GF82.61-P-3006GH Basic Location Finding, Function

GF82.61-P-3006GH Basic Location Finding, Function
- with CODE (352a) COMAND operating and display system
- except CODE (491) U.S. version
- except CODE (498) Japanese version







Basic location finding (compound position finding)
Refers to the basic function of the constant position finding. This is carried out constantly by the navigation computer when the ignition is switched on, and is not dependent on the CD-ROM map. The current position is stored after the ignition is switched off.

The following information is calculated with the aid of basic location finding:
- Travel distance
- Direction of motion (forward or reverse) and
- Vehicle alignment.

The basic position finding is performed approx. 1 x every second.

Mileage covered
The navigation computer receives the signals output by the front right wheel speed sensor (L6/2) from the traction system control module (N47) via a discrete line.

The evaluation of the wheel speed sensor signals determines the travel distance.

Direction of motion
The navigation computer recognizes the direction of motion (forward or reverse) from the reverse signal (comes from the CAN engine compartment).

Vehicle alignment
From the data from the rate of rotation sensor (gyrosensor) and the sequence of the locations calculated with GPS the navigation computer calculates the vehicle's orientation (points of the compass).

The difference between the calculated and the actual travel distance between two turn-off points is used for the automatic recalibration of the tire circumference (necessary because of the tire wear).

Position finding errors during basic position finding
Rolling backwards without the reverse gear engaged is evaluated as forward motion, and may lead to an error in the location finding. Rolling with the ignition switched off or vehicle transportation also falsify map matching.

In both cases, this deviation is automatically corrected by the navigation computer on receipt of GPS data.

Calibration
A wheel calibration must be performed after a tire has been changed. In order to achieve this, it is necessary to input the tire size, e.g.:
- 225 / 060 / 016

and the code, whether
- new (depth of tread approx. 5 - 10 mm), or
- used tires (depth of tread approx. 3 - 5 mm)

have been installed. The entry is made using the STAR diagnostics tool or directly on the COMAND operating, display and control module (A40/3).

A special calibration trip is not necessary.