Location calculation is performed by way of two redundant functions. It is used for orientation purposes on the electronic map and as service information in an emergency.
GPS, in conjunction with the BMW navigation system, consists of an aerial and a receiver which evaluates the satellite data received via the aerial and transfers the calculated vehicle position to the navigation computer.
GPS reception is only possible when unobstructed view of the sky is ensured.
If GPS reception is not possible, the current location can also be input by hand. Essentially, the navigation computer calculates the current position from the previous position and the distance covered. The distance covered is made up of the distance travelled (wheel-speed sensors) and the change of direction (gyro). This information is permanently compared with the road-map and GPS information. Major discrepancies when driving on motorways/freeways point to GPS reception problems.
The navigation computer evaluates the signals of the ABS wheel-speed sensors and calculates from them the distance travelled. The standstill pulse is also displayed in the diagnosis request. The pulses can fluctuate between 0 and 1 at a standstill. The number of pulses increases with the wheel speed.
The gyro is an inertia sensor which records the forces which occur during a change in direction and transfers this data to the navigation computer in the form of a voltage change. This gyro is fitted in the casing of the navigation computer.