet) with optional Garmin  
188C: 6.2" H x 6.3" W x 3.7" D (15.8 cm x 16.0 cm x 9.4 cm)  
DGPS receiver, 95% typical*  
Velocity: 0.05 meters/sec steady state  
DGPS (WAAS) Accuracy:  
Weight: 188: 1.7 lbs. (.77Kg); 188C: 2.6 lbs. (1.18 kg)  
Display: 188: 5.5" diagonal (14.1cm)  
Position: <3 meters (10 feet), 95% typical*  
Velocity: 0.05 meters/sec steady state  
Dynamics: 6g's  
188C: 5.0" diagonal (12.7cm) 16-color TFT display with  
backlighting (234 x 320 pixels)  
Case: Fully gasketed, high-impact plastic alloy, waterproof to IEC  
* Subject to accuracy degradation to 100 m 2DRMS under the U.S. DOD-imposed  
Selective Availability Program.  
529-IPX-7  
Power  
Temp. Range: 5°F to 158°F (-15°C to 70°C)  
Source: 188: 8-35 V DC; 188C: 10-35V DC  
Performance  
Usage: 188: 4 watts max. at 13.8 vDC;  
Receiver: Differential-ready 12 parallel channel WAAS capable  
188C: 10 watts max. at 13.8vDC  
receiver  
Fuse: 188: AGC/3 AG-2.0 Amp; 188C: AGC/3 AG-5.0 Amp  
Acquisition Times:  
Sonar  
Warm: Approx. 15 seconds  
Cold: Approx. 45 seconds  
AutoLocate: Approx. 2 minutes  
Sounder Power: 500 watts (RMS); 4000 watts (peak to peak)  
Frequency: 50/200 kHz (45°/15°)  
Depth: 1,500 foot max depth*  
Update Rate: 1/second, continuous  
* Depth capacity is dependent on water salinity, bottom type and other water conditions.  
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APPENDIX > INSTALLING THE GPSMAP 188/188C SOUNDER  
Installing the GPSMAP 188/188C Sounder  
The GPSMAP 188/188C Sounder must be properly installed  
according to the following instructions to get the best possible  
performance. To complete the installation, you need the appropriate  
fasteners and a 1" x 14-thread marine antenna mount available at  
most marine dealers.  
Suggested locations for mounting the external antenna.  
Mounting the GPS Antenna  
The Garmin antenna screws directly onto any standard 1" x 14-  
thread antenna mount. If you need to raise the antenna to avoid  
shading, try using a 1" x 14-thread extension mast available at most  
marine dealers.  
The antenna should be mounted in a location that has a clear,  
unobstructed view of the sky in all directions to ensure the best  
reception. Avoid mounting the antenna where it is shaded by the  
boat’s superstructure, a radome antenna, or mast. Sailboat users  
should avoid mounting the antenna high on the mast to prevent  
inaccurate speed readings caused by excessive heeling. Most  
marine VHF and LORAN antennas should not seriously degrade  
the GPS antenna’s reception. Never paint the antenna or clean it  
with harsh solvents.  
NOTE: It is possible to route the  
coaxial cable either through, or  
outside the antenna mount. It  
is possible to remove the BNC  
connector on the coaxial cable  
and the coaxial cable shortened  
to ease installation, however,  
doing so voids the antenna  
warranty. If the BNC connector  
is removed, it must be replaced  
with a new solder-on or crimp  
BNC connector.  
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APPENDIX > MOUNTING THE GPSMAP 188/188C SOUNDER  
To install the GPS antenna:  
1. Screw the antenna directly onto the 1 x 14-thread mount.  
Mounting the GPSMAP 188/188C Sounder  
Using the Gimbal Mount  
The GPSMAP 188/188C Sounder’s compact, waterproof case is  
suitable for mounting in exposed locations or at the nav station.  
The unit comes with a gimbal bracket that can be used for surface  
or overhead mounting. When choosing a location for the display  
unit, consider the following conditions:  
"
2. Route the cable to the mounting location of the display unit.  
Use the appropriate tie-wraps, fasteners, and sealant to  
secure the cable along the route and through any bulkhead  
or deck.  
3. After the GPSMAP 188/188C Sounder unit is installed,  
connect the cable to the antenna connector on the back of  
the display unit. Make sure that you turn the antenna cable  
connector 1/4 turn clockwise to lock the cable into place.  
There should be at least a 3" (7 cm) clearance behind the  
case to allow connection of the antenna and power/data  
cables.  
The mounting surface should be heavy enough to support the  
unit and protect it from excessive vibration and shock.  
NOTE: The temperature range for the GPSMAP 188/188C  
Sounder is 5°F to 158°F (-15°C to 70°C). Extended exposure  
to temperatures exceeding this range (in storage or operating  
conditions) can cause failure of the display. This type of  
failure and related consequences are NOT covered by the  
manufacturers limited warranty.  
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APPENDIX > MOUNTING THE GPSMAP 188/188C SOUNDER  
5. Screw the two mounting knobs through the bracket and into  
the display case.  
6. Connect the power/data and antenna cables (external  
antenna only) to the back of the unit, making sure the  
locking rings are fully tightened on both connectors.  
Flush Mounting the GPSMAP 188/188C Sounder  
The GPSMAP 188/188C Sounder can be flush mounted on a flat  
panel. When flush mounting the GPSMAP 188/188C Sounder, be  
sure to choose an appropriately sized location for the unit (see unit  
dimensions on page 92) and leave 1.25" (32 mm) clearance below  
the data card slot for inserting or removing data cards. Use the  
Flush Mount Template provided in the package with the GPSMAP  
188C. Use the instructions on the template to complete the flush  
mount installation.  
(GPSMAP 188C Shown)  
To install the GPSMAP 188/188C Sounder:  
1. Select a location for the mounting bracket.  
2. Mark and drill the four mounting holes for the fastener you  
are using.  
3. Fasten the bracket to the surface using the appropriate  
fastener.  
4. Insert the GPSMAP 188/188C Sounder into the mounting  
bracket. The bracket is designed for a tight fit to provide  
additional support when swiveling the unit.  
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APPENDIX > INSTALLING THE TRANSDUCER  
A wide cone angle transducer works best in shallow water. The  
wide cone angle provides a large coverage area, but at a decreased  
bottom resolution. In deeper water this can result in a large dead  
zone where fish cannot be seen. A narrow cone angle transducer  
is better suited to deep-water installations. The narrow cone angle  
provides a smaller viewing area (compared to a wide cone angle  
transducer at the same depth) with improved bottom resolution and  
a smaller dead zone. Dual frequency transducers give you the best  
of both wide and narrow cone angles.  
Installing the Transducer  
The transducer acts as the eyes and ears of your new sonar. Proper  
transducer installation is critical to the operation of your unit. The  
transducer transmits sound waves toward the bottom in a cone  
shape. The larger the cone angle, the larger the coverage area at a  
given depth.  
Wide cone angle  
A 50/200 kHz dual frequency 40°/10° cone angle, temperature  
sensing, transom mount transducer is included in the  
GPSMAP 188/188C Sounder (with transducer) package. This  
transducer provides good all-around performance.  
Narrow cone angle  
dead zone  
X
fish not seen  
X
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APPENDIX > INSTALLING THE TRANSDUCER  
Transom Mount Transducer  
The following diagram is for mounting the transducer included with the GPSMAP 188/188C Sounder with transducer package. If the  
transducer lead is too short, extension cables are available from your Garmin dealer. DO NOT cut the transducer lead or any part of the  
transducer cable, as this will void your warranty. The cable cannot be spliced and connected to any existing (Garmin or non-Garmin)  
transducer cables.  
NOTE: DO NOT mount the transducer behind strakes, struts, fittings, water intake, or discharge ports, or anything that creates air bubbles or  
causes the water to become turbulent. It is important that the transducer is in clean (non-turbulent) water for optimal performance.  
Mount the transducer cable cover�  
well above the waterline.  
Apply marine sealant to all�  
screw threads to prevent water�  
from seeping into the transom.  
Transducer should extend 1/8" below�  
fiberglass hull or 3/8" below aluminum hull  
Make sure that the transducer is�  
below water level when the boat �  
is on plane at high speed  
OK  
Do not mount transducer directly in the �  
path of the prop. The transducer can cause�  
cavitation that may degrade the boat's performance �  
and damage the prop.  
Mount the transducer parallel with the bottom.  
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APPENDIX > CONNECTING THE POWER/DATA CABLE  
Connecting the Power/Data Cable  
The power/data cable connects the GPSMAP 188/188C Sounder to a DC system and provides interface capabilities for connecting external  
devices. The color code in the diagram below indicates the appropriate harness connections. Replacement fuse for the GPSMAP 188  
AGC/3AG - 2 Amp fuse and a AGC/3AG - 5 Amp fuse for the GPSMAP 188C.  
NOTE: During a typical installation, only the Red and Black wires are used. The other wires do not have to be connected for normal  
operation of the unit.  
 
�  
 
�  
�  
�  
�  
 
 
 
100 ma  
Max Coil Current  
 
��  
�  
 
�  
�  
Pin 14  
Pin 13  
Pin 11  
Pin 15  
�  
�  
�  
 
 
Pin 18  
Pin 16  
Pin 17  
�  
�  
�  
PIN 11 (yellow) Alarm Low  
�  
 
�  
PIN 13 (white) NMEA IN (Com 2 RX)  
PIN 14 (green) NMEA OUT (Com 2 TX)  
PIN 15 (red) Power  
�  
�  
�  
PIN 16 (brown) NMEA IN (Com 1 RX)  
PIN 17 (blue) NMEA OUT (Com 1 TX)  
�  
�  
�  
 
�  
PIN 18 (black) Ground  
�  
���  
��  
98  
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APPENDIX > INTERFACING  
The GPSMAP 188/188C Sounder also includes NMEA input with  
support for the WPL sentence and sonar NMEA input with support  
for the DPT (Depth), MTW (Water Temp) and VHW (Water Speed  
& Heading) sentences. If connecting to COM 2 for sonar NMEA  
input, the unit interface must be set to NMEA In/NMEA Out. If  
connecting to COM 1, the unit must be set to NMEA In/NMEA  
Out.  
Interfacing  
The following formats are supported for connection of external  
devices:  
Garmin proprietary Differential GPS (DGPS), NMEA 0183  
versions 3.0, ASCII Text Output, RTCM SC-104 input (vs. 2.0).  
The following are the sentences for NMEA 0183, vs. 3.0 output:  
You can download a copy of Garmin’s proprietary communication  
protocol on the Support section of our Web site at  
www.garmin.com.  
Approved sentences—GPRMC, GPGGA, GPGSA, GPGSV,  
GPGLL, GPBOD, GPRTE, and GPWPL.  
Proprietary sentences—PGRME, PGRMZ, and PSLIB. The  
GPSMAP 188/188C Sounder accepts NMEA input with support for  
the DBT, DPT, MTW, and VHW sentences.  
Complete information regarding NMEA and RTCM formats is  
available for purchase at www.nmea.org  
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APPENDIX > INSTALLING AND REMOVING DATA CARDS  
To remove a data card:  
1. Open the card door by pressing together on the two handles  
Installing and Removing Data Cards  
The GPSMAP 188/188C Sounder uses optional Garmin marine  
BlueChart and MapSource data cards to display digital charts and  
maps on-screen. Data cards are installed in the card slot located at  
the bottom right of the unit. Data cards can be installed or removed  
at any time, whether the unit is on or off.  
at the bottom of the door and lifting it up and open.  
2. Grasp the card handle at the bottom and pull down firmly.  
3. If the unit is on, a confirmation tone sounds when the data  
card is removed.  
To install a data card:  
1. Open the card door by pressing together on the two handles  
at the bottom of the door and lifting it up and open.  
2. Insert the card, with the label facing front and the handle  
bottom, into the slot.  
3. Firmly push the card into the unit. It in not necessary to  
force the card and about 1/2 is still exposed when it is  
"
properly inserted. If the unit is on, a confirmation tone  
sounds and a message displays on-screen noting the card  
details when the card is properly installed and accepted.  
4. Close the cover.  
The first time you insert a data card, the unit takes a few seconds to  
read the card.  
If you insert a data card and get a “card format not recognized”  
message, try removing the card and reinserting it. If the card is still  
not recognized, contact Garmin Product Support or your Garmin  
dealer for assistance. Data cards are not waterproof and should  
not be exposed to moisture or excessive static charges. Data cards  
should be stored in the case supplied with the card.  
After the data card is read, a summary screen appears. Press  
ENTER to acknowledge.  
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APPENDIX > SATELLITE INFORMATION  
Satellite Strength Indicator Bars  
Satellite Information  
The Satellite Strength Indicator Bars show the strength of the  
signal being received, and the status of the signal. The bars are  
either shaded or filled. The gray bar means the GPS is in the  
process of storing orbital data it is receiving from the satellite  
signal. When the bar turns solid, the GPS is using the satellite  
signal for navigation. A “D” in or above the bar means that  
differential corrections (WAAS or DGPS) are being applied to that  
satellite.  
Center dot - 90°  
above the horizon  
90°  
Inner ring- 45°  
above the horizon  
Outer ring -  
the horizon  
45°  
Satellite Sky View  
Date, Time, and Current Location  
The GPS gets date and time information from the satellite’s on-  
board atomic clock. When the GPS receiver has achieved a 2D or  
3D GPS location, the current location is displayed in the selected  
location format.  
Satellite Location  
The location of each available satellite is displayed over two  
location rings on the Satellite Information Page. The outer ring  
represents the horizon, the inner ring represents 45° above the  
horizon, and the center represents directly overhead. When the unit  
is using a satellite for navigation, the satellite number is highlighted  
on the location rings. The unit can be set to display satellite  
location with North or your current track at the top of the display.  
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APPENDIX > WHAT IS A WAAS AND DGPS?  
What is WAAS?  
What is Differential GPS (DGPS)?  
The Wide Area Augmentation System (WAAS) is an F.A.A. funded  
project to improve the overall integrity of the GPS signal. It is  
a space-based system that broadcasts integrity information and  
correction data as determined by ground reference stations. WAAS  
testing completed in September of 2003 confirmed an accuracy of 2  
to 3 vertical meters throughout the majority of the continental U.S.  
and portions of Alaska. For more information, go to  
The U.S. and Canadian governments (among others) have set up  
Differential GPS (DGPS) stations to transmit correction signals.  
They are operational in coastal areas and on many navigable river  
systems. The DGPS system is available for use without a fee.  
Refer to the U.S. Coast Guard’s Web site, http://www.uscg.gov/  
for locations and the status of the differential sites. Using DGPS  
requires additional equipment.  
http://gps.faa.gov/Programs/WAAS/waas.htm.  
NOTE: If you are using the GPSMAP 188/188C Sounder  
outside of the U.S.A, we recommend you turn off WAAS for the  
most accurate location fix.  
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APPENDIX > WHAT IS MMSI?  
U.S Non-Federal User: Commercial users, or those who travel  
outside the U.S. or Canada, must apply for a ship station license, or  
an amendment to a ship station license. To find out if you require  
a Ship Station license contact: http://wireless.fcc.gov/marine/  
fctsht14.html. If your vessel requires licensing by the FCC you  
obtain a MMSI during the application/licensing process when you  
file FCC Forms 159 and 605.  
What is Maritime Mobile Service Identity  
(MMSI)?  
Maritime Mobile Service Identity (MMSI) basically allows a VHF  
radio to act like a phone. In order to make a “call” on a phone,  
you first need a phone number to dial. The 9 digit MMSI number  
acts like a phone number when used in a Position Report and as a  
unique identifier to the Coast Guard when used in an emergency  
Distress Call. In order to obtain a Maritime Mobile Service Identity  
(MMSI) number, users must register their VHF radio with the FCC  
(Form 605). Garmin does not supply this number.  
U.S. Federal User: Federal users can obtain MMSI assignments  
from their agency radio spectrum management office. These  
procedures are currently under review by the NTIA (National  
Telecommunications and Information Administration).  
How are MMSI Assignments Obtained?  
Non-commercial users (for example, recreational users who remain  
in domestic waters and only carry VHF, EPIRB (Emergency  
Position Indicating Radio Beacons), and Radar) are not required to  
have a FCC ship station license. The FCC and Coast Guard have  
authorized some second and third party vendors to assign MMSI  
numbers. This service is limited to registering recreational vessels  
only. To receive information on how to obtain a recreational MMSI  
number, contact: http://www.uscg.mil/rescue21/links/mmsi.htm or  
http://wireless.fcc.gov/marine/.  
Outside the U.S.: Users can obtain an MMSI assignment from their  
telecommunications authority or ship registry, often by obtaining or  
amending their ship station license.  
In Canada: Industry Canada is responsible for assigning MMSI  
numbers to commercial and recreational vessels. Information is  
available at the following web site: http://apollo.ic.gc.ca/english/  
mmsi.html.  
For information regarding MMSI’s visit:  
http://www.uscg.gov/marcomms/gmdss/mmsi.htm.  
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APPENDIX > NAVIGATION TERMS  
ETA at Destination—the time you estimate to reach a Go To  
destination or the final waypoint in a route.  
Navigation Terms  
Avg Speed—the average of all second-by-second speed readings  
since last reset.  
ETA at Next—the time you estimate to reach a Go To destination  
or the next waypoint in a route.  
Bearing (BRG)—the compass direction from your current location  
to a destination.  
Fuel—the fuel required to travel from current location to the  
indicated route waypoint.  
Course—the course between the active from and to waypoints.  
GPS Accuracy—estimated accuracy of the GPS position.  
Leg Dist—the distance between two route waypoints.  
Depth—the depth below transducer. This field is active only if a  
transducer is connected to the GPSMAP 188/188C Sounder.  
Leg Fuel—the fuel required to travel from a route waypoint to the  
Distance (Dist)—the distance from the current location to a  
next waypoint (in sequence) in the route.  
destination.  
Leg Time—the time required to travel from a route waypoint to the  
Dist to Destination—the distance from the current location to a Go  
next waypoint (in sequence) in the route.  
To destination, or the final waypoint in a route.  
Max Speed—the maximum second-by-second speed recorded  
Dist to Next—the distance from current location to a Go To  
since last reset.  
destination, or the next waypoint in a route.  
Moving Average Speed—average speed while the unit is moving.  
Moving Trip Timer—total time the unit has been moving.  
DOP (Dilution of Precision)—reflects the quality of the GPS  
signals and satellite geometry.  
Elevation—height above mean sea level (MSL).  
Odometer—a running tally of distance travelled, based on the  
distance between second-by-second position readings.  
ETA (Estimate Time of Arrival)—The time you estimate to reach  
your destination waypoint, based on current speed and track.  
Off Course—the distance you are off course in either direction,  
left or right.  
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APPENDIX > NAVIGATION TERMS  
Pointer—an arrow pointing to your destination.  
Total Average Speed—average speed of unit for both moving and  
stopped speeds since last timer reset.  
Speed—the current velocity at which you are travelling, relative to  
a ground position. Also referred to as ground speed.  
Total Trip Timer—total time the unit has been in operation since  
last reset of the trip timers.  
Sunrise—the current day’s time of sunrise.  
Sunset—the current day’s time of sunset.  
Time Of Day—the current time.  
Turn—the angle difference between the bearing to your destination  
and your current track. “L” indicates you should turn left; “R”  
indicates you should turn right.  
Time To—the estimated time required to reach a Go To  
destination, or the next waypoint in a route. Also known as  
“estimated time en route.”  
VMG (Velocity Made Good)—the speed you are closing in on a  
destination along a course. Also referred to as the vector velocity to  
your destination.  
Time to Dest—the estimated time required to reach a Go To  
Voltage—current voltage reading being received by unit.  
destination, or the final waypoint in a route.  
Water Speed—the speed through the water. This field is only  
active if the GPSMAP 188/188C Sounder is receiving speed  
readings from a NMEA device.  
Time to Next—the estimated time required to reach a Go To  
destination, or the next waypoint in a route.  
To Course—the recommended direction to steer to reduce course  
error or stay on course. Provides the most efficient heading to get  
back to the course and proceed along your route.  
Water Temp—the water temperature. This field is only active if  
the GPSMAP 188/188C Sounder is receiving speed readings from  
a NMEA device.  
Track—the direction of movement relative to a ground position.  
Waypoint Destination—the final waypoint in the route, or the  
Also referred to as “ground track.”  
destination waypoint.  
Trip Odometer—a running tally of distance travelled since last  
Waypoint Next—the next waypoint in the route.  
reset. See also “Odometer.”  
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APPENDIX > MESSAGES  
No Diff GPS Location—RTCM is selected but no DGPS data is  
being received.  
Messages  
Approaching Turn—you are nearing a turn in a route.  
No Tide Stations for that Area—no tide stations within 100 miles  
of the area.  
Arriving at Destination—you are nearing your destination.  
Batteries Low—you have less than 10 minutes of battery left.  
None Found—no data matched the search criteria.  
Can’t Unlock Maps—no applicable unlock code for one or more  
maps was found.  
Off Course—you are off course the distance set in the “Off  
Course” alarm.  
Cannot display all found, use city, or postal code—the unit  
found too many items to display. Narrow the search using the city  
or postal code.  
Proximity Memory Full—no additional proximity waypoints can  
be saved.  
Proximity Radius Overlaps—the radii of two proximity  
waypoints overlap.  
Database Error—internal problem with the unit. Contact your  
dealer or Garmin Product Support to have the unit repaired.  
Route Already Exists—you have entered a route name that  
already exists.  
Deep Water—the water is deeper than the amount set in the Deep  
Water Alarm.  
Route Memory Full—no additional routes can be saved.  
Dragging Anchor—the distance set in the Anchor Alarm is  
exceeded.  
Route Truncated—uploaded route from another device has more  
than 50 (188) or 254 (188C) waypoints.  
Lost Satellite Reception—the unit is unable to continue receiving  
satellite signals.  
Route Waypoint Memory Full—no additional route waypoints  
can be saved.  
Memory Full—unit memory is full; no further data can be saved.  
Near Proximity Point—you are nearing a proximity waypoint.  
Shallow Water—the water is shallower than the depth set in the  
Shallow Water Alarm.  
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APPENDIX > MESSAGES  
Track Already Exists—a saved track with the same name already  
Track Truncated—a complete uploaded track does not fit in  
exists.  
memory. The oldest track log points have been deleted.  
Track Memory Full—no more track data can be stored without  
Transfer Complete—data transfer has been completed.  
deleting old data.  
Waypoint Already Exists—a waypoint with the same name  
Track Log Full—the track log is full and track recording has been  
turned off. To record more track points, you need to clear the track  
log and turn track recording on. This is only displayed when the  
track recording setting is set to “Stop When Full.”  
already exists.  
Waypoint Memory Full—the unit has stored the maximum  
number of waypoints.  
GPSMAP 188/188C Sounder Owner’s Manual  
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APPENDIX > LORAN TD SYSTEM  
LORAN TD Feature  
LORAN TD System  
The LORAN TD (Time Delay) feature eases the transition from  
using LORAN to using GPS. The GPSMAP unit automatically  
converts GPS coordinates to LORAN TDs for those who have a  
collection of LORAN fixes for favorite fishing spots and other  
waypoints recorded as TDs. You can display your position as a TD  
or enter waypoints as TDs. The accuracy to be expected from this  
conversion is approximately 30 meters. When the unit is placed  
in the LORAN TD format mode, it simulates the operation of a  
LORAN receiver. Position coordinates can be displayed as TDs,  
and all navigation functions can be used as if the unit was actually  
receiving LORAN signals.  
LORAN C is a radio navigation aid operated and maintained in the  
United States by the United States Coast Guard. The name LORAN  
is an acronym for “LOng RAnge Navigation.” The LORAN system  
covers the entire United States and the U.S. Coastal Confluence  
Zone. From the perspective of a mariner, the system is used for  
ocean and coastal navigation. It can be used as a supplemental  
system for harbor and harbor approach navigation, and it is used  
for inland navigation by recreational vehicles.  
Using the LORAN TD Format  
When creating new waypoints using LORAN TD coordinates,  
you must set the correct LORAN chain number and secondary  
stations in the Setup TD field before storing the waypoint. After  
the waypoint is stored in unit memory, it always references the  
LORAN chain number and secondary stations currently selected in  
the Setup TD field. If you enter a different LORAN chain number  
or change the secondary stations or offsets in the Setup TD field,  
the active waypoint information reflects those changes. Because  
the GPSMAP 188/188C does not rely on the LORAN signal for  
navigation, it can reference a different GRI chain and/or secondary  
stations and still navigate to the location stored in memory.  
GPSMAP 188/188C Sounder Owner’s Manual  
Change to Loran TD from the Units  
tab on the Main Menu.  
108  
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APPENDIX > LORAN TD SYSTEM  
The LORAN Position Format field is located on the Setup–  
Location tab on the Main Menu. The LORAN TD Setup window  
contains the fields to select the Loran GRI-Chain Number, Primary  
and Secondary Stations, and TD Offsets.  
If the active GRI Chain, secondary stations, or offsets were  
changed since the waypoint was created, the waypoint now  
references the active GRI-chain and secondary stations. You must  
adjust the TD coordinates accordingly. Remember that the GPS  
is not relying on the LORAN signal for navigation and actually  
converts the TD coordinate to a useful LAT/LON coordinate before  
storing the waypoint to memory or using it for navigation. Because  
of this, the unit can navigate to a TD coordinate anywhere in the  
world.  
To set up Loran TD from the Main Menu:  
1. Press MENU twice to display the Main Menu.  
2. Using the ROCKER, highlight the Position Format field on  
the Units tab, and press ENTER.  
3. Highlight Loran TD, and press ENTER  
.
You must know your GRI chain number and secondary stations  
to create a LORAN TD position. For more information, read  
our LORAN TD Position Format Handbook, available from the  
Garmin Web site (www.garmin.com/support/userManual.jsp.)  
4. Highlight Setup, and press ENTER.  
5. To change the settings of any of the five fields, highlight the  
field, and press ENTER. Select or enter a setting, and then  
press ENTER.  
6. When finished, highlight Save, and press ENTER.  
Loran TD Setup Page  
GPSMAP 188/188C Sounder Owner’s Manual  
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APPENDIX > OPTIONAL ACCESSORIES  
Programmable Data Cards—blank data cards are available  
in 8 MB, 16 MB, 32 MB, 64 MB, 128 MB, and 256 MB sizes.  
Download street-level map detail, points of interest, business  
addresses and phone numbers, marine data, topographical  
information, and more from MapSource CD-ROMs to a data card,  
either directly through your GPSMAP 188/188C Sounder using the  
PC Interface Cable, or with the Data Card Programmer.  
Optional Accessories  
The following optional accessories are designed to enhance the  
operation of the GPSMAP 188/188C Sounder.  
To obtain replacement parts and optional accessories, contact your  
Garmin Dealer, Garmin Product Support in the U.S.A. at  
800-800-1020, or Garmin Europe at 44-0870-8501241.  
WARNING: Garmin accessories have been designed and  
specifically tested for use with Garmin products. Accessories  
offered by other manufacturers have not been tested or  
approved for use with Garmin products. Use of such  
accessories could cause damage to the GPSMAP 188/188C  
Sounder and void the warranty.  
USB Data Card Programmer—programs blank data cards at high  
speed through a PC.  
Pre-Programmed Data Cards—data cards pre-programmed with  
either Garmin BlueChart, Recreational Lakes with Fishing Hot  
Spots or Minnesota LakeMaster ProMap chart/ data.  
A/C Adapter—powers the unit using a standard AC house current.  
MapSource Software CD-ROMs—enhances the basemap,  
create waypoints and routes from your PC. MapSource offers  
several detailed mapping options that are compatible with the  
GPSMAP 182/182C, including MetroGuide, Recreational Lakes  
with Fishing Hot Spots, and Minnesota LakeMaster ProMap.  
PC Interface Cable with vehicle Power Adapter—connects  
the GPSMAP 188/188C Sounder to a vehicle’s electrical system  
on one end, and a PC, beacon receiver, marine autopilot, or other  
compatible device on the other end.  
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APPENDIX > SOFTWARE LICENSE AGREEMENT AND PRODUCT REGISTRATION  
Software License Agreement  
Product Registration  
BY USING THE GPSMAP 188/188C SOUNDER, YOU AGREE  
TO BE BOUND BY THE TERMS AND CONDITIONS OF THE  
FOLLOWING SOFTWARE LICENSE AGREEMENT. PLEASE  
READ THIS AGREEMENT CAREFULLY.  
Help us better support you by completing our online registration  
today! Have the serial number of your GPSMAP 188/188C  
Sounder handy and connect to our Web site (http://www.garmin.  
com). Look for the Product Registration link on our Home page.  
Garmin grants you a limited license to use the software embedded  
in this device (the “Software”) in binary executable form in the  
normal operation of the product. Title, ownership rights, and  
intellectual property rights in and to the Software remain in  
Garmin.  
Use this area to record the serial number (8-digit number located on  
the back of the box) in case your GPSMAP 188/188C Sounder unit  
is lost, stolen, or needs service. Be sure to keep your original sales  
receipt in a safe place or attach a photocopy inside the manual.  
Serial Number: ___ ___ ___ ___ ___ ___ ___ ___  
You acknowledge that the Software is the property of Garmin and  
is protected under the United States of America copyright laws  
and international copyright treaties. You further acknowledge  
that the structure, organization, and code of the Software are  
valuable trade secrets of Garmin and that the Software in source  
code form remains a valuable trade secret of Garmin. You agree  
not to decompile, disassemble, modify, reverse assemble, reverse  
engineer, or reduce to human readable form the Software or any  
part thereof or create any derivative works based on the Software.  
You agree not to export or re-export the Software to any country  
in violation of the export control laws of the United States of  
America.  
Contact Garmin  
If you should encounter any difficulty while using your  
GPSMAP 188/188C Sounder, or if you have any questions, in the  
U.S.A. contact Garmin Product Support by phone: 913-397-8200  
or 800-800-1020, Monday–Friday, 8 AM–5 PM Central Time, or  
by e-mail at sales@garmin.com.  
In Europe, contact Garmin (Europe) Ltd. at 44-0870.8501241.  
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APPENDIX > LIMITED WARRANTY  
packed with the tracking number clearly written on the outside of the package.  
The unit should then be sent, freight charges prepaid, to any Garmin warranty  
service station. A copy of the original sales receipt is required as the proof of  
purchase for warranty repairs.  
Limited Warranty  
This Garmin product is warranted to be free from defects in materials or  
workmanship for one year from the date of purchase. Within this period,  
Garmin will at its sole option repair or replace any components that fail in  
normal use. Such repairs or replacement will be made at no charge to the  
customer for parts or labor, provided that the customer shall be responsible for  
any transportation cost. This warranty does not cover failures due to abuse,  
misuse, accident or unauthorized alteration or repairs.  
Garmin International, Inc.  
1200 E 151st Street, Olathe, Kansas 66062 U.S.A.  
Tel. 913/397.8200  
Fax. 913/397.8282  
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE  
EXCLUSIVE AND IN LIEU OF ALL OTHER WARRANTIES EXPRESS  
OR IMPLIED OR STATUTORY, INCLUDING ANY LIABILITY ARISING  
UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS  
FOR A PARTICULAR PURPOSE, STATUTORY OR OTHERWISE. THIS  
WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, WHICH MAY  
VARY FROM STATE TO STATE.  
Garmin (Europe) Ltd.  
Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9DL  
U.K.  
Tel. 44/0870.8501241  
Fax 44/0870.8501251  
Online Auction Purchases: Products sold through online auctions are not  
eligible for rebates or other special offers from Garmin. Online auction  
confirmations are not accepted for warranty verification. To obtain warranty  
service, an original or copy of the sales receipt from the original retailer is  
required. Garmin will not replace missing components from any package  
purchased through an online auction.  
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL,  
SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES, WHETHER  
RESULTING FROM THE USE, MISUSE, OR INABILITY TO USE THIS  
PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not  
allow the exclusion of incidental or consequential damages, so the above  
limitations may not apply to you.  
International Purchases: A separate warranty is provided by international  
distributors for units purchased outside the United States. This warranty is  
provided by the local in-country distributor and this distributor provides  
local service for your unit. Distributor warranties are only valid in the area of  
intended distribution. Units purchased in the United States or Canada must  
be returned to the Garmin service center in the United Kingdom, the United  
States, Canada, or Taiwan for service.  
Garmin retains the exclusive right to repair or replace the unit or software  
or offer a full refund of the purchase price at its sole discretion. SUCH  
REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE REMEDY FOR  
ANY BREACH OF WARRANTY. To obtain warranty service, contact your  
local Garmin authorized dealer or call Garmin Product Support for shipping  
instructions and an RMA tracking number. The unit should be securely  
112  
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APPENDIX > FCC COMPLIANCE  
The Garmin GPSMAP 188/188C Sounder has no user-serviceable parts.  
Should you ever encounter a problem with your unit, please take it to an  
authorized Garmin dealer for repairs.  
installation. If this equipment does cause harmful interference to  
radio or television reception, which can be determined by turning  
the equipment off and on, the user is encouraged to try to correct  
the interference by one of the following measures:  
The GPSMAP 188/188C Sounder is fastened shut with screws. Any attempt to  
open the case to change or modify the unit in any way will void your warranty  
and may result in permanent damage to the equipment.  
Reorient or relocate the receiving antenna.  
Increase the separation between the equipment and the  
receiver.  
FCC Compliance  
The GPSMAP 188/188C Sounder complies with Part 15 of the  
FCC interference limits for Class B digital devices FOR HOME  
OR OFFICE USE. These limits are designed to provide more  
reasonable protection against harmful interference in a residential  
installation, and are more stringent than “outdoor” requirements.  
Connect the equipment into an outlet on a circuit different  
from that to which the receiver is connected.  
Consult the dealer or an experienced radio/TV technician  
for help.  
The GPSMAP 188/188C Sounder does not contain any user-  
serviceable parts. Repairs should only be made by an authorized  
Garmin service center. Unauthorized repairs or modifications  
could result in permanent damage to the equipment, and void your  
warranty and your authority to operate this device under Part 15  
regulations.  
Operation of this device is subject to the following conditions: (1)  
This device may not cause harmful interference, and (2) this device  
must accept any interference received, including interference that  
may cause undesired operation.  
This equipment generates, uses, and can radiate radio  
frequency energy and may cause harmful interference to radio  
communications if not installed and used in accordance with the  
instructions. However, there is no guarantee that interference will  
not occur in a particular  
GPSMAP 188/188C Sounder Owner’s Manual  
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APPENDIX > SAFETY INFORMATION  
MAP DATA INFORMATION: One of the goals of Garmin is to provide  
customers with the most complete and accurate cartography that is available  
to us at a reasonable cost. We use a combination of governmental and private  
data sources, which we identify as required in product literature and copyright  
messages displayed to the consumer. Virtually all data sources contain  
inaccurate or incomplete data to some degree. This is particularly true outside  
the United States, where complete and accurate digital data is either not  
available or prohibitively expensive.  
Safety Information  
CAUTION: Use the GPSMAP 188/188C Sounder at your own risk. To  
reduce the risk of unsafe operation, carefully review and understand all  
aspects of this Owner’s Manual—and thoroughly practice operation using  
Simulator Mode prior to actual use. When in actual use, carefully compare  
indications from the GPSMAP 188/188C Sounder to all available navigation  
sources, including information from other NAVAIDs, visual sightings, charts,  
etc. For safety, always resolve any discrepancies before continuing navigation.  
WARNING: The Global Positioning System (GPS) is operated by the  
United States government, which is solely responsible for its accuracy  
and maintenance. The system is subject to changes which could affect the  
accuracy and performance of all GPS equipment. Although the Garmin  
GPSMAP 188/188C Sounder is a precision electronic NAVigation AID  
(NAVAID), any NAVAID can be misused or misinterpreted, and therefore  
become unsafe.  
CAUTION: IT IS THE USER’S RESPONSIBILITY TO USE THIS  
PRODUCT PRUDENTLY. THIS PRODUCT IS INTENDED TO BE USED  
ONLY AS A NAVIGATIONAL AID AND MUST NOT BE USED FOR ANY  
PURPOSE REQUIRING PRECISE MEASUREMENT OF DIRECTION,  
DISTANCE, LOCATION OR TOPOGRAPHY. THIS PRODUCT SHOULD  
NOT BE USED TO DETERMINE GROUND PROXIMITY FOR  
AIRCRAFT NAVIGATION.  
WARNING: This product, its packaging, and its components contain  
chemicals known to the State of California to cause cancer, birth defects,  
or reproductive harm. This Notice is being provided in accordance with  
California’s Proposition 65. If you have any questions or would like additional  
information, please refer to our Web site at http://www.garmin.com/prop65.  
CAUTION: The electronic chart is an aid to navigation and is designed to  
facilitate the use of authorized government charts, not replace them. Only  
official government charts and notices to mariners contain all information  
needed for save navigation—and, as always, the user is responsible for their  
prudent use.  
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INDEX  
Anchor Drag Alarm 76  
Arrival Alarm 76  
Delete  
DSC Directory Item 24  
Depth Line 82  
DGPS 102  
Fish Alarm 76  
Flasher 86  
INDEX  
B
G
Gain 81  
Symbols  
2D Differential 42  
2D GPS Location 89, 101  
3D Differential 42  
3D GPS Location 101  
BackLight 4  
Base Map 64  
Battery Alarm 76  
Bearing Line 67  
Bottom Split 81  
Alarm 76  
Garmin Data Transfer 72  
Go To 13  
Distress Call 25  
Position Report 25  
GPS Tab 39  
Options 43  
Differential GPS 102  
Dilution of Precision 104  
Distance 60  
Distress Calls 22, 2225  
DOP 104  
A
C
Accessories 110  
Accuracy 39  
Accuracy Alarm 76  
Accuracy Circle 67  
Active Route Page 37  
Options 38  
DSC 22  
Card Tab 62  
Call List 24  
Directory 24  
Log 24  
Celestial Tab 47  
Cleaning iv  
H
Heading Line 67  
Highway Page 35  
Options 36  
Setup 37  
Clock Alarm 76  
Color Mode 64  
Communication Tab 72  
Correction Signals 102  
Course Line 67  
Course Up 64  
Setting Up 25  
DSC Tab 61  
Alarms  
Highway Tab 68  
Accuracy 76  
Anchor Drag 76  
Arrival 76  
E
Edit  
I
Route 56  
Waypoint 11  
Enter/Mark Key 5, 8  
Initializing 1  
Installation 93  
Interface Keys 5  
Interfacing 99  
In Zoom Key 5  
Battery 76  
D
Clock 76  
DGPS 76  
DSC 25  
Fish 76  
Data Cards 100  
Data Entry 6  
Data Fields  
F
FCC Compliance 113  
Features 5  
Change Numbers 31  
Show 31  
Split Fields 35  
Date/Time 101  
Daylight Saving Time 62  
Off Course 76  
Shallow/Deep Water 76  
Temperature 76  
Alarm Tab 76  
K
Find 19  
Additional Information 21  
Find Key 5, 19  
Keel Offset 87  
Keypad Usage 5  
Key Beeps 69  
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115  
 
INDEX  
Power Key 5  
Power On/Off 1  
Proximity Waypoints 52  
Simulator Mode 3, 114  
Sonar 78  
L
N
Language 69  
License Agreement 111  
LORAN TD 108  
NAV/MOB Key 5, 12  
Navaids 66  
Depth Line 82  
Gain 81  
Noise Reject 82  
Understanding 89  
View/Span 81  
Whiteline 82  
Navigating 12  
Distress Call 25  
Go To 13  
Q
Quit Key 5  
M
Magnetic Variation 71  
Main Menu 39  
Main Pages 26  
Man OverBoard 10  
MapSource 62  
Position Report 25  
Routes 53  
R
Receiving a DSC Call 25  
Replace From Card 62  
Review  
Sonar Page 78  
Adjustment Menu 79  
Bottom Split 81  
Options 83  
TracBack 14  
Navigation Terms 104  
Nav Key 5  
DSC Call 23  
Waypoints 11  
Rocker Key 5  
Routes 17  
Map Data Information 114  
Map Datum 70  
Map Detail 64  
Map Information Page 65  
Map Page 27  
NMEA 74  
Sonar Tab 68  
Noise Reject 82  
North Up 64  
Numbers Page 34  
Options 85  
Specifications 92  
Speed Filter 69  
Spot Sounding 66  
Storage iv  
System Information 69  
System Tab 69  
Copy 53  
Create 17  
Delete 53  
Delete All 53  
Edit 56  
Options 30  
Setup Map 33  
O
Off Course Alarm 76  
Orientation 64  
Out Zoom Key 5  
Overzoom 29  
Map Pointer 7, 28  
Map Scales 29  
Map Tab 64  
Maritime Mobile Service Identity 103  
Mark Key 5  
Measure Distance 32  
Menu Key 5  
Merge From Card 62  
Messages 106  
MMSI 22, 103  
MOB 10  
MOB Key 5  
Routes Tab 53  
Route Review Page 54  
Options 55  
T
P
Temperature Scale 68  
Temperature Tab 68  
Thermoclines 91  
Tide Stations 43  
Tide Tab 43  
RTCM 74  
Pages Tab 63  
Page Key 5  
S
Pointer Page 33  
Options 34  
Points Tab 48  
Position Format 70  
Position Reports 23  
Safety Information 114  
Satellite Location 101  
Satellite Sky View 101  
Selecting Options 6  
Shallow/Deep Water Alarm 76  
Time Format 62  
Time Tab 62  
Time Zone 62  
116  
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INDEX  
TracBack 14  
Activate 16  
Track Logs  
Move 12  
Proximity 52  
Reviewing 11  
Underwater 84  
Clear 15  
Save 15  
Waypoint Lists  
Track Tab 59  
Active 59  
Proximity 51  
User 49  
Saved 59  
Whiteline 82, 91  
Wide Area Augmentation System 40,  
Track Up 64  
Transducer 90, 96  
Trip Planning 58  
Trip Tab 46  
Wiring Installation 98  
Z
U
Zoom Keys 5  
Zoom Range 29  
Zoom Settings 29  
Underwater Waypoints 84  
Units Tab 70  
Unit Defaults 69  
W
WAAS 40, 102  
Disable/Enable 41  
Waterproof iv  
Water Speed 87  
Water Temperature Alarm 76  
Waypoints  
Creating 8  
Creating Graphically 9  
Editing 11  
Enter/Mark 8  
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117  
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For the latest free software updates (excluding map data) throughout the life of your  
Garmin products, visit the Garmin Web site at www.garmin.com.  
© Copyright 2005 Garmin Ltd. or its subsidiaries  
Garmin International, Inc.  
1200 East 151st Street, Olathe, Kansas 66062, U.S.A.  
Garmin (Europe) Ltd.  
Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9DL, U.K.  
Garmin Corporation  
No. 68, Jangshu 2nd Road, Shijr, Taipei County, Taiwan  
www.garmin.com  
Part Number 190-00585-00 Rev. A  
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