GF82.61-P-2010GQJ Position Finding and Destination-Oriented Navigation, Function
GF82.61-P-2010GQJ Position Finding And Destination-oriented Navigation, Function
- with CODE (527) COMAND APS with single DVD drive (with navigation)
- with CODE (498) Japan version
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
^ Destination has been entered
^ No error in GPS antenna system
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).
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 GPS receiver COMAND is integrated into the COMAND operating, display and controller unit. It receives the GPS signals from the GPS antenna (A2/93a6) via the following route:
- Direct line
- COMAND operating, display and controller unit
The GPS signals are used by the COMAND operating, display and controller unit to calculate the current position of the vehicle (receiver). In addition, the vehicle's direction of travel is determined with the aid of the sequence of the locations calculated with GP
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, snow
- 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
The COMAND operating, display and controller unit requires the following information for basic position finding:
- Wheel speed signals
- Vehicle orientation (change in angle)
- Direction of travel data (forwards or backwards)
- Last position
The wheel speed signals are detected 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 transferred to the COMAND operating, display and controller unit from the rpm sensors via the following route:
- Direct line
- ESP 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 data for the vehicle orientation (change in angle) is processed internally by the turn rate sensor (gyro sensor) integrated into the COMAND operating, display and controller unit.
The direction of travel data (forwards or backwards) is transferred to the COMAND operating, display and controller unit by the central gateway control unit over the interior CAN. The COMAND operating, display and controller unit then calculates the coupled position from the distance traveled and in consideration of the vehicle orientation and 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). The vertical angle (from the 3D gyro) and the data from the Electronic Toll Collection System (ETC) gates (dealer option) and the Vehicle Information and Communication System (VICS) beacons are taken into consideration (dealer option) for detecting the street level (overpass).
Locating errors with basic 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 cases, the deviation is automatically corrected by the navigation processor integrated in the COMAND operating, display and controller unit, provided GPS data are received.
Destination-oriented navigation function sequence
The 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 to the following speakers:
- Left front door speaker (H4/5)
- Right front door speaker (H4/6)
In vehicles with code (810) Sound system, the voice output is performed by the COMAND operating, display and controller unit via the Media Oriented System Transport (MOST) to the amplifier for sound system (N40/3) and from there to the two described speakers via direct lines.
Destination-oriented navigation function sequence through visual display
The signals for visual representation of the destination-oriented navigation (map navigation) are generated by the COMAND operating, display and controller unit and indicated on the display on the COMAND operating, display and 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 FM2/VICS signal is routed as follows:
- Antenna structure in the rear window
- Direct line
- FM rear window antenna amplifier (A2/19)
- Direct line
- Roof antenna module (A2/93)
- Direct line
- COMAND operating, display and controller unit
The VICS information is edited in the FM multiplexer integrated into the COMAND operating, display and controller unit. The information is then shown on the display on the COMAND operating, display and 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)
For dynamic route guidance, it is necessary to retrofit the VICS antenna (A2/95) (dealer option). The VICS function is integrated into the COMAND operating, display and controller unit. The VICS antenna communicates in the microwave range (2.5 GHz) with the VICS beacons installed along the road (transmission antennas). The signals received are transferred directly to the COMAND operating, display and controller unit where they are decoded. The traffic messages are stored and provided to the integrated navigation processor. The navigation processor makes the decision whether the route should be changed. If necessary, a message is output via the two described speakers saying that the route has been changed. The VICS signals are routed as follows:
- VICS antenna
- Direct line
- COMAND operating, display and controller unit
