Position finding, function - GF82.95-P-3000SX

MODEL 215.3, 220.0 /1 with CODE (359) TELE AID emergency call system with CODE (494a) USA version 

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 parallel with 2 methods supplementing each other. The 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 receiver unit of the GPS are integrated in the emergency call system control unit (N123/4). If signals are received from at least 3 satellites via the GPS antenna (A2/23) (model 215) or the GPS antenna (A2/49a2) (model 220), it is possible to calculate the position and 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 

To find the basic position, which takes place in parallel to the GPS position finding, the emergency call system control unit (N123/4) requires the following information:

• The signals processed by the ESP, SPS [PML] and BAS control unit (N47-5) of 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), which get 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 over the Controller Area Network (databus/CAN bus) (CAN) diagnosis to the emergency call system control unit (N123/4).
• The data of the yaw rate sensor (gyrosensor) integrated in the emergency call system control unit (N123/4) (the emergency call system control unit (N123/4) uses the data of the integrated gyrosensor to calculate the vehicle orientation (direction)).
• The data about vehicle direction (forward or reverse)

The 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 travel distance in consideration of the vehicle alignment and direction of travel. If the navigation processor determines that the basic location finding is less accurate than the GPS location finding, the position currently calculated is corrected using GPS data. If an accident occurs, the emergency call system control unit (N123/4) automatically generates an emergency telegram that contains the position data of the vehicle and transmits it 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 backward with the ignition switched off or vehicle transportation also falsify position finding. The deviation is automatically corrected by the integrated navigation processor in the emergency call system control unit (N123/4) in both cases when the GPS data are received.