User Manual

CrossCheck CDPD Mobile Unit Manual
59
Operation
3
3.3
GPS Receiver Operation
At power-up, the GPS receiver initializes with the last-known position.
Using this information, the GPS receiver acquires satellite signals.
• During the satellite acquisition process—which normally
requires less than 2 minutes—the green GPS LED blinks.
• Once three or more satellites are acquired, the GPS receiver
computes positions, course, speed and time fixes, and the GPS
LED remains on.
A blinking GPS LED indicates that the GPS receiver is not tracking
enough satellites to calculate a current position. This occurs
occasionally when the vehicle is obscured from satellite signals by
terrain, buildings, trees, tunnels or other structures. During this
period—called satellite reacquisition—the GPS receiver continuously
searches for the obscured satellites and expands its search to other
satellites to continue position computations. For brief blockages, the
GPS receiver normally reacquires a lost satellite signal and resumes
position fixes in less than 2 seconds.