Garmin NavTalk - Manual (Page 17)

SECTION 1
Introduction To
NavTalk
5
4. The service provider will ask you questions about
the type of service options you desire and then
program your NavTalk accordingly.
1.3 GPS Navigation Overview
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 NavTalk 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 a position.
By using an almanac (a timetable of satellite num-
bers and their orbits) stored in the receiver’s memory,
the NavTalk 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 typ-
ically compute a fix within a few minutes. We’ll show
you how to initialize your new NavTalk on page 65.
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 been lost.
Because the NavTalk relies on satellite signals to pro-
vide you with navigation guidance, the receiver needs to
have an unobstructed, clear view of the sky for best per-
formance.
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