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Section 1
Introduction to
NavTalk Pilot
xviii
6
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. You'll learn how to
initialize your new NavTalk Pilot on page 61.
Initialization is only necessary under the following
conditions:
• The first time you use your receiver.
• 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 Pilot 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 determine how fast you get a position fix—or if
you get a fix at all. GPS signals are relatively 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.
Once the NavTalk Pilot has calculated a position fix,
you'll usually have anywhere from five to twelve satellites in
view. The receiver will then continuously select 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.
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