GF82.95-P-3000RE Position Finding, Function
GF82.95-P-3000RE Position Finding, Function
- with CODE (349) E Call emergency call system
- with CODE (498) Japan version
- up to 31.5.04
- with CODE (855) TELE AID
- up to 30.6.04
- with CODE (494) USA version
Position finding with GPS
Basic position finding (dead reckoning)
Component Identification:
The global positioning system (GPS) is a satellite supported position finding system established by the US Defense Department. It is a toll-free service available throughout the world. 26 satellites are currently orbiting the earth on 6 different trajectories. The GPS satellites continuously transmit time and position data (longitude/ latitude).
Position finding
The vehicle location is determined parallel with two methods supplementing each other. The methods are called GPS location finding and basic location finding (dead reckoning).
GPS location finding:
The GPS location finding is particularly valuable when driving outside of the digitized map area and following vehicle transport (e.g. train, ferry or towing).
A repeated GPS location finding (following satellite reception interruption) can take several minutes (when the unit is initially started up to 20 minutes).
The computer and GPS receiver unit are integrated into the TELE AID control unit (A35/8). If signals are received from at least 3 satellites via the GPS antenna (A2/23), it is possible to calculate the position and the accuracy of the location finding of the receiver (vehicle) (positioning accuracy 100 m).
Moreover, the direction of motion is determined with the aid of the sequence of the locations calculated with GPS.
The basic position finding is determined parallel to the GPS position finding.
Basic position finding (dead reckoning)
For the basic location finding of the vehicle, the D2B CTEL and TELE AID transmitter-receiver (A35/17) requires the following information:
^ The left front rpm sensor (L6/1) and right front rpm sensor (L6/2) signals processed by the ESP control unit, PML and BAS (N47-5).
^ The number of pulses of the left front rpm sensor (L6/1) is a measure for the travel distance.
^ The data from the yaw rate sensor integrated in the TELE AID control unit (A35/8).
From the data from the yaw rate sensor the TELE AID control unit (A35/8) calculates the vehicle alignment (sky direction).
^ The data on the direction of motion.
^ Stop lamp switch (S9/1) signal.
The reverse lamp signal indicates whether the vehicle is moving forward or backward.
The basic position finding is continuously performed (1 time per second) by the TELE AID control unit (A35/8) at "circuit 15R: ON". The momentary vehicle position (longitude/latitude) is calculated from the path traveled under consideration of the vehicle alignment and direction of motion.
If the computer calculates that the basic location finding is less precise than the GPS location finding, the currently calculated position is corrected with the aid of the GPS data.
If an accident occurs, the TELE AID control unit (A35/8) automatically generates an emergency call telegram which contains the position data of the vehicle and transmits this over the vehicle's mobile phone system (digital network). The emergency call signal reaches the service provider.
With the equipment there (graphics-capable workstation and electronic road data base) the exact location of the vehicle can be determined with the aid of position data.
Errors with basic position finding
Rolling backwards without the reverse gear engaged is evaluated as forwards motion, and may lead to an error in the location finding. Rolling with the ignition switched off or vehicle transportation also falsify location finding.
The deviation is automatically corrected by the computer in the TELE AID control unit (A35/8) in both cases when the GPS data are received.
