GF82.61-P-3006QMU Basic Position Finding, Function

GF82.61-P-3006QMU Basic Position Finding, Function
- with CODE (530) COMAND APS USA (with navigation system)







Basic position finding (dead reckoning) is the base function in continuous position finding. It is performed continuously by the navigation processor of the COMAND operating, display and controller unit (A40/3) with the ignition switched on (circuit 15 On). After switching off the ignition (circuit 15 OFF) the current position is stored.

The following data are required for basic position finding (dead reckoning):
^ Travel distance covered
^ Direction of travel (backwards or forwards)
^ Vehicle course

Distance traveled
The navigation processor of the COMAND operating, display and controller unit (A40/3) receives the wheel speed signals for calculation of the distance traveled from the ESP and BAS control unit (N47-5) over the Controller Area Network bus class C (engine compartment) (CAN-C). The evaluation of the wheel speed signals shows the distance traveled.

Direction of travel
The signal for reversing, which is transferred by the EIS [EZS] control unit (N73) via the Controller Area Network bus class B (interior) (CAN-B), allows the navigation processor of the radio and navigation unit to recognize the direction of motion (forwards or backwards).

Vehicle course
The data from the yaw rate and lateral acceleration sensor (B24/15) and the sequence of locations calculated with the Global Positioning System (GPS) are used by the navigation processor to calculate the vehicle course.

The difference in the calculated mileage and the mileage actually covered between 2 turnoff points is used to automatically recalibrate the tire circumference (necessary due to tire wear).

Position finding errors during basic position finding (composite positioning)
Rolling backwards without the transmission being shifted into reverse gear is evaluated as moving forwards and can lead to temporary errors in location finding. Rolling when the ignition is switched off (circuit 15 OFF) or transporting the vehicle can also distort the position finding.
In both cases, this deviation is automatically corrected by the navigation processor on receipt of GPS data.

Calibration
Wheel calibration is necessary following a tire change. This requires entry of the tire size and coding of the tread depth. Entries are made using STAR DIAGNOSIS or directly on the COMAND operating, display and controller unit (A40/3). A special calibration journey is not required.