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

MODEL 230.4 as of 1.7.04 with CODE (359) TELE AID emergency call system with CODE (494) USA version 

The Global Positioning System (GPS) is a satellite-supported localizing system set up by the United States Department of Defense. It is a toll-free service available throughout the world. The GPS satellites continuously transmit time and position data (longitude/latitude).

Position finding 

The vehicle location is determined in parallel with two 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 GPS receiver unit are integrated in the emergency call system control unit (N123/4). When signals from at least 3 satellites are received by the GPS antenna (A2/23), it is possible to calculate the position and precision of the receiver location (vehicle). In addition, the vehicle's direction of travel is determined with the aid of the sequence of the locations calculated with GPS.

Basic position finding 

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

• The signals processed by the ESP, SPS and BAS control unit (N47-5) coming 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) sent over the Controller Area Network Bus Class C (engine compartment) (CAN-C) to the central gateway control unit (N93). The central gateway control unit (N93) receives the message and sends it via the diagnosis bus to the emergency call system control unit (N123/4).
• The data from the yaw rate sensor (gyrosensor) integrated in the emergency call system control unit (N123/4) (using the data from the integrated gyrosensor, the emergency call system control unit (N123/4) determines the vehicle direction (compass direction)).
• The data about direction of travel (forward or reverse)

The basic position finding is performed continuously by the emergency call system control unit (N123/4) with "Circuit 15R ON". The momentary vehicle position (longitude/latitude) is calculated from the travel distance, taking into consideration the vehicle orientation and direction of travel. If the navigation processor determines that the basic position finding is less accurate than the GPS position finding, the position currently calculated is corrected using GPS data. If an accident occurs, then the emergency call system control unit (N123/4) automatically generates an emergency call telegram that contains the vehicle position data and transmits this over the vehicle's cellular telephone 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. In both cases, the divergency is automatically corrected by the integral navigation processor in the emergency call system control unit (N123/4) when GPS data are received.