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Position finding and destination-oriented navigation, function - GF82.61-P-2010CW

MODEL 204.0 with CODE (527) COMAND APS with single DVD drive (with navigation) up to Model Year 8 

MODEL 204.0 with CODE (512) COMAND APS with DVD changer up to Model Year 8 

MODEL 204.2 with CODE (527) COMAND APS with single DVD drive (with navigation) up to Model Year 8 

MODEL 204.2 with CODE (512) COMAND APS with DVD changer up to Model Year 8 

Function requirements for Global Positioning System (GPS) position finding 

The position finding and destination-oriented navigation function is divided into the following subareas:

General information on GPS position finding 

The GPS is a satellite-based positioning system. It 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). 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.

Function sequence for GPS position finding 

GPS signals are received by the GPS receiver integrated into the COMAND controller unit (A40/3), directly from the multifunction antenna (A28/11). The GPS signals are used by the COMAND controller 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.

General information on basic position finding 

Basic position finding runs parallel to GPS position finding. For basic position finding the COMAND controller unit requires the following information:

Basic position finding function sequence 

For basic position finding, the COMAND controller unit requires signals from the following components:

The wheel speed signals are received by the COMAND controller unit from the listed RPM sensors in the following way:

The turn rate sensor (gyro sensor) data in the COMAND controller unit are forwarded within the COMAND controller unit.

The data about the direction of travel (forwards or backwards) is received by the COMAND controller unit in the following way:

After this the COMAND controller unit uses the distance traveled, the vehicle alignment and the direction of travel to calculate the vehicle position (degree of longitude and degree of latitude) at any given time.

The steering angle signal is read in by the control unit for the steering column module (N80), and forwarded over the chassis CAN to the front SAM control unit with fuse and relay module and over the interior CAN to the COMAND controller unit.

IMPORTANT Calculation of the basic position finding takes approx. 1/s.

IMPORTANTError 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.

Calibration 

Wheel calibration is necessary following a tire change. To this end, the tire size, and coding, whether new (tread depth approx. 5 to 10 mm) or used tires (tread depth approx. 3 to 5 mm) are mounted have to be entered. The entry is made using STAR DIAGNOSIS or directly on the COMAND controller unit. A special calibration journey is not required.

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.

IMPORTANTPossible 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:

General information on route calculation 

Under "Own selection", the following stretches can be excluded from the route calculation:

For vehicles except code (494) USA version, additional stretches can be excluded from the route calculation:

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 a successful calculation, the route is displayed on the map and this information is then 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 placed on the Media Oriented System Transport (MOST) and then amplified in the sound system amplifier control unit (N40/3) (with code (810) Sound system). The audio signal reaches the following speakers over discrete lines.

For vehicles except code (810) Sound system, voice output takes place directly over the COMAND controller unit through discrete lines at the following speakers:

The signals for destination-oriented navigation visual display (map navigation) are generated by the COMAND controller unit and forwarded over a low voltage differential signaling (LVDS) line to the Audio/COMAND display (A40/8). The Audio/COMAND display switch-on request is generated by the COMAND controller unit over the telematics CAN.

General information on dynamic route guidance (for vehicles except code (494) USA version) 

The current traffic situation is taken into consideration in the dynamic route guidance. The incoming information on the traffic situation can be received by the radio data system/Traffic Message Channel (RDS/ TMC) function via FM radio. The information on the current traffic situation is sent out by a specially equipped broadcasting corporation on an area-related basis via 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 (for vehicles except code (494) USA version) 

The FM receiver in the COMAND controller unit receives the traffic messages from the antenna amplifier for the rear window FM antenna (A2/19) and forwards them to the traffic data recorder in the COMAND controller unit. The traffic messages are stored in the traffic data recorder of the COMAND controller unit and made available to the integrated navigation processor. The voice output for dynamic route guidance is placed on the MOST ring and then amplified in the sound system amplifier control unit (with code (810) Sound system). The audio signal reaches the speaker system via discrete lines.

Destination-oriented navigation through driving lane recommendations 

For certain turnoff situations on multiple-land exit points (e.g. freeway intersection) 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 are valid for representation on the Audio/COMAND display:

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.

IMPORTANT The instrument cluster (A1) only displays the midnight blue arrows.

Map function 

Map display is always controlled by the COMAND controller unit. The following display functions are supported:

REFER TO SYSTEM WIRING DIAGRAMS Electrical function diagram for navigation system With code (512) COMAND APS with DVD changer
with CODE (494) USA version
With code (359) TELE AID emergency call system
with CODE (810) Sound system		 PE82.85-P-2051-99FAA
With code (512) COMAND APS with DVD changer
With code (527) COMAND APS with Single DVD disk drive (with navigation) with CODE (810) Sound system Except code (494) USA version		 PE82.85-P-2051-99FAB
  Front central operating unit, component description A40/9 GF54.21-P-4500CW
  Cockpit central display, component description A40/8
High		 GF54.30-P-6100CWH
  COMAND controller unit, component description A40/3
With code (527) COMAND APS with Single DVD disk drive (with navigation)		 GF82.85-P-3136CW
A40/3
With code (512) COMAND APS with DVD changer		 GF82.85-P-3136CWA
  Telephone and GPS roof antenna component description A28/11 GF82.62-P-4119CW 
  GPS antenna splitter, component description A2/5
Model 204.0
With code (512) COMAND APS with DVD changer
With code (359) TELE AID emergency call system		 GF82.62-P-3129CWU 
  Speaker system, component description H4/1, H4/2, H4/3, H4/4, H4/27 Except code (810) Sound system GF82.62-P-4220CW 
H4/1, H4/2, H4/3, H4/4, H4/27, H4/29, H4/54, H4/57 with CODE (810) Sound system GF82.62-P-4220CWS 
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