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

GF82.61-P-3006QN Basic Position Finding, Function
- with CODE (525) MB Audio 50 APS radio







Basic position finding (composite positioning) is the basic function of continuous position finding. It is carried out continuously by the navigation processor of the radio and navigation unit (A2/56) when the ignition is switched on and is independent of the navigation CD that has been read in. The current position is stored in the navigation processor after the ignition is switched off.

The following information is calculated with the aid of basic position finding (composite positioning):
^ 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 integral navigation processor receives the wheels speed signals from the ESP and BAS control unit (N47-5) via the class C (engine compartment) controller area network bus (CAN-C) . These wheel speed signals are evaluated to determine the distance traveled.

Direction of travel
The navigation processor of the radio and navigation unit (A2/56) detects the direction of travel (forwards or backwards) using the signal for reversing sent by the EIS [EZS] control unit (N73) via the class B (interior) controller area network bus (CAN-B).

Vehicle orientation
The navigation processor 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).

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 position finding. Rolling when the ignition is switched 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.

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.

This information is entered using STAR DIAGNOSIS or directly at the radio and navigation unit (A2/56). A special calibration drive is not required.