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Batter y Installation
The GPS III operates on 4 AA batteries (not included), which are installed at the
base of the unit. These batteries provide up to 8 hours of continuous use.
Rechargeable NiCad or lithium batteries may also be used.
NOTE: The on-screen battery level indicator is calibrated for alkaline batteries,
and will not be accurate when using NiCad or lithium batteries (see page 69).
To install the batteries:
1. Flip up the metal ring at the base of the unit, and turn the ring 90˚ counterclockwise.
2. Install the batteries and close the battery compartment door. When replacing the
GPS III’s batteries, observe the polarity markings engraved in the plastic case.
3. Lock the door in the closed position by rotating the metal ring 90˚ clockwise.
Battery life varies due to a variety of factors, including temperature and
backlighting. You may find that the battery life varies in different conditions and
that lithium batteries provide longer life in colder conditions. An internal 10-
year lithium battery will retain your data while you’re changing batteries.
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What is GPS?
The Global Positioning System (GPS) is a system of 24 satellites which circle the
earth twice a day in a very precise orbit and transmit information to earth. The GPS
III must continuously “see” at least three of these satellites to calculate your position
and track your movement. At times, additional satellites may be needed to determine
By using an almanac (a timetable of satellite numbers and their orbits) stored in
the receiver’s memory, the GPS III can determine the distance and position of any
GPS satellite and use this information to compute your position.
Your GPS receiver can only see satellites above the horizon, so it needs to know
what satellites to look for at any given time. To use this almanac data, your GPS
needs to either be told its general location (“initialized”) or given the opportunity to
find itself. Once you initialize the unit to a position, it will typically compute a fix
within a few minutes. We’ll show you how to initialize your new GPS III on page 5.
Initialization is only necessary under the following conditions:
• The first time you use your receiver (new from the factory).
• After the receiver has been moved over 500 miles (with the power off) from
the last time you used it.
• If the receiver’s memory has been cleared and all internally stored data has
Because the GPS III 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. In a nutshell, the GPS receiver’s view of the sky will generally deter-
mine how fast you get a position fix—or if you get a fix at all. GPS signals are rela-
tively weak and do not travel through rocks, buildings, people, metal, or heavy tree
cover, so remember to keep a clear view of the sky at all times for best performance.
Hold the receiver at a
comfortable height with the
antenna pointing up.
When new (or if a position
cannot be determined after 10
minutes), the GPS III will
prompt you to initialize the
receiver. The unit needs a
starting position to determine
which satellites are in view.
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Once the GPS III has calculated a position fix, you’ll usually have anywhere from
five to twelve satellites in view. The receiver will then 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 three-dimensional
(3D) fix, it can maintain a two-dimensional (2D) fix with only three satellites. A
three-dimensional fix means the unit knows its latitude, longitude, and altitude, while
a two-dimensional fix means the unit knows only its latitude and longitude.
Initializing Your GPS III
To initialize the GPS III, take the receiver outside and find an open area where the
antenna has a clear view of the sky. You may either hold the receiver at a comfortable
height with the antenna pointing up (see page 4), or mount the receiver on the dash of
a vehicle (Appendix A) or on a bike. (Likewise, when you use your GPS III in a
vehicle, make sure the antenna is pointing up.)
To turn the GPS III on, press and hold the red power key.
The Welcome Page will be displayed while the unit conducts a self test. Once
testing is complete, the Welcome Page will be replaced by a warning page, then by the
Satellite Status Page. A message will inform you to “select initialization method”. (If the
initialization prompt has not automatically appeared, press MENU and highlight
To initialize your unit:
1. Press ENTER to acknowledge the message and see a list of initialization options.
2. Use the rocker keypad to highlight ‘Use Map’, and press ENTER.
3. Use the rocker keypad to point the map cursor to your approximate location (within 250
miles). You may also wish to use the IN and OUT zoom keys to make it easier to identify
your approximate position.
4. Press ENTER to select the position and begin searching for satellites.
Check the Satellite Status
Page for ‘2D Navigation’ or
‘3D Navigation’ to verify a
The Welcome Page is
displayed when the GPS III is
first turned on. During this
time the receiver is conducting
a self test.
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This usually provides a position fix in 1 minute. You’ll know you have a fix when
the unit automatically transitions from the Satellite Page to the Map Page (shown
left). Your receiver is now ready to use!
To turn the unit off:
1. Press and hold the red power key for 1 second.
If you have trouble initializing or getting a position fix, check the following:
• Does the receiver have a clear view of the sky?
If there are large buildings or mountains, or if there is heavy tree cover, the
receiver may not be receiving enough satellite signals to calculate a fix. Also, if
you’re using the GPS III on a car dash, make sure the unit is placed so that it has
the clearest possible view of the sky. Your GPS will only be able to detect satel-
lites that it can “see” through your vehicle’s windshield. Depending on the slope
of your dash or the overall surface area of the window, it may be necessary to
mount an external antenna on your vehicle’s roof or trunk in order to give the
unit a better view of the sky. (Contact your local GARMIN dealer and inquire
about the GA 26 low-profile remote antenna, part number 010-10052-02.)
• Have you selected the right area when initializing?
Check for the correct approximate position on the Map Page (press PAGE until
the Map Page appears; see pages 7 and 10), or reselect your approximate
location to restart the initialization.
• Have you moved more than 500 miles from the last calculated position
with the receiver off?
Reinitialize the receiver by selecting your approximate position on the map, or
select ‘AutoLocate’ from the Satellite Status Page options (see page 29).
To initialize the GPS III,
designate your approximate
location directly on the map
display. Use the rocker keypad
and IN/OUT zoom keys to
position the cursor on the map.
Once the GPS III has a posi-
tion fix, it will automatically
transition from the Satellite
Status Page to the Map Page.
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To turn the GPS III back on, press and hold the red power key.
The GPS III features six main pages which are linked together in a chain. You can
quickly scroll through the pages in either direction using the PAGE or QUIT keys. Let’s
briefly tour each of these pages in order to give you some insight into how they help
you navigate. We’ll go over all of them in more detail in the reference section.
Press the PAGE key to move
through each of the main
pages in normal fashion.
Press the QUIT key to
sequence through the main
pages in reverse order.
Main Page Sequence
Compass PageHighway Page
Map PageActive Route Page
Position PageSatellite Status Page
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