Page 6

Acquiring Satellites
Acquiring Satellite Signals Because the GPS 45XL relies on satellite signals to provide you with navigation guidance, the receiver needs to have an unobstructed, clear view of the sky for best performance. What exactly does this mean? In a nutshell, the GPS receivers view of the sky will generally determine how fast you get a position fix, or if you get a fix at all. GPS signals are relatively weak and do not travel through rocks, buildings, people, metal, and materials such as thick canvas, so you need to make sure that youre not near any of these structures or materials when acquiring satellites. Once the GPS 45XL has calculated a position fix, youll usually have anywhere from four to eight satellites in view. The GPS 45XL will now continuously select the best satellites in view to update your position. If some of the satellites in view get blocked or shaded the receiver can simply use an alternate satellite to maintain the position fix. Although a GPS receiver needs four satellites to provide a 3D fix, the GPS 45XL can maintain a 2D fix with only three satellites. Before You Initialize Take the GPS 45XL outside and find a large, open area (try a nearby park) that has a clear view of the sky from horizon to horizon. Hold the receiver at a comfortable height, at arms length from your body, with the external antenna turned perpendicular to the ground.
GPS signals are blocked from reaching the receiver by buildings, rocks, metal structures, or materials such
as heavy canvas. Do your best to stay away from these structures and materials.

Welcome Page

Hold the receiver parallel to the ground and rotate the antenna perpendicular to the receiver.

To turn the GPS 45XL on:

1. Hold the unit so it is parallel to the ground and turn the external antenna perpendicular to the unit. 2. Press and hold B until the receiver turns on.
The welcome page will be displayed while the unit conducts a self test.

Page 7

Once testing is complete, the welcome page will be replaced by the status page, with the EZinit prompt ready for you to select one of two initialization methods: Select Countryallows you to initialize the receiver by selecting your present position from a list of countries in the GPS 45XLs internal database. This usually provides a position fix in 3-5 minutes. AutoLocateTM allows the GPS 45XL to initialize itself and calculate a position fix without knowing your present position. This usually provides a position fix in 7.5-15 minutes.

The satellite status 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 manually reinitialize the unit (see page 5-8 for instructions), and is useful if you have travelled over 500 miles with the receiver off and you know it must be initialized to your new position (the GPS 45XL will automatically offer the EZinit prompt after 10 minutes of unsuccessful satellite acquisition).

Page 19

Battery Level Indicator The satellite status page also features a battery level indicator, located below the status field to the left of the sky view, which provides a graphic display of the condition of the internal batteries.
! The battery level indicator is calibrated for alkaline batteries. Ni-Cad and lithium batteries will not accurately display the battery level due to voltage differences. No other receiver functions are affected by using Ni-Cad or lithium batteries.
Its always best to store your GPS receiver with the batteries installed to preserve the internal memory and data. The GPS 45XL features a rechargeable lithium battery that will maintain the internal memory for 3 months in the event that the batteries are removed or totally discharged.
Screen Backlighting The GPS 45XLs automatic backlight feature illuminates the screen display for a user-defined interval (the default is 15 seconds) after every keystroke. When backlighting is on, a bulb icon will appear at the bottom left of the sky view. To turn the screen backlighting on or off:
1. Press the B key. 2. To adjust the duration of screen backlighting, refer to the operation setup section (page 46).
A bulb icon will appear on the status page whenever the screen backlighting is on. The backlight will turn on for the time selected after every keystroke.
Using the screen backlighting can greatly affect battery life. If youre using your GPS 45XL primarily in daylight hours, you should keep the backlight timeout at the default 15 second setting.

Page 20

Position Page
Position Page The GPS 45XLs position page shows you where you are, what direction youre heading and how fast you are going (up to 99.9 mph), and is most useful when you are travelling without an active destination waypoint. A graphic compass tape at the top of the page displays your cardinal heading (while youre moving), with your current track and speed over the ground indicated below. The rest of the page shows your present position in three dimensions (latitude, longitude and altitude). The units of measure for speed, distance, position and altitude are all user-selectable through the navigation setup menu (see pages 47-48). The 12/24 hour clock and time offset options are available from the system setup menu (see page 46). Trip Odometer The position page also features a resettable trip odometer to measure the total distance travelled while navigating.

To reset the trip odometer:
1. Press the D key until the trip field is highlighted. 2. Press E, followed by L. 3. Press E to finish.
The speed displayed on the position page may fluctuate at slow speeds (or when youre standing still).
Altitude Display When the GPS 45XL is acquiring satellites or navigating in the 2D mode, the last known altitude will be used to compute your position. If the altitude shown is off by several hundred feet, you can manually enter your altitude for greater accuracy. Note that GPS altitudes can fluxuate due to errors.
1. Press the D key until the altitude field is highlighted.
To reset the trip odometer, highlight the trip field and press ENTER. Use the LEFT arrow key to clear the distance field and press ENTER to confirm.
2. Press E to begin entry of your altitude. 3. Use the U and D keys to enter a value in each character field, and use the L and R keys to move to the next character position. 4. Press the E key to confirm the altitude.

Page 21

Marking and Saving Waypoints Knowing your present position is only part of any navigation equation. You also need to keep track of where youve been and where you are going. Waypoints serve as electronic markers that let you keep track of starting points, destinations, navaids and any other important position. The GPS 45XL allows you to mark, store and use up to 250 waypoints. A waypoint position can be entered by taking an instant electronic fix or by manually entering a coordinate or range and bearing in reference to an existing waypoint. If you try to mark a waypoint without having a position fix, youll be notified with a No GPS Position message.
To mark your present position:
1. Press the M key to capture your position.
Marking & Storing Waypoints
The mark position page will appear, showing the captured position and a default 3-digit waypoint name.
To change the default position name :
1. Press the U key twice to move the field highlight from the save field to the name field. 2. Press E to begin entry of the name. Pressing the L key will clear any existing data. 3. Use the U and D keys to enter a value in the appropriate character field, and use the L and R keys to move to each character position. 4. Press E to confirm the waypoint name. The field highlight will move to the route field.

Page 23

Waypoint List Page The waypoint list page provides you with a complete list of all waypoints currently stored in the GPS 45XL. The total number of used and empty waypoints is indicated above the waypoint list. From the waypoint list page, you can retrieve a waypoint definition page, delete all userdefined waypoints, or GOTO a selected waypoint. If a waypoint is currently used in a route, the lowest route number will be indicated to the left of the waypoint name.
To review the waypoint definition page of a highlighted list waypoint:
To return to the waypoint list page (with the done field highlighted):

To GOTO a list waypoint:

1. Use the U and D keys to scroll through the list and select a waypoint. 2. To select a highlighted waypoint as a destination, press the G key. 3. Once the GOTOwaypoint page appears, press the E key to confirm the selected waypoint as your destination.
Waypoint List Page The total number of used and available waypoints is indicated at the top of the page. If a listed waypoint is a route waypoint, a RXX will be displayed (See RO2 above).
To delete all user-defined waypoints:
1. Use the U or D keys to move the cursor highlight to the delete all waypoints field. 2. Press the E key.
A warning page will appear, asking if you are sure you want to delete all user-defined waypoints and routes. If you want to continue and delete:
1. Press the L key to highlight the Yes field. 2. Press the E key. 3. Press the Q key to return to the menu page.
Deleting all user waypoints will also delete all routes stored in memory.
If you do not want to delete all waypoints:
1. Press E with the no field highlighted.

Page 24

Waypoint Definition Page The last of the three waypoint management pages is the waypoint definition page. This page lets you create new waypoints manually, or review and edit existing waypoints.
Waypoint Name Position Coordinates
Reference Waypoint Bearing from Reference Waypoint Function Prompts Waypoint Definition Page Use the waypoint definition page to review, rename or delete stored waypoints and to create new waypoints manually.
Distance from Reference Waypoint
To create a new waypoint manually, youll need to know its position coordinates or its distance and bearing from an existing waypoint.

Page 26

Editing Existing Waypoints The waypoint definition page also allows you to change the name, coordinates, comment or reference waypoint field for a stored waypoint.(Fields shown on page 24)
To edit the name, coordinates, comment, or reference waypoint field:
1. Use U and D to highlight the field you want to edit. 2. Press E to begin entry in the selected field. 3. Enter your new data. 4. Press the E key to confirm your changes.
Waypoint Comments Each waypoint stored in the GPS 45XL has a userdefined 16 character comment field. The default comment is the UTC date and time of the waypoints creation.
To change or add a comment:
1. Use the U and D keys to highlight the comment field. 2. Press E to begin entry of your comment. 3. Enter the comment and press the E key to confirm.
The waypoint comments field will automatically assign the date and time of creation to the waypoint comments field. You may enter a 16 character user comment at any time.
Renaming and Deleting Waypoints
To access the rename function from the waypoint definition page, highlight the RENAME?prompt and press ENTER.
The rename and delete function fields are located at the bottom left of the waypoint definition page (youll need to use the L key to move the field highlightout of its standard up-and-down scrollingsequence).

Page 27

To rename a stored waypoint:
1. Highlight the RENAME? field and press E. 2. Enter the new waypoint name and press E. 3. Press the E key to confirm your changes.
To delete a stored waypoint:
1. Highlight the DELETE? field and press E. 2. Press the L key to select the YES prompt. 3. Press E to delete the waypoint.
To delete a waypoint, confirm the Yes? prompt. Route or active waypoints may not be deleted until they are removed from the route or the GOTO has been cancelled.
Scanning Waypoints As you manually enter a waypoints name, the GPS 45XLs waypoint scanning feature will automatically display the first numerical or alphabetical match of the character you have entered to that point. This helps eliminate the need to always enter a waypoints complete name.
To scan waypoints from a waypoint field:
1. Highlight the waypoint name field and press E. 2. Press the L key to clear the name field. 3. Use the U and D keys to scroll through waypoints. 4. If you have more than one waypoint that begins with the same letter or number, you must use the R key to move to the next character positions as needed. Only the first character match is listed for each character set. 5. Once youve found the desired waypoint, press E.

To clear the track log and define a starting point for a TracBack route:
1. From the menu page, highlight the TRACKLOG option. 2. Press E to access the track log page. 3. Use the U key to highlight the CLEARLOG? option. 4. Press E. The clear log confirmation page will appear. 5. Use L to highlight the Yes? prompt and press E.
Clearing the log before you get started will define the position the TracBack function will return you to.

TracBack Navigation

To activate a TracBack route:
1. From the menu page, highlight the TRACKLOG option. 2. Press E to access the track log page. 3. Highlight the TRACBACK? option and press E.
Once the TracBack function has been activated, the GPS 45XL will take the track log currently stored in memory and divide it into segments called legs. Up to 30 temporary waypoints (e.g., T001) will be created to mark the most significant features of the track log in order to duplicate your exact path as closely as possible. A TracBack route from your present position to the oldest track log point will be created as the active route (the active route page will appear), and provide steering guidance to each waypoint back to the starting point of your track log.
Highlight the TracBack prompt and press ENTER to begin TracBack navigation. An on-screen status box will monitor the progress of the TracBack calculation.

Page 30

Tips on Creating and Using the TracBack Feature The GPS 45XLs TracBack feature is designed to help you quickly create and activate a route that follows your path back to a user-defined starting point. To get the most out of the TracBack feature, remember the following tips: Always clear your track log at the exact point that you want to go back to (trail head, truck, dock, etc.). The RECORD option on the track log setup page must be set to the Yes position. There must be at least two track log points stored in memory to create a TracBack route. If there are not enough available waypoints in memory to create a TracBack route, you will be alerted with a waypoint memory full message, and the receiver will use any available waypoints to create a TracBack route with an emphasis on the track log closest to the destination (the oldest track log point in memory). If the CRITERIA option on the track log setup page is set to a time interval, the TracBack route may not follow your exact path (keeping the criteria set to automatic will always provide the best TracBack route). If the receiver is turned off or you lose satellite coverage during your trip, the TracBack route will simply draw a straight line between any point where coverage was lost and where it resumed. If the changes of direction and distance of your track log are very complex, 30 waypoints may not be enough to accurately mark your exact path. The receiver will then assign the 30 waypoints to the most significant points of your track, and simplify segments with fewer changes in direction.

Bearing to Waypoint Track Over Ground Destination Waypoint Graphic Highway In this example, the highway page indicates that you are off course to the right. Steer left to get back on course. Notice the emphasis of the highway page is on the desired course. Estimated Time Enroute Velocity Made Good Pointer to Waypoint Distance to Waypoint Speed Over Ground
As you head toward your destination, the middle section of the screen provides visual guidance to your waypoint on a moving graphic highway. The moving arrow just below the course deviation scale always points to your selected waypoint relative to the direction you are moving. Your present position is represented by the diamond in the center of the course deviation scale. The line down the middle of the highway represents your desired track. As you navigate toward a waypoint, the highway will actually move, indicating the direction youre off course, relative to the position diamond on the CDI scale. To stay on course, simply steer toward the center of the highway.
If you get too far off course, a message box will appear to indicate what course to steer to get back on course most efficiently.
If you do get off the desired course by more than 1/5th of the selected CDI range, the exact distance you are off course will be displayed where the CDI scale setting normally appears (see the example at right). If you get too far off course (the highway has disappeared), a message box will appear to indicate what course to steer to get back on course.

Page 39

Using the Compass Page The GPS 45XLs compass page provides graphic steering guidance to a destination waypoint. The bearing (BRG) and distance (DST) to the waypoint are displayed at the top of the page, right below the destination waypoint field. The distance displayed is always the straight-line distance from your present position to the destination waypoint. The bearing indicates the exact compass heading from you to the destination.
Bearing to Waypoint Graphic Compass Pointer to Waypoint Track Over Ground Destination Waypoint Distance to Waypoint Speed Over Ground In this example, the compass page indicates that you are travelling in a northerly (351) direction and the destination waypoint is northwest (287) of your current direction of travel.

Page 41

Zooming and Panning There are three main functions you can perform from the map page zooming, pointing and panning. Each of these functions has its own field, which may be selected and activated for use. Whenever the map page first appears, the zoom field (at the top left) is always highlighted. The moving map has 12 map scales which are selected through the zoom function field.

To select a zoom scale:

1. Use the arrow keypad to highlight the zoom field. 2. Press the E key to begin range selection. 3. Use U or D to select a range scale and press E.
The second function field on the map page is the pan field, located at the top right of the screen. The pan function allows you to move the map with the four arrow keys to view areas outside the current map.
To activate the pan function:
1. From the zoom field, use R to highlight the pan field. 2. Press the E key to activate the pan function. 3. Use the arrow keys to move the map in any direction.
Selecting Map Scales To change the map scale, highlight the zoom field and press ENTER. Use the Up and DOWN keys to select the scale.
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 to destination will now be replaced by the distance and bearing from your present position to the target crosshair. As you pan around the map, youll notice that the target crosshair will snap 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 review the definition page for a waypoint highlighted in the map field:
1. Press E. Review and make any desired changes to the highlighted waypoint. To return to the map page, press E.
Panning Function During panning mode, an on-screen crosshair will appear. Your present position will remain as a diamond icon, with the range and bearing to the crosshair displayed in the top corners of the map.

Page 42

To GOTO a waypoint highlighted in the map field:
1. Press the G key. 2. Press the E key to confirm the GOTOwaypoint page.
To stop the panning function and display the present position diamond:

1. Press the Q key.

Pointing at On-Screen Waypoints The last field on the map page is the map itself. From the zoom or pan fields, the cursor highlight may be moved into the map display by pressing the down arrow key. The arrow keys will now move the field highlight through the map and point at on-screen waypoints.
To point at a displayed waypoint:
To stop panning, press the QUIT key.
1. Use the arrow keys to move the cursor highlight from the zoom field into the map field. 2. Once you are in the map field, use the four arrow keys to scroll through on-screen waypoints. The arrow key you use will determine the direction of your scroll. Once you have scrolled through all the waypoints, the cursor will move back to the zoom or pan function field.

To select a submenu page from the menu page:
1. Highlight the submenu page you want to view. 2. Press the E key to display the submenu page. 3. To return to the menu page, press the Q key.
Distance and Sun Calculation
Menu Page To select a submenu, use the UP and Down keys to highlight a menu option and press ENTER.
The distance and sun calculation page will give you the distance and bearing between any two waypoints and will calculate the sunrise and sunset (in local time) at a destination waypoint for a particular date.
To perform a distance and sun calculation:
1. Highlight the from field and enter the desired waypoint. Press E to move to the next field. 2. Highlight the to field and enter the destination waypoint. Press the E key to calculate the range and bearing to the destination waypoint. 3. Highlight the date field and enter the date for your destination. Press the E key to display the sun information.

Message Page

Distance/Sun Calculation The GPS 45XL 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.
The message page displays all current messages in the GPS 45XL. There are two types of messages: temporary alerts (eg., approaching a waypoint) and condition alerts (eg., battery power is low). All messages are initially 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 is resolved.
To view the message page:
1. Highlight the MESSAGES field and press E.
See appendix A for a complete list of messages.

Page 45

System Setup The first setup page is the system setup page, which is used to select the operating mode, time offset and screen preferences. The GPS 45XL has three operating modes: Normal Mode operates the unit at maximum performance, and provides a battery of life up to 12 hours on alkaline batteries. Battery Saver Mode is suitable for most applications, and extends battery life to up to 20 hours on alkaline batteries by reducing the receivers update rate when navigational conditions permit (e.g., youre travelling a steady course without constant speed or heading variations). Since battery saver mode changes the update rate based solely on navigational conditions, the battery life will vary accordingly. 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 E. 2. Use the arrow keypad to select a mode and press E.
System Setup Page Select battery saver mode to get the best possible battery life. Note that screen backlighting will always have the biggest effect on battery life, regardless of operating mode.

To clear the track log:

1. Highlight CLEARLOG? and press E. 2. A warning page will appear, and ask you to confirm your actions. Use the L key to move the field highlight to the Yes? field and press E.
To clear the track log, confirm the Yes? prompt.
TracBack Function The TracBack option lets you activate a TracBack route using the track log (see pages 29-30 for more information).
1. Highlight the TRACBACK? option and press E.

Page 51

Interface Setup The interface setup page lets you specify the interfacing formats for connecting external devices. There are five interface options: GRMN/GRMN, None/None, None/NMEA, RTCM/None, and RTCM/NMEA. Each option lists the input format first, followed by the output format.

To select I/O format:

1. Highlight the I/O field and press E. 2. Use the U and D keys to toggle through and select the desired setting, and press E.

Interface Setup

The GRMN/GRMN setting is a proprietary format that lets you exchange information such as waypoints, routes and track logs between two GARMIN GPS devices or a PC. During data transfer, the number of packets being exchanged will be displayed on screen.
To select a transfer option:
1. Highlight the host field and press E. 2. Use U and D to select a setting and press E.
Interface Setup Page The default interface setting is the GARMIN/GARMIN option, which can be used for unit-to-unit data transfer or interfacing with a GARMINPCKit.
To disable all interfacing capabilities, select the None/None setting. If you want to output NMEA data to compatible external devices without any differential input capability, select the None/NMEA setting. Once a NMEA output setting has been selected (with or without RTCM input), the NMEA field will become highlighted. NMEA formats 0180, 0182 or 0183 (1.5 or 2.0) are available.

To select a NMEA format:

1. Press E to begin a NMEA selection. 2. Use U and D to select a format, and press E.
DGPS Interface The last two format settings allow the differential-ready GPS 45XL to accept RTCM DGPS corrections in RTCM 104 version 2.0 format. Using DGPS corrections will improve receiver accuracy to 5-10 meters, regardless of errors induced by the governments Selective Availability (SA) program. The RTCM/NONE format will allow connection to any manually tuned beacon receiver by using the proper output interface. The baud rate is selectable from the GPS 45XL.
NMEAInterface Once a NMEA format is selected, the baud rate will automatically be set to the proper speed. See Appendix C for a list of NMEA sentences.

Page 52

DGPS Interface (continued) The RTCM/NMEA selection controls the GARMIN GBR21 differential beacon receiver. Once a RTCM setting has been selected, the GPS 45XL will either automatically try to tune the last frequency and bit rate you selected or will switch to the default frequency of 304.0 kHz with a bit rate of 100 bps if no previous beacon has been tuned. You may also enter your own frequency and bit rate if desired.

Simulator Mode

Once the simulator mode has been activated, use the position, compass or highway page to set your speed and track. You may also enter a new position if you desire (only from the position page).
To enter track, speed and position:
1. Highlight the TRACK field and press the E key. 2. Enter a track heading and press E. 3. Highlight the SPEED field and press E. 4. Enter a speed and press E. 5. Highlight the POSITION field (position page only) and press E. 6. Enter a position and press the E key.
Speed, Track & Position Once simulator mode is selected, speed and track values may be entered on the position or navigation pages. A simulated position may also be entered on the position page.
The GPS 45XL does not track satellites in simulator mode. Although you can create and save waypoints and routes while using the simulator mode, never attempt to use the simulator mode for actual navigation.

Page 54

Appendix A Introduction
Messages & Preface Time Offsets
The GPS 45XL uses a flashing on-screen message indicator to alert you to important information. Whenever the message indicator appears, press PAGE to view the message page. There are two types of messages: temporary alerts and condition alerts. Temporary alerts are cleared from the message page after viewing, while condition alerts remain until the condition has been resolved. Pay careful attention to all messages for your own safety.
Active WPT Cant be DeletedYou have attempted to change the active to or active from waypoint. Clear the active route or GOTO before making your changes. Accuracy has been DegradedThe accuracy of the GPS 45XL has been degraded beyond 500 meters due to poor satellite geometry or data quality. You should check other navigational sources to verify the position indicated. Already ExistsThe name you are entering already exists in the GPS 45XLs memory. ApproachingYou are one minute away from reaching a destination waypoint. Battery Power is LowThebatteries are low and should be replaced. No DGPSPositionNot enough data is available to compute a DGPS position. No RTCM InputBeacon receiver is improperly connected or baud rates do not match. Poor GPSCoverageThe GPS 45XL cannot acquire the necessary number of satellites to compute a position. Try another location with a clearer view of the sky. Power Down and Re-initThe GPS45XL is not able to calculate a position due to abnormal satellite conditions. Turn the unit off and verify the last position shown by other means. Try the unit again later, possibly in a different location. Read Only Mem has FailedThe permanent memory has failed and the unit is not operable. Take your unit to an authorized GARMIN dealer for repairs. Received an Invalid WPTA waypoint was received during upload transfer that has an invalid identifier. Receiver has FailedA failure in receiver hardware has been detected. If this message persists, do not use the unit and take it to an authorized dealer for repair. Route is FullYou have attempted to add more than 30 waypoints to a route. Route is not EmptyYou have attempted to copy into a route already in use. Route Waypoint Cant be DeletedThe waypoint you are trying to delete is part of a route. Delete the waypoint from the route before removing it from memory. Route Waypoint was DeletedA route waypoint entered does not exist in the database and has been deleted from the route. RTCM Input has FailedDGPS data being received has been lost. You are no longer receiving the beacon signal. Searching the SkyThe GPS 45XL is in searching the sky for almanac data or the unit is in AutoLocateTM mode.

Map Datums

Prov S Chln 63 Puerto Rico Qatar National Qornoq Reunion Rome 1940 RT 90 Santo (Dos) Sao Braz Sapper Hill 43 Schwarzeck Sth Amrcn 69
South Asia SE Base SW Base
Timbalai 1948 Tokyo Tristan Ast 68 Viti Levu 1916 Wake-Eniwetok WGS 72 WGS 84 Zanderij
Prov So Chilean 63- S. Chile Puerto Rico & Virgin Islands Qatar National- Qatar Qornoq- South Greenland Reunion- Mascarene Island Rome 1940- Sardinia Island Sweden Santo (Dos)- Espirito Santo Island Sao Braz- Sao Miguel, Santa Maria Islands (Azores) Sapper Hill 1943- East Falkland Island Schwarzeck- Namibia South American 69Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay, Peru, Venezuela, Trinidad and Tobago South Asia- Singapore Southeast Base- Porto Santo and Madiera Islands Southwest Base- Faial, Graciosa, Pico, Sao Jorge and Terceira Islands (Azores) Timbalai 1948- Brunei and E. Malaysia (Sarawak and Sabah) Tokyo- Japan, Korea, Okinawa Tristan Astro 1968- Tristan da Cunha Viti Levu 1916- Viti Levu/ Fiji Islands Wake-Eniwetok- Marshall Isl. World Geodetic System 1972 World Geodetic System 1984 Zanderij- Surinam

Page 58

Appendix C Introduction
Specifications Preface & Wiring
The GPS 45XL is constructed of high quality materials and should not require user maintenance. Should your unit ever need repair, please take it to an authorized GARMIN service center. The GPS45XL has no user-serviceable parts. Never attempt any repairs yourself. To protect your GPS 45XL, keep it in its carrying case when not in use, and never allow gasoline or other solvents to come into contact with the case. Clean the case and lens with a soft cloth and a household window cleaner. Case: Size: Weight: Waterproof, dry nitrogen-filled 6.15H x 2W x 1.23D (15.6 x 5.1 x 1.23 cm) Approx 9.5 ounces (269g) w/ batteries 5 to 158F (-15 to 70C)

PHYSICAL

Temperature Range: PERFORMANCE Receiver:
Differential-ready MultiTrac8 Approx. 20 seconds (warm start) Approx. 2 minutes (cold start) Approx. 7.5 minutes (AutoLocateTM)

Acquisition Time:

Update Rate: Position Accuracy: Velocity Accuracy:
1/second, continuous 5-10 meters (16-33 ft.) with DGPS corrections* 15 meters (49 ft.) RMS** 0.1 knot RMS steady state (90 knots/103 mph max.)

Investigation of the accuracy of hand held GPS for desert locust control operations Introduction The use of hand held GPS has become increasingly common in desert locust control and survey organisations over recent years. They are now considered an indispensable tool in any locust control organisation. Their primary use has been, and remains, the accurate location of locusts in the field this data is reported back to HQ and allows plotting of the positions of populations with some accuracy. The use of GPS is important in the development of GIS systems, as the data can be fed into the system and be accurately pinpointed on digital maps. However, GPS also has some role in control operations. Again, areas to be sprayed are recorded by GPS and the position data passed to the control teams (either ground or aerial) and the teams can find their way to the correct site. GPS has also been recommended as a way of deliminating blocks for spraying. By recording the corners of the blocks, it is thought that accurate data is obtained which allows precise spraying. While undoubtedly better than nothing, the inherent inaccuracy of GPS (which is due to selective degradation and atmospheric conditions) may give data with less accuracy than claimed by the users. Recent trials in the use of aerial DGPS relied to some extent on hand held units plotting the positions of areas to be sprayed or to be avoided. The authors of this showed that although the DGPS was accurate enough to accurately fly the correct paths, the inaccuracy of the hand held system compromised the overall accuracy of the system. The work reported in this technical note has a number of objectives. 1) 2) 3) 4) To examine the accuracy of the hand held GPS systems. To examine how accurate GPS is at recording a track. To examine the use of GPS, and its errors, in block delimination. To develop methods for use in ground DGPS trials.
Methods The GPS units used in this study were Garmin GPS 45XL units. Two units were used. Data was recorded on the unit using the internal memory, then later downloaded to computer using the Garmin PCX5 software supplied by the manufacturer. The data were downloaded either into a laptop computer (Toshiba 2110) or onto a desktop. Analysis was undertaken using the PCX5 software to measure distances and bearing. The test methods used were based on those published by for the determination of the accuracy of ground based DGPS systems, with modifications based on the differing nature of the systems. Due to the lack of precise maps for the region, the accuracy of the hand held units was determined by self reference, rather than to an absolute reference. In all tests, the units were allowed to warm up for 30 minutes prior to data logging. Prior to the work commencing the units were run for 2 hours to initiate and update the almanacs.

Test 1

Static stability Static stability and accuracy are defined as the ability of the unit to find a position and reproduce it over a period of time. Test 1A and 1B. After the 30 minute warm-up period, the units were left with the aerials 2 m apart and data on position was logged every 15 seconds (Test 1A) or every 5 minutes (Test 1B). Test 2 The ability to record a straight line track of known direction and length. A 500 m section of straight road was chosen for this test. The road had concrete posts on one side at 15 m intervals, which were determined to be in a straight line by observation. The orientation of the posts was determined using an accurate sighting compass. After a warm up of 30 minutes, the units were positioned in a car with the external aerials 2 m apart mounted on the roof top. The units were set to record for 10 minutes, at 15 second intervals at the start of the run. The car was then driven in a straight line close to the posts at 5 km/hr, with the units recording position at 5 second intervals. At the end of the run, the units recorded the position for 10 minutes. The runs were repeated 3 times in each direction.

Test 3 Marking a target. A plot of exactly 50 m x 50 m was marked out in open desert. Only one unit was used for this trial, using the integral aerial of the unit (Unit GPS Unit 2). At each corner of the plot, the unit recorded the position. This was repeated twice for each corner.
Results Note that the results are presented graphically, and there may be some distortion due to transforming the data. The error distances are noted under each figure. Only example data is presented. Test 1. Static Stability

STA 1 DATA

18.0881

18.088

Latitude

18.0879

18.0878

18.0877

18.0876 -16.0166

-16.0165

-16.0164

-16.0163

-16.0162

-16.0161

-16.016

Longitude

Static Position Unit 1 Max N-S Distance 84 m Max E-W Distance 119 m

STA 2 DATA

18.0882

18.0878 -16.0167

-16.0166
Static position Unit 2 Max N-S Distance - 64 m Max E-W Distance 79 m

Run Unit 1

18.089

18.087

18.086

18.085

18.084

18.083 -16.0165

-16.0159

-16.0158

-16.0157

Lontitude

Measuring a straight line run Actual Distance 500 m Measured GPS Distance 838 m Actual Bearing 021 Magnetic GPS Bearing 352.8 Stationary Position Run Mean NS Range (m) 83.7 152.3 64.8 73.5 93.58 EW Range (m) 119.8 131.8 79.1 95.5 106.55

Plot Corner Marking

17.58 17.5799 17.5798 17.5797 17.5796 17.5795
17.5794 17.5793 17.5792 17.5791 17.579 17.5789 17.5788 17.5787 17.5786 17.5785 -15.5875 -15.5874 -15.5873 -15.5872 -15.5871 -15.587 -15.5869 -15.5868
Plot Corners as Marked by GPS
Discussion The nature of this study meant that there was no absolute reference to measure the accuracy of the GPS units. Therefore, instead of talking of error, the term range is used to describe the accuracy of the GPS units. It is clear from the static tests that the range of positions given by the units is in line with the selective degradation of the signal (ie in a stationary position, the unit can locate itself within a square approximately 100 m x 100 m) although of course, in this test there is no way of knowing the real position. For the marking of a straight line, the line was reasonably straight, but instead of recording the distance travelled as 500 m, the distance was given as over 800 m. This is slightly greater than the range of 100 m of position would lead one to expect, but the inaccuracy of this measurement is compounded by inaccuracy in measuring the distance using the vehicle odometer. What is surprising from this result is that the bearing calculated by the GPS unit (at 352) is very different from the compass measured bearing of 021 magnetic. Even allowing for variation (9W) which was autoset on the GPS unit, the bearing difference is over 20. The plot corner marking was subject to great inaccuracy. Even ignoring the true position, neither test (on a perfectly marked square) gave a good representation of the corners of the plot. Use of Hand held GPS for Locust Control Spraying Operations The use of GPS in spraying operations, based on the data generated above, is not suitable for anything other than a relatively general indication of the position of the target. The failure of the unit to provide a reasonable approximation of a square target makes its use for delimiting

a locust target of little value. The errors associated with the inaccuracies of plot corner marking are shown in the graph below:
Effect of GPS Position Errors on Plot Size Estimation
40 m 80 m 20 m 100 m 60 m

% Plot Overestimation

Plot Size
It can be seen from this graph that at a error of 100 m, the plot size must be a minimum of 1050 m x 1050 m - ie 110 ha before the error associated with the inaccuracy of the GPS unit is less than 20 %. Obviously, if the GPS error is smaller, then the plot size to maintain an error of less than 20% also decreases at 20 m error, the plot needs to be a minimum of 250 m x 250 m ie 6.25 ha. This analysis is somewhat simplified, as it assumes all errors exaggerate the plot size of course it is equally probable that the error in the GPS data could underestimate the plot size, in which case the infested area would not be covered. It is also equally true that the position given will lie anywhere within the radius of the GPS range. Careful consideration therefore needs to be given in how GPS units are used in desert locust control. The perceived accuracy of the units may in fact lead to significant errors; the problem is in knowing how accurate the unit is at any one time. This problem was highlighted in the trials undertaken by the project on aerial DGPS. Although DGPS is known to be accurate to within a few metres, this accuracy is of little use if the basis on which it is used is based on much less accurate GPS data. In the aerial trials, an exclusion block was marked with hand held GPS units, but when flown with DGPS, clearly showed up the error. There may therefore be a false confidence in marking environmentally sensitive areas (ESA) with hand held GPS, and then spraying with DGPS, unless the error associated with hand held GPS is allowed for ( ie marked position plus 100 m further away from the ESA). Further Work Further work on hand held GPS units will continue as time permits; this will be aimed at improving the accuracy of the units for target delimitation, possibly through the use of low cost Differential GPS receivers, or combining data from more than one unit.
Recording, downloading and managing data is also an area than needs further development particularly systems that can be easily used by the CLAA in routine desert locust operations. Further work is planned on the use of DGPS for spraying, and ideas and techniques developed in this current preliminary study will aid in these trials. Dr R. Aston CTA, GCP/INT/651/NOR 12th October 1999