Global positioning system (GPS) position finding, function with code 530 - GF82.61-P-3007SKU
MODEL 171.4 with CODE (530) COMAND APS USA (with navigation system)
The global positioning system (GPS) is a satellite-supported localizing system set up by the American Department of Defense. It is a toll-free service available throughout the world. Currently several satellites are on different orbits around the earth. The GPS satellites constantly transmit time and position data.
4 satellites are needed for the first position calculation, then 3 receivable satellites are sufficient. GPS position finding is irreplaceable for journeys outside the digitized map area and after vehicle transport (e.g. train or ferry journeys and towing). A new GPS position (after interruption of the satellite reception) can take several minutes (up to 20 minutes when the equipment is first set up).
The navigation processor (N41/1) calculates the vehicle location and the accuracy of the locating from the amplified satellite signals received by the GPS antenna (A2/23).
The actual calculation is essentially based on the measurement of the travel times of the signals sent synchronously by the various satellites. Here, an important prerequisite is that the satellite and receiver clocks are synchronized. For this purpose, the receiver has an automatic time correction feature which again is possible with the aid of the satellite signals. If the navigation processor (N41/1) determines that the basic position finding (dead reckoning) is less accurate than GPS position finding, the currently calculated position is corrected using the GPS data. In addition, the vehicle's course of travel is determined with the aid of the sequence of the locations calculated with GPS.
Approximately 50 GPS recalculations of the location take place per minute.
Possible interference when receiving GPS signals
Since GPS operates in the GHz range and the signals are weak, reception interference can occur as a result of the following events:
- Atmospheric interference, e.g. bad weather, water vapor, fog
- Multipath reception due to the reflection of the signals e.g. from walls of buildings
- Signal shading, e.g. in built-up areas, in tunnels, by high buildings and by trees
A prerequisite for good reception is that there are no obstacles between the GPS antenna (A2/23) and the satellite. Positioning accuracy is approx. 100 m.
| Operating, display and control unit, location/ task/design/function | GF82.85-P-3114SKU |