GF82.61-P-3007QN Global Positioning System(GPS) Position Finding, Function

GF82.61-P-3007QN Global Positioning System(GPS) Position Finding, Function
- with CODE (525) MB Audio 50 APS radio

The global positioning system (GPS) is a satellite-supported localizing system set up by the American Department of Defense. It is free and available worldwide. Various GPS satellites constantly transmit time and position data. 4 satellites are needed for the first position calculation, then 3 receivable satellites are sufficient. Starting GPS position finding again (following interruption of the satellite reception) may take several minutes (for initial startup of the device up to 20 min).

Every minute roughly 50 GPS new calculations of the location are performed.

Global positioning system (GPS) map matching, function
The navigation processor of the radio and navigation unit (A2/56) calculates the vehicle location and the accuracy of the position finding based on the satellite signals received and amplified by the GPS antenna (A2/23) (model 209.4, model 209.3 up to 31.5.06) or by the GPS antenna (A2/49a2) (model 209.3 as of 1.6.06). The actual calculation is based on the measurement of the transmission times of the signals transmitted synchronously by the various satellites. An important requirement here is the synchronism of the satellite clocks and of the receiver clock integrated in the radio and navigation unit (A2/56)
To this end the receiver is equipped with an automatic time correction, which in turn is made possible with the aid of the satellite signals.

When the navigation processor determines that basic location finding is less precise than GPS location finding, the currently calculated position is corrected with the aid of the GPS data. In addition to this the sequence of locations calculated by the GPS is used to determine the vehicle's route.

Possible interference when receiving GPS signals
Since GPS operates in the giga hertz (GHz) range (microwaves) and the signals are weak, reception interferences can occur as the result of the following events:
^ Atmospheric interference,
e.g. inclement weather, water vapor, fog
^ Diversity through reflections of the signals,
e.g. on house walls
^ Signal screening,
e.g. in built-up areas, tunnels, high buildings, trees

GPS reception therefore necessitates a clear view of the sky. Positioning accuracy is approx. 100 m.