Garmin GPS II - Manual (Page 10)

4
Satellite Signals
Because the GPS II relies on satellite signals to provide you with navigation guid-
ance, the receiver needs to have an unobstructed, clear view of the sky for best per-
formance. 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 GPS II has calculated a position fix, you’ll usually have anywhere from
four to eight satellites in view. The GPS II will then continuously select the best satel-
lites 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, the GPS II 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.
To prevent accidental battery
power loss, the GPS II will
automatically shut off 10 min-
utes after the last keystroke if
the unit is not tracking at least
one satellite and has never
acquired a position fix.
READ ME FIRST!
GPS II 7/23/98 4:03 PM Page 4