Garmin GPS 3 Manual

							Alarms Settings
Clock Alarmuses the internal clock to provide an ‘Alarm Clock’ message at the time 
you set.
To enable/disable the alarm clock:
1. Highlight the ‘Clock Alarm’ field and press ENTER.
2. Select ‘On’ or ‘Off’ (as desired) and press ENTER.
3. If enabling the alarm, highlight the time field (to the immediate right) and press ENTER. Enter the
alarm time using the rocker keypad and press ENTER.
NOTE: The GPS III must be turned on when the alarm time is reached. Otherwise, the
message will not occur.
Arrival Alarmprovides an alarm message once you’re within a set distance from your
destination waypoint. As you approach the destination waypoint, an ‘Arrival at ____’ 
message occurs when you are within the alarm distance you entered.
Off Course Alarmprovides an alarm message (‘Off Course Alarm’) when you deviate off
course beyond the specified limits. 
To set the arrival and/or off course alarms:
1. Highlight the ‘Arrival Alarm’ or ‘Off Course Alarm’ field and press ENTER.
2. Select ‘On’ or ‘Off’ (as desired) and press ENTER.
3. If enabling the alarm, highlight the alarm distance field (to the immediate right) and press ENTER.
Enter the alarm distance using the rocker keypad and press ENTER.
An ‘Approaching’ message
automatically appears one
minute before reaching the
destination waypoint. The
arrival alarm allows you to set
a distance-defined message.
The ‘Off Course Alarm’ pro-
vides an alert if you drift off
course beyond the limits you
have set.
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REFERENCE
Setup Menu: Alarms
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							Position Settings
Position Formatis used to change the coordinate system in which a given position
reading is displayed. The default format is latitude and longitude in degrees and minutes
(hddd°mm.mmm’). The following additional formats are available:
• hddd.ddddd° — latitude/longitude in decimal degrees only
• hddd°mm’ss.s” — latitude/longitude in degrees, minutes, seconds
• UTM/UPS — Universal Transverse Mercator / Universal Polar Stereographic grids
• British Grid • German Grid
• Irish Grid • Swedish Grid
• Swiss Grid • Taiwan Grid
• Maidenhead
Map Datumallows you to select the datum reference used to determine where a given
position is. The default setting is ‘WGS 84’. Although over 100 datums are available (as
listed on page 82), you should only change the datum if you are using a map or chart
that specifies a different datum. If no datum is specified, you may select each datum
applicable to your region until you find the datum that provides the best positioning at a
known point.
WARNING: Selecting the wrong map datum can result in substantial position errors.
When in doubt, use the default WGS 84 datum for best overall performance.
To change the position format and/or map datum:
1. Highlight the ‘Position Format’ or ‘Map Datum’ field and press ENTER.
2. Select the desired setting (using the rocker keypad) and press ENTER.
Only the latitude/longitude,
UTM/UPS and Maidenhead
settings apply worldwide. The
additional grid settings are
only valid for a specific region.
Over 100 different datums
are provided to allow the GPS
III to correspond to various
paper charts/maps. Use WGS
84 unless your chart specifies
otherwise.
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REFERENCE
Setup Menu: Position
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							Interface Settings
Formatlets you control the input/output format used when connecting your GPS III to
external NMEA devices, a DGPS beacon receiver, a personal computer, etc. Five format
settings are available:
• GARMIN — the proprietary format used to exchange waypoint, route, track log
data with a PC or with another GPS III.
• NMEA — supports the input/output of standard NMEA 0183 version 2.0 data.
• None — provides no interfacing capabilities.
• RTCM/NMEA — allows Differential GPS (DGPS) input using a standard RTCM
format and also provides NMEA 0183 version 2.0 output.
• RTCM In — allows DGPS input using a standard RTCM format, without any
output capabilities.
To select an input/output format:
1. Highlight the ‘Format’ field and press ENTER.
2. Select the desired setting and press ENTER.
3. If the ‘GARMIN’ format is selected, highlight the ‘Transfer Mode’ field and press ENTER. Select
the desired setting and press ENTER. The ‘Transfer Mode’ field allows you to specify what infor-
mation to request or send to a second GPS III. The ‘Host’ setting lets you control all data transfer
functions from the second GPS III or from a PC.
4. If an ‘RTCM’ format is selected, additional fields are provided to control a GARMIN GBR 21 bea-
con receiver directly from your GPS III. You can enter the beacon frequency and bit rate on the
GPS III and the information will be used to tune the beacon receiver. For more information, refer
to the owner’s manual for the GBR 21.
The ‘GARMIN’ option allows
the GPS III to exchange data
with a PC or another GPS III.
Use this setting with the
optional PC Software Kit.
Select the ‘RTCM/NMEA’
option to use the GPS III
along with a GBR 21
Differential Beacon Receiver.
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REFERENCE
Setup Menu: Interface
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							The GPS III can be mounted on the dashboard of an automobile or to another
convenient surface using the two Velcro™ strips provided with the unit. 
To mount the GPS III using the Velcro strips:
1. Select a location for the unit that pro-
vides a clear and unobstructed view of
the sky.
2. Remove the paper strip liners from both
pieces of Velcro.
3. Make sure the surface to which you’re
adhering the Velcro is clean and dry.
Place the adhesive side of the rough
piece of Velcro on the desired mounting
surface, and press into place. 
4. Place the adhesive side of the smooth
piece of Velcro on the bottom of the unit (between the rubber anti-skid bumps), and press into place.
5. Mount the unit, placing one piece of Velcro on top of the other.
Optional Dash Mounting Bracket
An optional dash mount bracket is also available for your GPS III. This
bracket allows you to adjust the GPS III for best viewing angle, while installed
on the dash of a vehicle. The dash mount bracket may be permanently
installed or temporarily mounted using supplied Velcro fasteners.
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APPENDIX A
Dashboard Mounting
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							The GPS III is constructed of high-quality materials and should not require
user maintenance. If your unit ever needs repair, please take it to an authorized
GARMIN service center. The GPS III has no user-serviceable parts. Never attempt
any repairs yourself. To protect your GPS III, keep it in its carrying case (optional accessory) when not in use, and
never allow gasoline or other solvents to come into contact with the case. To clean the case and lens, use a soft cloth
and a household window cleaner.
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APPENDIX B
Specifications
PHYSICAL
Case: Fully-gasketed, high-impact plastic alloy, 
waterproof to IPX7 standards
Size:6.15”H x 2”W x 1.23”D (15.6 x 5.1 x 1.23 cm)
Weight:Approx. 9 ounces (255g) w/ batteries
Temperature Range:5 to 158ºF (-15º to 70ºC)†
Memory Back Up:Internal Lithium Battery
PERFORMANCE
Receiver:Differential-ready PhaseTrac12™ 
Acquisition Time:Approx. 15 seconds (warm start)
Approx. 45 seconds (EZinit/cold start)
Approx. 5 minutes (AutoLocate™)
Update Rate:1/second, continuousPosition Accuracy:1-5 meters (3-15 ft) with DGPS
corrections*
15 meters (49 ft) RMS**
Velocity Accuracy:0.1 knot RMS steady state
Dynamics:Performs to specification to 6 g’s
Interfaces:NMEA 183, RTCM (for DGPS corrections) and
RS-232 for PC interface
Antenna:Detachable with standard BNC connector
POWER
Input:Four 1.5-volt AA batteries† or 10-32 VDC external
Power Consumption:0.75 watts max.
Battery Life:Up to 8 hours ‡
Specifications subject to change without notice.
* With optional GARMIN GBR 21 Beacon Receiver Input.
** Subject to accuracy degradation to 100m 2DRMS under the U.S. DoD-imposed Selective Availability Program.
† The temperature rating for the GPS III may exceed the usable range of some batteries. Alkaline batteries can rupture at high temperatures.
‡ Alkaline batteries lose a significant amount of their capacity as temperature decreases. Use lithium batteries when operating the GPS III in
below freezing conditions. Extensive use of screen backlighting will significantly reduce battery life.
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							Interfacing formats are selected from the Setup Menu, described on page 67. The
input/output lines on your GPS III are RS-232 compatible allowing easy
interface to a wide range of external devices, including PCs, differential
beacon receivers, marine autopilots and/or a second GPS receiver.
The NMEA 0183 version 2.0 interface format is supported by the
GPS III and enables the unit to drive up to three NMEA devices:
NMEA 0183 version 2.0 Approved sentences:
GPGGA, GPGLL, GPGSA, GPGSV, GPRMB, GPRMC, GPRTE,
GPWPL, GPBOD
Proprietary sentences:
PGRME (estimated error), PGRMM (map datum), PGRMZ
(altitude), PSLIB (beacon receiver control)
DGPS (Differential GPS) corrections are accepted in RTCM SC-104
version 2.0 format through the Data In line. The GARMIN GBR 21 is
the recommended beacon receiver for use with the GPS III. Other beacon
receivers with the correct RTCM format may be used, but may not correct-
ly display status or allow tuning control from the GPS unit.
The GPS III may be hard-wired to a vehicle’s electrical system (10-32
VDC) using an optional power/data cable. Consult the wiring diagram to the
right for proper connections. (The male connector on the back of the GPS
III is illustrated.) A cigarette lighter adapter is also available to power your
GPS III without making permanent connections.
Additional cables are available to connect your GPS III to a PC-compat-
ible computer’s serial port (PC Interface Cable) or to connect to a second
GPS III (Data Cross-Load Cable). Contact your GARMIN dealer for any of
these accessories.
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APPENDIX C
Wiring / Interfacing
GARMIN
GBR 21
(+)Power
(-)Ground
Data In Data Out
GPS III Connections (from back of unit)
GARMIN GBR 21 Beacon Receiver
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							The GPS III’s antenna may be removed to allow attachment of an optional
remote-mounted antenna. In some applications, using a remote-mounted antenna
will dramatically increase the number of satellites received. The GPS antenna should
be mounted in a location which provides an unobstructed view of much of the sky. A minimum of four satellites are
needed to determine a three dimensional position. Satellite coverage will vary throughout the day, but may be checked
at any time using the Satellite Status Page (see page 25). If satellite reception is limited in your particular installation,
you may want to consider one of the following options:
Remote Suction Cup Mount– allows you to mount the standard detachable antenna up to 6 feet away from the 
GPS III unit, using a suction cup mount. This mount should only be used inside a vehicle.
GA 26 Remote Antenna– allows you to mount an amplified antenna outside the vehicle, up to 8 feet away, using 
supplied magnetic or suction cup mounts. Trunk lip and permanent flange mounts are also available.
GA 28 Remote Marine Antenna- allows you to mount an amplified antenna outside the vehicle, up to 30 feet 
away, using a standard 1-inch marine antenna mount (not supplied). An optional extension cable allows you to 
mount the antenna up to 60 feet away.
To remove the attached antenna:
1. Rotate the antenna toward the rear of the unit as shown. 
Note: The antenna can only be removed or installed 
in this position.
2. Pull the antenna gently away from the unit.
3. To install an optional external antenna, mate the 
BNC connector notches with the mounting posts 
and turn the knurled knob one-quarter turn clockwise.
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APPENDIX D
Antenna / Remote Mounting
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							Alarm Clock—The alarm clock time that was set from
the Alarms submenu has been reached.
Approaching—You are one minute away from reaching
a destination waypoint.
Arrival at—You have reached your destination way-
point.
Battery Power Low—The batteries are low and should
be replaced.
Data Transfer Complete—The unit has finished
uploading or downloading information to the connected
device.
Degraded Accuracy—The unit’s accuracy has been
degraded beyond 500 meters due to poor satellite geom-
etry or data quality. Check other navigational sources to
verify the position indicated.
Leg not Smoothed—The upcoming route leg is too
short for smooth waypoint transitions.
Memory Battery Power Low—The battery that sus-
tains user memory is low and should be replaced by an
authorized service center as soon as possible. Failure to
do so may result in loss of stored data, including all
user waypoints and routes.Need Altitude for 2D Nav—The unit needs altitude
input in order to start and/or continue 2D navigation.
Need to Select Init Method—You must select an ini-
tialization method so the unit can locate satellites and
obtain a fix.
No Differential GPS Position—Not enough data is
available to compute a DGPS position.
No RTCM Input—Beacon receiver is improperly con-
nected or baud rates do not match.
Off Course Alarm—You are left or right of course,
beyond the limits set on the Alarms submenu.
Oscillator Needs Adjustment—The GPS III has detect-
ed excessive drift in its internal crystal oscillator which
may result in longer acquisition time. The unit should be
taken to an authorized GARMIN service center.
Poor GPS Coverage—The unit cannot acquire the nec-
essary number of satellites to compute a position. Try
another location with a clearer view of the sky.
Power Down and Re-init—The unit cannot calculate a
position due to abnormal satellite conditions. Turn power
off and use other means to verify the last position shown.
Try the unit again later, possibly in a differ
ent location. The GPS III uses an on-screen message indicator to alert you to important infor-
mation. Whenever the message appears, press ENTER to acknowledge the message
and return to the previous page you were viewing. Messages are provided for system
status, waypoint/route editing, battery condition, etc. For your safety, pay careful attention to all messages.
APPENDIX E
Messages
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							RAM Failed—The GPS III has detected a failure in its
internal memory. If the message persists, the GPS III is
unusable and should be taken to an authorized GARMIN
service center.
Received Invalid Waypoint—A waypoint was received
during upload transfer that has an invalid identifier.
Receiver Failed—A 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.
ROM Failed—The permanent memory has failed and
the unit is not operable. Take your unit to an authorized
GARMIN dealer for repairs.
Route Already Exists—You have attempted to name a
route with the same name currently in use with an exist-
ing route. Enter a different name for the route.
Route Full—You have attempted to add more than 30
waypoints to a route.
Route Memory Full—Route memory is full and no
additional routes can be added from another GPS III or
uploaded from a PC.
Route Waypoint Deleted—The waypoint being deleted
was part of a route. The deleted waypoint is removed
from waypoint memory and from the route.
RTCM Input Failed—DGPS data being received has
been lost. You are no longer receiving the beacon signal.Searching the Sky—
The GPS III is in
searching the sky for
almanac data or the unit is in AutoLocate mode.
Steep Turn Ahead—This message appears approxi-
mately one minute prior to a turn that requires a bank
angle in excess of 25 degrees in order to stay on course.
Stored Data Lost—All waypoints, routes, time, and
almanac data have been lost due to battery failure, or the
receiver’s memory has been cleared.
Timer Expired—
The countdown timer has expired.
Track Log Already Exist—The name selected for the
track log is identical to another track log already stored
in memory.
Track Memory Full—You have used all track log points
in the GPS III. (The unit holds approximately 1900
points in the active track log.) Delete unwanted track
points to make room for new entries.
Waypoint Memory Full—You have used all 500 way-
points in the GPS III. Delete unwanted waypoints to
make room for new entries.
Waypoint Already Exists—The name you are entering
already exists in the GPS III’s memory.
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APPENDIX E
Messages
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							AdindanAdindan- Ethiopia, Mali, Senegal, Sudan
AfgooyeAfgooye- Somalia
AIN EL ABD ‘70AIN EL ANBD 1970- Bahrain Island, Saudi
Arabia
Anna 1 Ast ‘65Anna 1 Astro ‘65- Cocos Isl.
ARC 1950ARC 1950- Botswana, Lesotho, Malawi,
Swaziland, Zaire, Zambia, Zimbabwe
ARC 1960ARC 1960- Kenya, Tanzania
Ascnsn Isld ‘58Ascension Island ‘58- Ascension Island
Astro B4 SorolAstro B4 Sorol Atoll- Tern Island
Astro Bcn “E”Astro Beacon “E”- Iwo Jima 
Astro Dos 71/4Astro Dos 71/4- St. Helena 
Astr Stn ‘52Astronomic Stn ‘52- Marcus Island
Astrln Geod ‘66Australian Geod ‘66- Australia, Tasmania Island
Astrln Geod ‘84Australian Geod ‘84- Australia, Tasmania Island
Bellevue (IGN)Efate and Erromango Islands
Bermuda 1957Bermuda 1957- Bermuda Islands
Bogata ObservBogata Obsrvatry- Colombia
Campo InchspeCampo Inchauspe- Argentina
Canton Ast ‘66Canton Astro 1966- Phoenix Islands
CapeCape- South AfricaCape CanavrlCape Canaveral- Florida, Bahama Islands
CarthageCarthage- Tunisia
CH-1903CH 1903- Switzerland
Chatham 1971Chatham 1971- Chatham Island (New Zealand)
Chua AstroChua Astro- Paraguay
Corrego AlegrCorrego Algre-Brazil
DjakartaDjakarta (Batavia)- Sumatra Island (Indonesia)
Dos 1968Dos 1968- Gizo Island 
(New Georgia Islands)
Easter Isld 67Easter Island 1967
European 1950European 1950- Austria, Belgium, Denmark,
Finland, France, Germany, Gibraltar, Greece,
Italy, Luxembourg, Netherlands, Norway,
Portugal, Spain, Sweden, Switzerland
European 1979European 1979- Austria, Finland, Netherlands,
Norway, Spain, Sweden, Switzerland
Finland HayfrdFinland Hayford- Finland
Gandajika BaseGandajika Base- Republic of Maldives
Geod Datm ‘49Geodetic Datum ‘49- New Zealand
Guam 1963Guam 1963- Guam Island
Gux 1 AstroGux 1 Astro- Guadalcanal Island
Hjorsey 1955Hjorsey 1955- Iceland
The following are the map datums available for the GPS III. Menu Page abbre-
viations are listed first, followed by the corresponding map datum name and area.
The default map datum for the GPS III is WGS 84.
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APPENDIX F
Map Datums
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