GF82.61-P-3006RM Basic position finding, function

GF82.61-P-3006RM Basic Position Finding, Function
- Model 230.474/475
- with CODE (527) COMAND APS (with navigation)








Basic position finding, function
Basic location finding (dead reckoning) is the basic function of continuous location finding. When the ignition is switched on, it is carried out continuously by the navigation processor (N41/1) and is independent of the digital versatile disk (DVD) map. The current position is stored after the ignition is switched off. The following information is calculated with the aid of basic position finding:
^ Distance traveled
^ Direction of travel (forward or reverse)
^ Vehicle orientation

The basic position finding (composite positioning) is performed approximately every 1 s.

Distance traveled
The navigation processor (N41/1) receives the wheels speed signals from the ESP, SPS [PML] and BAS control unit (N47-5) via the Controller Area Network Bus Class C (engine compartment) (CAN-C). These wheel speed signals are evaluated to determine the distance traveled.

Direction of travel
Via the signal for reversing that is transmitted by the EIS [EZS] control unit (N73) via the Controller Area Network bus class B (interior) (CAN-B), the navigation processor (N41/1) detects the direction of travel (forward or reverse).

Vehicle orientation
The navigation processor (N41/1) calculates the orientation (compass direction) of the vehicle from the data of the yaw rate sensor (gyro sensor) and the sequence of the positions calculated using the global positioning system (GPS). 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).

Errors with basic position finding
Rolling backwards without the transmission being shifted into reverse gear is evaluated as moving forwards and can lead to temporary errors in position finding. Rolling when the ignition is switched off or transporting the vehicle can also distort the position finding.

In both cases the deviation is corrected automatically by the navigation processor (N41/1) upon receipt of the GPS data.

The driving direction signal (forwards, backwards) is generated by the wheel speed sensors. This makes possible an exact recording of the distance traveled.

Calibration
Wheel calibration is necessary following a tire change. To do this, the input of tire size and the coding, whether new tires (depth of tread approx. 5 to 10 mm) or worn tires (depth of tread approx. 3 to 5 mm) have been fitted, is necessary. The input takes place via STAR DIAGNOSIS or directly at the COMAND operating, display and control unit (A40/3). A special calibration drive is not required.