Position finding, function - GF82.95-P-3000SK
MODEL 171.4 with CODE (359) TELE AID emergency call 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. The GPS satellites continuously transmit time and position data (longitude and latitude).
Position finding
The vehicle location is determined using two simultaneously operating methods that supplement each other. These methods are called GPS position finding and basic position finding.
GPS position finding
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 and the GPS receiver unit are integrated in the emergency call control unit (N123/4). If signals are received from at least 3 satellites via the GPS antenna splitter (A2/5) of the GPS antenna (A2/23) it is possible to calculate the position and the accuracy of the location finding of the receiver (vehicle). In addition, the vehicle's direction of travel is determined with the aid of the sequence of the locations calculated with GPS.
Basic location finding
In order to carry out the basic position finding that runs in parallel to the GPS position finding, the emergency call system control unit (N123/4) needs the following information:
- The signals from the left front RPM sensor (L6/1), right front RPM sensor (L6/2), left rear RPM sensor (L6/3) and right rear RPM sensor (L6/4) that are processed by the ESP and BAS control unit (N47-5) and sent to the central gateway control unit (N93) via the Controller Area Network Bus class C (engine compartment) (CAN-C). The central gateway control unit (N93) receives the message and transmits it on the diagnosis Controller Area Network (data bus/CAN bus) (CAN) to the emergency call system control unit (N123/4).
- The data in the yaw rate sensor (gyrosensor) that is integrated in the emergency call system control unit (N123/4) are used by the emergency call system control unit (N123/4) to calculate the vehicle alignment (point of compass).
- The direction of travel data (forward or reverse)
Basic position finding is performed continuously by the emergency call system control unit (N123/4) with "Circuit 15R ON". The current vehicle position (longitude and latitude) is calculated from the distance traveled, taking the vehicle alignment and direction of travel into consideration. If the navigation processor determines that basic location finding is less accurate than GPS location finding, the currently calculated position is corrected using the GPS data. If an accident occurs, the emergency call system control unit (N123/4) automatically generates an emergency call telegram which contains the vehicle position data and transmits these data over the vehicle's cellphone system. The emergency call signal reaches the service provider. With the equipment there, the exact position of the vehicle is determined using the position data.
Errors with basic position finding
Rolling backwards with "circuit 15 OFF" or transporting the vehicle also falsify position finding. The deviation is automatically corrected by the navigation processor integrated in the emergency call control unit (N123/4) in both cases when GPS data are received.
| GPS antenna, location/task | GF82.62-P-4107SK | |
| Antenna splitter, location/task | GPS | GF82.85-P-3112SK |
| TELE AID control unit, location/task/design/ function | GF82.95-P-4100SKU |