Navigation Mode
The present position is known at the start of the journey as it is either still stored or is checked/established at the time. When the vehicle is being driven, the navigation system receives the "distance covered" information from the DSC control unit via the bus (PT-CAN/junction box control unit/K-CAN).
The travel data from the wheel speed sensors is transmitted as a bus message. It is broadcast on the PT-CAN by the DSC. From there it is transferred to the K-CAN by the junction box control unit and passed to the navigation system.
The rear left wheel speed sensor supplies the information necessary for this purpose to the DSC control unit. If that wheel speed sensor fails, the rear right wheel speed sensors takes over.
The gyro sensor determines any changes in direction such as when cornering. Changes in altitude are not detected by the two dimensional gyro sensor. The current position can be determined by combined evaluation of the "distance covered" and "driving direction". The position calculated in this way is compared to the navigation data stored on the DVD.
If considerable deviations occur (incorrect calculations due to inaccurate sensor data, outdated map data), priority is given to the current position determined by the GPS. During normal operation, the position is therefore determined during navigation operation based on correspondingly processing the wheel speed and yaw rate sensor information.
The footwell module makes available the "reversing" information in the form of a bus message to the navigation system and this information is taken into account in the position calculation.
On manual transmission vehicles, the reverse gear switch is located on the manual gearbox.
On automatic transmission vehicles, the reverse gear information is provided by the transmission control unit that detects the status of the selector lever position switch.
After the navigation computer has been disconnected from the power supply, it can take up to 10 minutes before the navigation system determines the current position as an update of the almanac data and the received satellite data is necessary in this case.
Delayed positioning can also occur after longer parking periods (e.g. holidays). The following aids are available for route guidance purposes:
- Display of current position on the screen
- Direction arrows as orientation for further road routing
- Distance information up to the next change in direction (turn off)
- Voice announcements for further route guidance
- Distance to destination
- Route list and destination list
- Calculated route indicated by a white line to the destination in the map presentation