Page 86 from 100
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,
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
Wiring / Interfacing
Data In Data Out
GPS III Connections (from back of unit)
GARMIN GBR 21 Beacon Receiver
GPS III A 7/21/98 8:52 AM Page 78
Page 87 from 100
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.
Antenna / Remote Mounting
GPS III A 7/21/98 8:52 AM Page 79
Page 88 from 100
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-
Battery Power Low—The batteries are low and should
Data Transfer Complete—The unit has finished
uploading or downloading information to the connected
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.
GPS III A 7/21/98 8:52 AM Page 80
Page 89 from 100
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
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.
The countdown timer has expired.
Track Log Already Exist—The name selected for the
track log is identical to another track log already stored
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.
GPS III A 7/21/98 8:52 AM Page 81
Page 90 from 100
AdindanAdindan- Ethiopia, Mali, Senegal, Sudan
AIN EL ABD ‘70AIN EL ANBD 1970- Bahrain Island, Saudi
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
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.
GPS III A 7/21/98 8:52 AM Page 82