Table of Contents

SECTION ONE Introduction Glossary.1 Navigation Basics.4 SECTION TWO Getting Started Keypad Usage & Data Entry.5 Primary Pages.6 Power On & Marking a Position.8 Position Page and Map Pages.9 Going to a Waypoint.11 Compass Page & Cancelling A GOTO.12 Clearing the Map Display, Adjusting Contrast, & Power Off.13 SECTION THREE Reference Satellite Page.14 Backlighting.15 Position Page & User Selectable Fields.16 Marking a Position & Position Averaging Function.18, 19 Waypoint Pages & Managing Waypoints.19 TracBack Navigation.26 Creating and Using Routes.30 Using the Compass & Highway Pages.33 Map Page, Zooming, & Panning.37, 38 Map Page & Track Log Setup.39, 40 Menu Page & Distance/Sun Calculation.43 System Setup.46 Navigation Setup.47 Interface Setup & DGPS Interface.44, 45 Navigation Simulator.51 Appendix AInitialization.52 Appendix BInstallation.54 Appendix CSpecifications & Wiring.58 Appendix DMessages and Time Offsets.60 Appendix EMap Datums.62 Appendix FIndex.64

Glossary

The GPS 126/128 is a powerful navigation tool that can guide you anywhere in the world. To better understand its operation and capabilities, it may be helpful to review the basic terms and concepts briefly explained below. Other navigation and GPS definitions used in the manual are defined in the appropriate reference sections of the manual. Almanac Data Satellite constellation information (including location and health of satellites) that is transmitted to your receiver from every GPS satellite. Almanac data must be acquired before GPS navigation can begin. Bearing The compass direction from your position to a destination. Course Made Good (CMG) The bearing from the active from position (your starting point) to your present position. Crosstrack Error (XTK) The distance you are off a desired course in either direction. Desired Track (DTK) The compass course between the from and to waypoints. Differential GPS (DGPS) An extension of the GPS system that uses land-based radio beacons to transmit position corrections to GPS receivers. Estimated Time of Arrival (ETA) The time of day of your arrival at a destination. Estimated Time Enroute (ETE) The time left to your destination at your present speed.
Grid Coordinate system that projects the earth on a flat surface, using square zones for position measurements. UTM/UPS and Maidenhead formats are grid systems. Ground Speed The velocity you are traveling relative to a ground position. Latitude The north/south measurement of position perpendicular to the earths polar axis. Longitude An east/west measurement of position in relation to the Prime Meridian, an imaginary circle that passes through the north and south poles. Navigation The process of traveling from one place to another and knowing where you are in relation to your desired course. Position An exact, unique location based on a geographic coordinate system. Track (TRK) The direction of movement relative to a ground position. Universal Transverse Mercator (UTM) A grid coordinate system that projects global sections onto a flat surface to measure position in specific zones. Velocity Made Good (VMG) The speed you are traveling in the direction of the destination. Waypoint A specific location saved in the receivers memory.

Satellite Page The Satellite Page will allow you to monitor satellite signal reception and strength.
The graphic compass tape reflects your heading only while you are moving.

Position Page

Your track and speed are indicated immediately below. Underneath are two user-selectable fields for a variety of data. The current position is displayed in latitude and longitude or a user selectable grid format. A 12/24 hour clock is also provided.

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Map Page The Map Page acts as a window. It allows you to view your position, the path you have traveled over, and nearby waypoints. A diamond icon in the center of the screen represents your current position. As you move, you will see a thin line called a track log appear along the path you have just covered. Names of stored waypoints and waypoint symbols can also be shown on the map. The bottom corners of the screen always display your current track and speed. When going to a waypoint, highlighting an on-screen waypoint, or using the panning target crosshair, the corresponding distance and bearing are shown at the top corners of the screen. Navigation Page A navigation page gives you steering guidance when going to a waypoint. The GPS 126/128 has two navigation page choices: the Highway Page and the Compass Page. The Highway Page is the default and will be briefly explained here. The Compass Page is covered on page 36. The Highway Page uses a graphic highway to show your movement in relation to your desired course. The upper section shows bearing and distance to the waypoint and your current track and speed. The middle portion contains the actual highway. The highway indicates the crosstrack error, or distance and direction, your are off-course from your waypoint. Always turn in the direction the highway is pointing. For example, if the highway points straight up, no turn is needed. If the highway points right, you need to turn right until the highway points straight up. The pointer just below the CDI scale always points to your selected waypoint, relative to the direction you are moving. The remainder of the page contains two user-selectable fields. Menu Page The last primary page is the Menu Page. The Menu Page gives you access to the GPS 126/128s waypoint management, route, and setup features through a list of submenus. The Menu Page is covered on page 43.

Map Page The Map Page shows your progress on a moving track plotter and gives you a birds-eye-view of surrounding waypoints.
Highway Page With the Highway Page, you will get graphic steering guidance when navigating a route or going to a single waypoint.

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GETTING STARTED
Getting Started Tour Now that you are familiar with the primary pages, its time to take a tour. This is a live tour and is to be conducted with your unit installed and with the boat in the water. The tour will take you through the receivers basic features and functions as you move about on the water and assumes that the GPS 126/128 is turned on and initialized, (see page 52 for initialization procedure) and that you have not changed any of the factory settings (units of measure, selectable fields, etc.). If these settings have been changed, the pictures and descriptions in this manual may not match what you see on your screen. Navigation Simulator If you are not able to take the Getting Started Tour with your boat in the water, you may use the built-in navigation simulator to practice using the GPS 126/128. To use the simulator, see page 51. Marking a Position To begin the tour, lets take the position you have acquired (either by just initializing the unit or by having turned the unit on) and mark it as a waypoint for future reference.
1. Press the M key to capture and hold your position.
Power On & Marking a Position
The Welcome Page will be shown while the unit conducts a self test.
To mark a position, you must have obtained a 2D or 3D fix, or have the receiver in simulator mode. If you try to mark a position without a position fix, you will be alerted with a No GPS Position message.
Press the UP arrow to move forward through the alphabet or numbers and the DOWN arrow to move backward.
The mark position page will appear, showing the captured position and a default 3-digit waypoint name. Lets change the default name to something a little more meaningful, like DOCK.
2. Press the down arrow once to move the field highlight from the SAVE? field to the name field.

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3. Press F to clear the default waypoint name. 4. Press and hold theU key to scroll through the alphabet until the letter D appears. 5. Press the R key once to move the character highlight to the next character space. 6. Repeat steps 3 and 4 until the word DOCK is displayed. 7. Press F to complete entry of the name.

Position and Map Pages

Each waypoint may also be assigned a custom waypoint symbol for easy waypoint recognition on the map page.
1. Press F to activate the symbol menu. 2. Select the anchor symbol and press F. 3. Press the D key to highlight the DONE? field. 4. Press F to confirm the selected symbol. 5. With the SAVE? field highlighted, press F to confirm that you want to save the position as a waypoint named DOCK.
The arrow keypad is used for all data entry. Use the UP and DOWN keys to select letters, numbers, or menu options, and use the LEFT and RIGHT keys to move the cursor forward or backward along the line.
The mark position page will now be replaced by the Position Page (or whatever page was displayed prior to pressing the M key). The DOCK waypoint is now stored in the GPS 126/128s memory, and will remain there until you manually remove it or clear the receivers memory. For more on waypoint management, see pages 19-24. Using the Position and Map Pages Now that youve marked a position, lets see how the Position and Map Pages can be used to monitor your progress as you head out into the open water.
As always, ensure your primary focus is on boating traffic and monitor the GPS126/128 briefly when operating your boat.

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Using the Position and Map Pages (cont.) As you head out, the Position Page will help you monitor your movement.
Graphic Compass Tape Current Speed UserSelectable Field 12/24 Hour Time
Track Over Ground UserSelectable Field Position Display
The Map Page displays your present position as a diamond icon and provides a real-time graphic breadcrumb display of your track right on the screen.
The direction you are moving (your track) and your speed are displayed on the upper part of the page, just below the graphic compass tape. The latitude and longitude, along with two user-selectable displays, are continuously displayed in the middle of the page, and the time of day is displayed below. Now lets change the display to the Map Page and watch the track log of our tour:
1. Press the J key to change from the Position Page to the Map Page.
To view a larger area on the Map Page, lets change the zoom scale from.2 (default) to 1.0 nautical mile.
To select a larger zoom scale on the Map Page:
1. Press the H key until 1.0 n.m. zoom scale appears.
The moving maps default screen orientation is trackup. Track up means that your current direction of travel is always up (or towards the top of) the screen. It can also be set for north up, or desired trackup orientation through the map setup page.

To turn the GPS 126/128 off:
1. Press and hold the P key for 3 seconds.
Instantly change the screen contrast by pressing the arrow keypad while viewing the Satellite Page.

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Satellite Page
Status Field Horizontal Accuracy

Skyview Display

Signal Strength Indicators
The GPS 126/128s Satellite Page will help you determine which satellites are in view, and whether or not any satellites are being shaded or blocked. (See satellites 07 and 19 above). By periodically monitoring the signal strength bars at the bottom of the page and the north up sky view, you will be able to see how moving to another area with a clearer view of the sky will improve satellite reception and speed up signal acquisition.
The GPS 126/128s Satellite Page displays the status of various receiver functions. The status information will help you understand what the GPS 126/128 is doing at any given time, and will tell you whether or not the receiver has calculated a position fix.
Sky View and Signal Strength Bars The sky view and signal strength bars give you an indication of what satellites are visible to the receiver, whether or not they are being used to calculate a position fix, and the signal quality. The satellite sky view shows a birds-eye view of the position of each available satellite relative to the units last known position. The outer circle represents the horizon (north or track up); the inner circle 45 above the horizon; and the center point directly overhead. You can use the sky view to help determine if any satellites are being blocked, and whether you have a current position fix (indicated by a 2D NAV or 3D NAV in the status field). You can also set the sky view to a track-up configuration by changing the orientation option on the Map Page. (See pg. 41 for Map Setup instructions.) When the receiver is looking for a particular satellite, the corresponding signal strength bar will be blank and the sky view indicator will be highlighted. Once the receiver has found the satellite, a hollow signal strength bar will appear, indicating that the satellite has been found and the receiver is collecting data from it. The satellite number in the sky view will no longer appear highlighted. As soon as the GPS 126/128 has collected the necessary data to calculate a fix, the status field will indicate a 2D or 3D status.

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Receiver Status and EPE Receiver status is indicated at the top left of the page, with the current horizontal accuracy (EPE, estimated position error, in feet or meters) at the top right. The status will be shown as one of the following conditions: Searching the GPS 126/128 is looking for any available satellites in view. AutoLocate the GPS 126/128 is initializing and collecting new almanac data. This process can take 5 minutes, depending on the satellites currently in view. Acquiring the receiver is collecting data from available satellites, but has not collected enough data to calculate a 2D fix. 2D Navigation at least three satellites with good geometry have been locked onto and a 2dimensional position fix (latitude and longitude) is being calculated. 2D Diff will appear when you are receiving DGPS corrections in 2D mode. 3D Navigation at least four satellites with good geometry have been locked onto, and your position is now being calculated in latitude, longitude and altitude. 3D Diff will appear when you are receiving DGPS corrections in 3D mode. Poor GPS Coverage the receiver isnt tracking enough satellites for a 2D or 3D fix. Not Usable the receiver is unusable, possibly due to abnormal satellite conditions. Turn the unit off and back on to reset, and reinitialize the receiver if necessary. Simulator the receiver is in simulator mode. Screen Backlighting The GPS 126/128 feature illuminates the screen display for a user-defined interval (the default is 15 seconds). There are three stages of backlighting. When backlighting is on, a bulb icon will appear at the bottom left of the sky view. To adjust the duration of screen backlighting, refer to the system setup section (see page 47).
Note: A bulb icon will appear on the Satellite Page when backlighting is on.
Receiver Status & Screen Backlighting
The signal strength bars at the bottom of the page will not appear until the GPS 126/128 has found the satellites indicated at the bottom of the screen.
When backlighting is on, a bulb icon will appear on the Satellite Page. Use the icon to determine if backlighting is turned on during daylight hours.

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EZinit Prompt and Memory Erase
EZinit Option Prompt The Satellite Page also provides access to the EZinit prompt whenever a position fix has not been calculated. (The unit must be in searching, AutoLocate, acquiring, simulator, or poor coverage mode.) This allows you to reinitialize the unit (see Appendix A), and is useful if you have traveled over 500 miles with the receiver off and must initialize your new position. (The EZinit prompt will automatically appear if the receiver needs to be initialized. The prompt may also appear during normal use if the antenna is blocked from receiving satellite signals. Note: The GPS 126/128 features an internal lithium battery that will maintain the units memory when the receiver is not running. Memory Erase Function You may erase the GPS 126/128s memory in four quick steps. This will cause all stored data to be deleted, including routes, waypoints, and the track log.

The trip odometer, trip timer, and average speed fields are linked. Resetting one of these options in a user-selectable field will automatically reset the corresponding data in the other. This ensures that information shown in these fields reflects your current trip.
The user-selectable fields on the Position Page give you a variety of information to choose from.

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Altitude Field & Marking a Position
Altitude Field When the GPS 126/128 is acquiring satellites or navigating in the 2D mode, the last known altitude is used to compute your position. In cases where the GPS 126/128 has 2D coverage, entering your approximate altitude will enable the receiver to determine a 3D fix. Note: The altitude can not be changed when the GPS 126/128 has a 3D position fix.

To enter an altitude:

1. Ensure that ALT is displayed in the user-selectable field. 2. Highlight the ALT value field, and press F. 3. Enter a value, and press F.
Resetting the trip odometer will erase the previous mileage and set the odometer to 0.
Directly below the user-selectable fields is the Position field. The position field shows the current GPS position in latitude and longitude (default) or a user selectable position format (see navigation setup page 47). Directly below the position field is the time. Time can be displayed as a 12 or 24 hour clock (see system setup page 46).
Marking A Position The GPS 126/128 allows you to mark and store up to 500 positions as waypoints. A waypoint can be entered by taking an instant electronic fix, by manually entering coordinates (pg. 21), or using the bearing and distance to a known position (pg. 22).
To mark your present position:
1. Press M. The mark position page will appear, showing the captured position and a default threedigit name. 2. To save a default name and symbol, press F to confirm the Save? prompt. You may enter a known altitude to assist the GPS 126/128 in establishing a 3D fix.
To enter a different waypoint name:
1. Highlight the waypoint name field, and press F. 2. Make the appropriate changes, and press F. 3. Highlight SAVE?, and press F.
Note: To enter a different waypoint symbol or comment, see pg. 23.

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To add this waypoint to a route:
1. Highlight the Add to route number field, and press F. 2. Enter a route number, press F to confirm and press F again to save the waypoint.
Position Averaging & Waypoint Pages
Position Averaging Function The GPS 126/128 positioning averaging function will help reduce the effects of selective availability when marking a waypoint.
Note: As the GPS 126/128 calculates the FOM, it will rapidly change before it stabilizes on one number.
1. After you have pressed the M key, highlight the AVERAGE? field and press F. The Figure of Merit (FOM) field will display the value reflecting estimated accuracy of the averaged position. 2. The unit will continue averaging until you have highlighted SAVE? and pressed F. The GPS 126/128 will save new waypoints with a default three-digit name. To add the waypoint to a route, enter the desired route number, highlight SAVE?, and press ENTER.

To activate the GOTO function:
1. Press G. 2. Select the waypoint you want to navigate to, and press F.
Select a GOTO & MOB Function
Once a GOTO waypoint has been activated, the Compass Page or Highway Page will provide steering guidance to the destination until either the GOTO is cancelled or the unit has resumed navigating the active route (see pg 30).
1. Press the G key. 2. Highlight CANCEL GOTO?, and press F. Select a destination waypoint from the GOTO waypoint list.
Man Overboard Function The GPS 126/128s man overboard function (MOB) lets you simultaneously mark and set a course to a position for quick response to passing positions.
To activate the MOB mode:
1. Press the B key. 2. Press F to begin MOB navigation. The GPS126/128 will now guide you to the MOB waypoint until the MOB GOTO is cancelled. If you want to save the MOB waypoint be sure to rename it. The MOB function will overwrite any previous MOB waypoint when it is activated.
Once the MOB mode has been activated, steering guidance will be provided by the Compass or Highway Page. Activating another MOB will overwrite the previous MOB waypoint.

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TracBack
TracBack Navigation GARMINs patented TracBack feature allows you to quickly retrace your path using the track log automatically stored in the receiver. This feature eliminates the need to mark waypoints along the way and manually create and activate a route back to where you began your trip. Once a TracBack route is activated, it will lead you back to the oldest track log point stored in memory, so its usually a good idea to clear the existing track log at the start of each trip.
To clear the track log and define a starting point for a TracBack route:
1. From the Map Page, press F. 2. Highlight the TRACK SETUP option, and press F. 3. Highlight CLEAR LOG?, press F. 4. Highlight Yes?, and press F.
WARNING: Setting the track recording to OFF will disable the TracBack function.
To activate a TracBack route:
1. Press G, highlight TRACBACK?, and press F.
Once the TracBack function has been activated, the GPS 126/128 will take the track log currently stored in memory and divide it into segments called legs. Up to 30 temporary waypoints will be created to mark the most significant features of the track log in order to duplicate your exact path as closely as possible. These points will be indicated by waypoint numbers beginning with T on the waypoint list, and by a T symbol on the Map Page. The active route page will appear, showing a route from your present position to the oldest track log point in memory. Steering guidance to each waypoint will be provided back to the starting point of your track log. Note: You may delete a TracBack waypoint from a route, but only if the route is not active.

Waypoint 2

(active to waypoint)

Active Leg

Waypoint 1

(active from waypoint)

Routes are broken down and navigated in smaller segments called legs. The waypoint you are going to in a leg is called the active to waypoint and the waypoint immediately behind you is called the active from waypoint. The line between the active to and the active from waypoint is called the active leg. Whenever you activate a route, the GPS 126/128 will automatically select the route leg closest to your position as the active leg. As you pass each waypoint in the route, the receiver will automatically sequence and select the next waypoint as the active to waypoint.

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Route Definition Page

Comment Field

Route Number

Desired Track of Leg

Leg Distance

Copy Field

Total Distance

Function Prompts

The bottom of the route definition page features function fields which let you copy, clear, invert, or activate the displayed route. Routes 1-19 are used as storage routes, with route 0 always serving as the active route you are navigating. If you want to save a route thats currently in route 0, be sure to copy it to another open route or it will be overwritten by the next route activation. Routes can be copied, cleared, inverted, and activated through the route definition page.
To select the route definition page:
1. Highlight ROUTES from the Menu Page, and press F.
Routes enable you to store and use groups of frequently used waypoints together.
The route number field is displayed at the top of the page, with a 16-character user comment field to the right. If no user comment is entered, the field displays the first and last waypoint in the route. The waypoint list on the left side of the page accepts up to 30 waypoints for each route, with fields for desired track and distance between legs. The total route distance is indicated below the waypoint list.
Enter each waypoint in the order you would like to navigate the list. If you enter a waypoint not stored in memory, youll need to define the position on the waypoint definition page.

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Creating and Navigating Routes
To create a route from the route definition page:
1. Highlight the route number field, and press F. 2. Using the U or D key select an empty route number and press F. 3. Press F to begin entry of a route comment. 4. Enter your comment, and press the F key. 5. Press F to begin entering the first waypoint of your route. 6. Press F again to move to the next waypoint field. As you continue entering waypoints, the list will automatically scroll down.

Using Routes

You may use up to 16 characters to custom name a route. The default name will be the first and last waypoint in the route.

Note: A map scale represents the distance shown from the bottom to the top of the Map Page. For example, when viewing the 2 mile scale, the distance represented between the top and bottom of the screen is 2 miles.
The four corners of the Map Page are used to show your course and speed and the distance to either a cursor or to a destination waypoint.

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Zooming, Panning, and Pointing There are three main functions you can perform from the Map Page: zooming, panning, and pointing, Zooming is increasing or decreasing the display scale of the map. Panning is using a target crosshair and the arrow keypad to slide the map window in any direction, including diagonally, to view the surrounding area. Pointing is the act of highlighting a map position or waypoint on the map in order to create a new waypoint, review waypoint information, or GOTO a selected waypoint or map position. From the Map Page, you can also access the Map and Track Setup menus (see page 40).
To select a zoom scale (even while panning):
1. Press I or H once for each level of increase or decrease desired.
Zooming, Panning, & Pointing
A crosshair will appear when you activate the pan function. The distance and direction of the crosshair from your current position will be shown in the upper corners of the Map Page.
2. Press and hold down either key to increase or decrease by more than one scale.
To activate the pan function:
1. Press the arrow keypad in any direction.
As you begin to move the map, a crosshair will appear. This crosshair will now serve as a target marker for the moving map. The distance and bearing from your present position to the target crosshair will appear in the upper corners of the map. If you are conducting a GOTO at the time you activate the panning function, the crosshair bearing and distance will replace the bearing and distance of the GOTO waypoint. As you pan around the map, youll notice that the target crosshair will point to on-screen waypoints and highlight the waypoint name. Once a waypoint name is highlighted, you can review its waypoint definition page or execute a GOTO function right from the Map Page.

To select a submenu page from the Menu Page:
1. Highlight the page, and press F. 2. To return to the Menu Page, press Q.
Menu Page & Distance/Sun Calculation
Distance and Sun Calculations The distance and sun calculation page will give you the distance and bearing between any two waypoints or between your present position and a waypoint. It will also calculate the sunrise and sunset (in local time) for a particular date at either your present position or any stored waypoint.
To perform a distance and sun calculation:
1. Highlight the from field and press F. Enter the desired waypoint, and press F. 2. Highlight the to field and press F. Enter the destination waypoint, and press F. 3. The date field will become highlighted. Press F to enter the date youll arrive at your destination, and press F.
The Menu Page allows you access to a variety of waypoint, route, system and setup features.
If you havent marked your present position as a waypoint or you leave the to field blank, the sunrise and sunset at your present position will be shown. Message Page The message page is used to display all messages in the GPS 126/128. There are two types of messages: temporary alerts (e.g., approaching a waypoint) and condition alerts (e.g., WPT memory is full). All messages are indicated by a flashing on-screen box. After a temporary alert has been viewed, it is cleared. Condition alerts are displayed on the message page until the condition has been resolved.
To view the message page:
1. Highlight the MESSAGES field and press F. The GPS 126/128 will calculate the sunrise and sunset times of any stored waypoint or your present position. To calculate, enter the date and year and press ENTER.
See Appendix C for a complete list of messages.

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Interface Setup & DGPS
Interface Setup The GPS 126/128s interface page lets you specify the formats for connecting external devices. There are six options: GRMN/GRMN, None/None, RTCM/None, RTCM/NMEA, NMEA/NMEA, and None/NMEA. Each option lists the input format first, followed by the output format. To select I/O format:

Choose an interface option based upon what equipment you are using to transfer information.
Once the RTCM/NMEA option is selected, you can manually tune the beacon receiver from the frequency field.

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System Setup, Date/Time & Time Format
System Setup The system setup page is used to select the operating mode, time offset, and screen preferences. The GPS 126/128 has two operating modes: Normal Mode operates the unit using satellite tracking information. Simulator Mode allows you to operate the unit without acquiring satellites, and is ideal for practicing or entering waypoints and routes while at home.
To select an operating mode:
1. Highlight the mode field, and press F. 2. Select a mode, and press F.
The GPS 126/128s two operating modes are accessed through the system setup submenu.
Date and Time Setup The date and time is located directly below the mode field. Note: Date and time information is derived from the GPS satellites and cannot be changed by the user. Because the time shown is UTC time (Greenwich mean time), you will need to enter a time offset to display the correct local time for your area. To determine the time offset for your area, note your position and refer to the chart in Appendix D.
To enter the time offset:
1. Highlight the offset field, and press F. 2. Enter the time offset, and press F.
Note: Move the cursor to the left to change the plus or minus sign.
To display the correct local time, you must enter the appropriate offset from the chart at the end of Appendix C.
Time Format The time display shown on the system setup and Position Pages may be set to display the time in a 12- or 24-hour format.
To select the time format:
1. Highlight the hours field, and press F. 2. Select 12- or 24-hour display, and press F.

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Screen Contrast The GPS 126/128 has adjustable screen contrast controlled by an on-screen bar scale.
To set the screen contrast from the Menu Page:
1. Highlight the contrast field, and press F. 2. Adjust the bar scale to the desired contrast, and press F.
Screen Contrast & Backlighting
Note: The screen contrast can also be adjusted by pressing the rocker keypad while viewing the Satellite Page (see pg. 13).
Screen Backlighting Timer The screen backlight timer is adjustable for 15, 30, 60, 120, or 240 seconds. The timer also may be set to the Stay On setting for continuous use. Whenever backlighting is on, a bulb icon will appear on the Satellite Page.
To set the backlight timer:
1. Highlight the light field, and press F. 2. Select the desired setting, and press F. 3. To turn lighting on and off, press the P briefly. The Stay On setting will keep your backlighting on continuously.
Navigation Setup The navigation setup submenu page is used to select units of measurement for position formats, map datums, CDI scale, units, and heading information. Position Formats The default position format for the GPS 126/128 is latitude and longitude in degrees and minutes (hdddmm.mmm). You may also select degrees, minutes and seconds (hdddmmss.s); degrees only (hddd.ddddd); UTM/UPS coordinates; or British, German, Irish, Maidenhead, Swedish, Swiss, or Taiwan, or User grid formats.

To select a position format:
1. Highlight the position format field, and press F. Select the desired setting, and press F.
The position format may be set to display your choice of many formats. Note: degree and minutes is the default setting.

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Datums, CDI Settings, & Measurement
User Grid Option The user grid option lets you create a user-defined position format by establishing factors such as longitude of origin, scale, and false Easting or Northing. To define a user grid:
1. Select User Grid, and press F. Enter values for longitude origin, scale, false Easting and Northing, then press F. Highlight SAVE?, and press F.
Map Datums The datum field is located just below the position field and comes with a WGS 84 default setting. Although 106 total map datums are available for use (see Appendix D for map datums), you should only change the datum if you are using maps or charts that specify a different datum than WGS 84. To select a map datum:
The default map datum will cover worldwide navigation. However, if you are using a paper map or chart which uses a different map datum than WGS 84, then you may wish to switch to that datum. 1. Highlight the datum field, and press F. 2. Select the desired setting, and press F.

To define a user datum:

1. Highlight the datum field, and press F. 2. Scroll through the map datum options until User appears, and press F. 3. Enter values for DX, DY, DZ, DA, and DF using the rocker keypad, and press F. 4. Highlight SAVE?, and press F. The setup menu will reappear.
The user datum feature allows you to define the earth model used to calculate position coordinates. WARNING: Incorrect entries may result in substantial position errors.
CDI Scale Settings The course deviation indicator (CDI) field lets you select the +/- range of the CDI bar scale on the Highway Page. Three scales are available: +/- 0.25 (default), 1.25, and 5.0 miles or kilometers. Note: This CDI value represents the full deflection of scale to either side. To enter a CDI scale setting:
1. Highlight the cdi scale field, and press F. 2. Select the desired setting, and press F.
Units of Measure The GPS 126/128 lets you select statute (default), nautical, or metric units of measure for all speed and distance fields.

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To change the unit of measure:
1. Highlight the units field, and press F. 2. Select the desired unit of measure, and press F.
Speed Filter The speed filter allows you to determine how the GPS 126/128 responds to changes in track or ground speed. Three settings are available: automatic, on, or off. The Auto setting is the default and will monitor changes in your current track and speed and adjust the receivers response time automatically. The On setting allows you to manually enter a response time up to 300 seconds. Selecting a higher setting may be desirable in slow-speed applications with frequent changes in track.