Global positioning system (GPS) position finding, function - GF82.61-P-3007PME
MODELS 203.0 /2 /7 as of 24.4.04 with CODE (525) MB Audio 50 APS radio
The Global Positioning System (GPS) is a satellite-supported location finding system set up by the US Department of Defense. It is a toll-free service available throughout the world. Various satellites constantly transmit time and position data.
Four satellites are needed for the first position calculation, thereafter three satellites are sufficient. Position finding by GPS is absolutely essential, especially in the case of journeys outside of the digitized map area and following vehicle transportation.
New position finding by GPS (following the interruption of satellite reception) may take several minutes (up to 20 minutes when commissioning the radio and navigation unit (A2/56)).
The navigation processor in the radio and navigation unit (A2/56) calculates the vehicle location and the accuracy of position finding from the satellite signals received and amplified by the GPS antenna (A2/23).
Every minute, approximately 50 recalculations are performed by the GPS.
The actual calculation is essentially based on measuring the times of the synchronously transmitted signals from the different 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. When the navigation processor determines that the basic position finding is less precise than position finding by GPS, the current calculated position is corrected with the aid of 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.
Possible interference in the reception of the signals by the Global Positioning System (GPS)
As GPS operates in the microwave range and the signals are weak, reception interference may occur. Causes for this are:
- Atmospheric interference, caused e.g. by weather, water vapor or fog
- Multi-path reception of the signals, e.g. due to signal reflections from building walls
- Shadowing effects on the signals, caused e.g. by superstructures, tunnels, tall buildings or trees
For reception it is necessary that no obstacle is located between the GPS antenna (A2/23) and the satellites. The location accuracy is approx. 100 m and less.
| Global positioning system antenna, location/ task | GF82.61-P-4107P | ||
| Radio and navigation unit, location/task/design/ function | GF82.61-P-4109PM |