GF82.61-P-2010TXB Position Finding and Destination-Oriented Navigation, Function
GF82.61-P-2010TXB Position Finding And Destination-oriented Navigation, Function
- with CODE (512) COMAND APS with DVD changer
- with CODE (527) COMAND APS with single DVD drive (with navigation)
- with CODE (528) COMAND with DVD changer
General information
The position finding and destination-oriented navigation function is divided into the following subareas:
^ General Global Positioning System (GPS) position finding
^ GPS position finding function sequence
^ General information on basic position finding
^ Basic position finding function sequence
^ Recalibration
^ General information on route calculation
^ Destination-oriented navigation function sequence through voice output
^ General information concerning dynamic route guidance, except code 494 USA version
^ Function sequence for dynamic route guidance, except code 494 USA version
^ Destination-oriented navigation through driving lane recommendations
^ Map function
Function requirements
^ Status "Circuit 30 ON"
^ The COMAND operating, display and controller unit (A40/3) is operating fault-free
General information concerning GPS position finding
The GPS is a satellite-based positioning system. It is available worldwide. The GPS satellites permanently transmit time an 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). The accuracy of the position finding and the actual calculation is essentially based on the measurement of the runtimes of the signals transmitted synchronously by the various satellites. A vital precondition is the synchronicity of the clocks in the satellites and in the receiver. To this end the receiver is equipped with an automatic time correction, which in turn is made possible with the aid of the satellite signals.
GPS position finding function requirements
^ No error in GPS antenna system
Function sequence for GPS position finding
The GPS signals are received by the GPS receiver integrated in the COMAND operating, display and controller unit via the following path:
- GPS antenna (A2/49a2)
- Direct line
- GPS antenna splitter (A2/5), with code 359 TELE AID emergency call system, and direct line
The GPS signals are used by the COMAND operating, display and controller unit to calculate the momentary position of the vehicle. In addition, the vehicle's direction of travel is determined with the aid of the sequence of the locations calculated with GPS.
Possible interference in reception of GPS signals: 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
- Multi-path reception due to signal reflections, e.g. from building walls
- Signal blocking, e.g. in built-over areas and in tunnels, through high-rise buildings, trees
General information concerning basic position finding
Basic position finding runs parallel to GPS position finding. The COMAND operating, display and controller unit requires the following information for basic position finding:
- Wheel speed signals
- Distance traveled data
- Vehicle alignment (cardinal points)
- Data for direction of travel (forward or reverse)
Basic position finding function requirements
^ Proper communication with ESP control unit (N47-5)
Basic position finding function sequence
For basic position finding the COMAND operating, display and controller unit requires signals from the following components:
- Left front rpm sensor (L6/1), right front rpm sensor (L6/2), left rear rpm sensor (L6/3), right rear rpm sensor (L6/4) for measuring wheel speed signals
- ESP control unit
- Turn rate sensor (gyro sensor), integrated into the COMAND operating, display and controller unit for determining the vehicle alignment (direction)
- Central gateway control unit (N93), for capturing data on direction of travel
The COMAND operating, display and controller unit receives the wheel speed signals from the listed rpm sensors in the following way:
- Direct line
- ESP control unit
- Controller Area Network bus Class C (engine compartment) (CAN-C)
- Central gateway control unit (N93)
- Controller area network bus, class B (interior compartment) (CAN B)
The data in the turn rate sensor (gyro sensor) integrated into the COMAND operating, display and controller unit is forwarded within the COMAND operating, display and controller unit.
The data about the direction of travel (forward or backward) is received by the COMAND operating, display and controller unit in the following way:
- Central gateway control unit
- CAN-B
After this, the COMAND operating, display and controller unit uses the distance traveled, the vehicle alignment and direction of travel as well as the previous location to calculate the instantaneous vehicle position (longitude and latitude).
The steering angle signal is read in from the steering column tube module (N80) and relayed via CAN-C to the central gateway control unit and via CAN-B to the COMAND operating, display and controller unit.
The basic position finding calculation is carried out approx. once per second.
Locating 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 cases, the deviation is corrected automatically by the navigation processor integrated into the COMAND operating, display and controller unit.
Recalibration
Because of the tire abrasion, a constant recalibration of the tire circumference is required. It is carried out automatically and uses the difference between the calculated and actually traveled distance between 2 turning points calculated with the aid of map-based position finding.
General information on route calculation
The following stretches can be removed from the route calculation under "Navi":
- Freeways, except code 494 USA version
- Freeways, with code 494 USA version
- Ferries
- Tunnels
For vehicles except code 494 USA version, additional stretches can be excluded from the route calculation:
- Toll road
- Roads requiring toll stickers
- Car trains
Route calculation is accomplished using the options set to the best possible extent. If observance of the options is not possible, then the options set are ignored for the sections in question and a message is displayed and signaled audibly.
The set criteria and options can be displayed and changed at any time. After successful calculation, the route is displayed on the map and the information is relayed acoustically
- "Route calculated".
Function sequence for destination-oriented navigation 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 voice output for destination-oriented navigation is sent directly (without code 810 Sound system) or via the Media Oriented System Transport (MOST) and the sound system amplifier (N40/3) (with code 810 Sound system) to the following speakers:
- Left front door speaker group (H4/1)
- Right front door speaker group (H4/2)
- Center cockpit speaker (centerfill) (H4/27)
The signals for visually displaying navigation (map navigation) are generated by the COMAND operating, display and controller unit and shown on the display on the COMAND operating, display and controller unit as well as in the instrument cluster (A1) in the form of arrow pictographs.
General information concerning dynamic route guidance, except code 494 USA version
The current traffic situation is taken into consideration in the dynamic route guidance. The incoming information concerning the traffic situation can be received by the radio data system (RDS)/ Traffic Message Channel (TMC) function via frequency modulation (FM) radio. Information on the current traffic situation is broadcast regionally by specially equipped radio stations via ultra-short wave (FM). A suitable FM/RDS transmitter must be tuned in. The traffic data recorder decodes the traffic information and forwards it internally 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 should be changed is output via the vehicle speaker.
Function sequence for dynamic route guidance, except code 494 USA version
The FM receiver in the COMAND operating, display and controller unit receives the traffic messages from:
^ the left antenna amplifier module (A2/64) (model 211.0, model 219) or
^ the left antenna amplifier module and the right antenna amplifier module (A2/65) (model 211.2)
and relays them to the traffic data recorder in the COMAND operating, display and controller unit. The traffic reports are stored in the traffic data recorder of the COMAND operating, display and controller unit and made available to the integrated navigation processor. The voice output to the dynamic route guidance is sent to the speakers directly, without Code 810 Sound system, or via the sound system amplifier control unit, with code 810 Sound system.
Destination-oriented navigation through driving lane recommendations
For certain turnoff situations on multiple-lane exit points (e.g. freeway intersections), driving lane recommendations are shown in the bottom line.
Along with a turnoff recommendation, the distance to the actual turnoff point is also displayed by means of a bar graph. The lanes have arrows assigned to them, which indicate on which lane the destination can be reached or the best way to reach it.
The following colors apply for representation on the display of the COMAND operating, display and controller unit:
Midnight blue: The best or recommended lane.
Light blue: The lane is correct, but a lane change will soon be required.
Gray: This lane will not take you to the destination.
The instrument cluster only displays the midnight blue arrows.
Map function
The map display is always controlled by the COMAND operating, display and controller unit.
