Garmin GPSMAP 175 - Manual (Page 10)

2 INTRODUCTION
Initialization
Initializing Your GPSMAP 175 for First-Time Use
Your GPSMAP 175 calculates your position and movement by tracking
signals sent from GPS satellites. Each of the 24 GPS satellites circle the earth
twice a day in a very precise orbit, and transmit information back to earth.
In order to determine a position fix, your GPS receiver needs to
continuously “see” at least three satellites.
Because a GPS receiver can only see satellites above the horizon, it needs
to know what satellites to look for at any given time. By using an almanac
(a timetable of satellite numbers and their orbits) stored in the receiver’s
memory, the GPSMAP 175 can determine the distance and position of any
GPS satellite.
To use this almanac data, your GPSMAP 175 needs to know where you
are, or be given the opportunity to “find itself.” Once you initialize the unit
to this position, the GPSMAP 175 will usually compute a fix within a few
minutes.
Remember, this process is only necessary under the following conditions:
• First-time use from the factory;
• The receiver has been moved over 500 miles from the last calculated
position with power off; or
• The receiver’s memory has been cleared and all stored data has been lost.
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175 Manual 7/31/98 3:55 PM Page 6