Garmin GPSMAP 175 - Manual (Page 9)

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GETTING STARTED
Acquiring Satellite Signals
Acquiring Satellite Signals
Because the GPSMAP 175 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. What exactly does this mean? 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 large obstructions made of metal, rock, or wood, for
example.
Once the GPS has calculated a position fix, you’ll usually have anywhere
from four to twelve satellites in view. Your GPSMAP 175 will now
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 3D fix (latitude, longitude and
altitude), the GPSMAP 175 can maintain a 2D fix (latitude and longitude
only) with just three satellites.
Before You Initialize
Take your GPSMAP175 outside and find a large, open area (try a nearby
park) that has a clear view of the sky from horizon to horizon. Hold the
receiver at a comfortable height, at arm’s length from your body with the
built-in antenna (the top part above the display) parallel to the ground.
175 Manual 7/31/98 3:55 PM Page 5