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Clock Alarmuses the internal clock to provide an ‘Alarm Clock’ message at the time
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
Setup Menu: Alarms
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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
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
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
Setup Menu: Position
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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
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.
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
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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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.
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
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
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
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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