Navigation, function

General

Navigation includes the vehicle location finding function, determination of direction and distance to the destination (according to destination entered) and the measures required to reach this destination.

Navigation therefore includes the following terms:

 Location finding

 Route calculation

 Destination guidance

Location finding

The location of the vehicle is continuously calculated by the auto-pilot system (APS) with the aid of the following procedures:

 GPS location finding

 Basic location finding (dead reckoning)

 Map-supported location finding (map matching).

The data from these three procedures is automatically corrected when they supply different information to the APS navigation processor (A85).

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Route calculation

The route is calculated and updated by the APS navigation processor (A85) according to the destination entered.

The optimum route is calculated by the APS navigation processor from the map data read from the CD-ROM, the correct position and the destination entered.

Optimization of the route is accomplished according to the estimated driving time and not according to the shortest distance. The streets read in from the CD-ROM and attributes such as one-way streets, turning prohibition, street classes, etc. are taken into consideration. It is possible to manually inhibit the use of certain streets. A menu on the radio and navigation operating unit (A9) allows selection between the following routes for guidance:

 Shortest route

 Fastest route

 Route according to own selection

APS navigation processor (A85) makes up a list of streets and turns for guidance. Points located outside the digitalized map area are not taken into consideration in calculating the route.

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 The route can only be calculated inside of the digitalized map area.

Route updating

Route updating is a subfunction of route calculation. It is used when the driver deviates from the calculated route and does not respond to the request "Please turn around if possible". In this case the data for the location and destination are recalculated and the route is updated.

 Completion of route calculation is a prerequisite for destination guidance.

Destination guidance

After entering the destination on the APS radio and navigation operating unit (A9) and calculation of the route in the APS navigation processor (A85), the destination guidance is started. If the driver leaves the recommended route, the "Route updating" feature is started.

 Complete navigation is not available outside of the CD-ROM map boundaries. Only the straight line route to the destination with distance is indicated. The words "NO MAP" appear on the display.

Loading voice data

The data for voice output during destination guidance is stored on the CD ROM.

These data is read from the CD-ROM by the APS navigation processor (A85) and stored in the memory. After the voice data has been loaded completely, the following announcement is given:

"Voice data loaded"

Loading the voice data requires approx. 20 s.

 If the power supply to the auto-pilot system is interrupted, while loading the voice data, the voice data is locked and must be reloaded.

 Following a short power interruption (< approx. 15 s), the voice data must be reloaded by the user, because it may be erratic (recognizable on blanks, not understandable) or deleted completely.

 After a longer interruption of the power (approx. >15 s),
the voice data is lost and is reloaded automatically.