Garmin GPS II - Manual (Page 9)

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What is GPS?
GPS is a system of 24 satellites which circle the earth twice a day in a very pre-
cise orbit and transmit information to earth. The GPS II must continuously “see” at
least three of these satellites to calculate your position and track your movement.
By using an almanac (a timetable of satellite numbers and their orbits) stored in
the receiver’s memory, the GPS II 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 or given the opportunity to find itself, or
“initialize.” Once you initialize the unit to a position, it will usually compute a fix
within a few minutes.
Initialization is only necessary under the following conditions:
• The first time you use your GPS II (from the factory).
• After the GPS II has been moved over 500 miles from the last time you
used it (with the power off).
• If the GPS II’s memory has been cleared and all stored data has been lost.
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GPS II 7/23/98 4:03 PM Page 3