GF82.61-P-2010RIJ Position Finding and Destination-Oriented Navigation, Function

GF82.61-P-2010RIJ Position Finding And Destination-oriented Navigation, Function
- with CODE (527) COMAND APS with single DVD drive (with navigation)

Function requirements
^ Status "Circuit 30 ON" for Global Positioning System (GPS) position finding
^ Status "Circuit 15R ON", for basic position finding
^ COMAND operating, display and controller unit (A40/3) activated via "ON" button
^ "Navi" menu selected
^ Current navigation data loaded
^ Destination has been entered
^ No error in GPS antenna system
^ Signals available from at least 3 GPS satellites

General position finding
GPS is available worldwide. The GPS satellites permanently transmit time and position data (longitude and latitude). GPS position finding is irretrievable after vehicle transport (e.g. by train or ferry or after towing). A new GPS position (after interruption of the satellite reception) can take several minutes (up to 20 minutes when the equipment is commissioned).
Basic position finding runs parallel to GPS position finding. The position finding function consists of the following component functions:
^ Function sequence for GPS position finding
^ Basic position finding function sequence
^ Destination-oriented navigation function sequence

Function sequence for GPS position finding
The global positioning system receiver is integrated into the COMAND controller unit. It receives the GPS signals from the GPS antenna (A2/23) over the following path:
- Direct line
- COMAND controller unit

The GPS signals are used by the COMAND control unit to calculate the current vehicle position (receiver). In addition, the vehicle's direction of travel is determined with the aid of the sequence of the locations calculated with GPS.

Possible problems in GPS signal reception
Since GPS operates in the giga hertz (GHz) range (microwaves) and the signals are weak, reception interference can occur as a result of the following events:
- Atmospheric interference, e.g. inclement weather, water vapor, fog
- Multiple path reception due to reflection of the signals
- Signal blocking, e.g. in built-over areas and in tunnels, through high-rise buildings, trees

Basic position finding function sequence
For basic position finding the COMAND control unit requires the following information:
- Wheel speed signals
- Distance traveled data
- Vehicle alignment (cardinal points)
- Direction of travel data (forwards or backwards)

The wheel speed signals are recorded by the following rpm sensors:
- Left front rpm sensor (L6/1)
- Right front rpm sensor (L6/2)
- Left rear rpm sensor (L6/3)
- Right rear rpm sensor (L6/4)

The wheel speed signals are received by the COMAND control unit from the rpm sensors in the following way:
- Direct line
- ESP, SPS [PML] and BAS control unit (N47-5)
- Engine compartment CAN
- Central gateway control unit (N93)
- Interior CAN

The travel distance data is also determined from the wheel speeds.

The vehicle alignment data (change in angle) is internally processed by the turn rate sensor (gyro sensor)integrated into the COMAND controller unit.
The data on the direction of travel (forward or back) is received by the COMAND controller unit from the central gateway control unit via the interior CAN. The COMAND controller unit uses the travel distance covered to calculate the coupled position, taking the vehicle alignment into consideration as well as the direction of travel.
This coupled position is compared with the GPS data (longitude, latitude, direction). This position data is then compared with the map data (map matching). To recognize the street level (elevated highway), the vertical angle (from 3D gyro) and the data of the Electronic Toll Collection System (ETC) gates and the Vehicle Information and Communication System (VICS) beacons are also considered (dealer option).

Error during position finding
Basic position finding is falsified when a vehicle rolls backwards with "circuit 15 OFF" (ignition switched off) or if it is transported somewhere. In both instances the deviation is automatically corrected by the COMAND controller unit's integrated navigation processor upon reception of GPS data.

Destination-oriented navigation function sequence
The destination-oriented navigation consists of the following subfunctions:
^ Destination-oriented navigation function sequence through voice output
^ Destination-oriented navigation function sequence through visual display
^ VICS function sequence over FM multiplexer
^ Dynamic route guidance function sequence, VICS (dealer option)

Destination-oriented navigation function sequence through voice output
The integrated navigation processor continuously compares the route calculation data with the position finding data and uses the data to deduce measures for further destination-oriented navigation. The destination-oriented navigation voice output is emitted over direct lines at the following speakers:
- Left door speaker group (H4/1)
- Right door speaker group (H4/2)

Destination-oriented navigation function sequence through visual display
The signals for visual display of the navigation (map navigation) are generated by the COMAND controller unit and shown on the display of the COMAND controller unit.

VICS function sequence over FM multiplexer
The driver is provided with vital information by the VICS on the current traffic situation. Traffic impairments and traffic jams are shown on the map, however they are not incorporated into the dynamic route guidance. The antenna signal's path is as follows:
- Windshield antenna
- Direct line
- Left antenna amplifier module (A2/64)
- Direct line
- COMAND controller unit

The VICS information is processed in the FM multiplexer integrated into the COMAND controller unit. Finally, the information is shown on the display of the COMAND controller unit. In addition, the FM multiplexer can also receive additional information, e.g. on the weather or earthquakes

Dynamic route guidance function sequence, VICS (dealer option)
The dynamic route guidance requires the VICS antenna (A2/96) (dealer option). The VICS function is integrated into the COMAND controller unit. The VICS antenna communicates with the VICS beacons (transmission rods) installed along the road, which transmit FM or infrared signals. Received signals are sent directly to the COMAND control unit where they are decoded. The traffic messages are stored and made available to the navigation processor in the following way:
- VICS antenna
- Direct line
- COMAND controller unit

The traffic data recorder decodes the traffic information and forwards it to the navigation processor upon request. The navigation processor makes the decision whether the route should be changed. If necessary, a message that the route was changed is output via the vehicle speaker.