Basic position finding, function - GF82.61-P-3006CA
MODEL 215, 220 with CODE (352a) COMAND operating and display system with CODE (494a) USA version
Basic position finding
Basic position finding (compound position finding) is the basic function of continuous position finding. When the ignition is switched on it is carried out continuously by the navigation processor and is independent of the DVD map. After the ignition is switched off, the current position is stored for the duration of the run on period.
The following information is calculated with the aid of basic position finding:
- Distance traveled
- Direction of travel (forward or reverse)
- Vehicle orientation
Basic position finding is carried out approx. once per second.
Distance traveled
Information from the left front rpm sensor (L6/1) and right front rpm sensor (L6/2) of the non-driven wheels is passed to the ESP, SPS [PML] and BAS control unit (N47-5) and (CAN-C) navigation processor via discrete wiring and the engine compartment CAN (CAN-C), respectively.
The evaluation of the rpm signals gives the distance traveled.
In vehicles as of 1.9.03, the navigation processor (N41/1) is installed as a separate control unit on the left-hand side of the trunk.
Direction of travel
The navigation processor recognizes the direction of motion (forward or reverse) from the reverse signal.
Vehicle orientation
The navigation processor calculates the vehicle's orientation (compass direction) using the difference between the rpm sensor signals, the data from the yaw rate sensor and the sequence of the locations calculated using GPS. The difference in the calculated mileage and the mileage actually covered between two turn-off points is used to automatically recalibrate the tire circumference (necessary due to tire wear).
Errors with basic position finding
Rolling backwards without the reverse gear engaged is evaluated as forwards motion, and may lead to an error in position finding.
Rolling with the ignition switched off or vehicle transportation also falsify position finding.
However, the calculated position is automatically corrected by the navigation processor when the GPS data is received.
Navigation is not possible if the driver removes the navigation DVD from the drive.
Calibration
Wheel calibration is necessary following a tire change. The appropriate information must be entered:
- Tire size (e.g. 225/60/16)
- New depth of tire tread (approx. 5 - 10 mm)
- Used tires (depth of tread approx. 3 - 5 mm)
This information is entered using STAR DIAGNOSIS. A special calibration trip is not required.
| Global positioning system (GPS) position finding, function | GF82.61-P-3007BA |