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

MODEL 204.0 /2 with CODE (525) MB Audio 50 APS radio up to model year 08/YoM 07 

MODEL 204.0 /2 with CODE (511) Audio 50 APS with DVD changer up to model year 08/YoM 07 

Function requirements 

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. An important prerequisite is the synchronicity of the clocks, the satellites and 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 

The GPS signals are received by the GPS receiver, which is integrated into the radio with auto pilot system (A2/56), directly from the multifunction antenna (A28/11). From the GPS signals, the radio with auto pilot system then calculates 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 GPS.

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 basic position finding 

Basic position finding runs parallel to GPS position finding. For basic position finding, the radio with auto pilot system requires the following information:

Basic position finding function sequence 

For basic position finding, the radio with auto pilot system requires signals from the components listed:

The radio with auto pilot system receives the wheel speed signals from the RPM sensors listed in the following way:

The data from the turn rate sensor (gyro sensor) integrated into the radio with auto pilot system is forwarded internally in the radio with auto pilot system.

The data about the direction of travel (forwards or backwards) is received by the radio with auto pilot system in the following way:

Then, in the radio with auto pilot system, the instantaneous vehicle position (degree of longitude/latitude) is calculated from the travel distance covered and taking into consideration the vehicle orientation as well as the direction of travel.

The steering angle signal is read in by the steering column module control unit (N80) via the chassis CAN to the front SAM control unit with fuse and relay module and via the interior CAN to the radio with auto pilot system.

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 cases, when the GPS data are received, the deviation is automatically corrected by the navigation processor integrated in the radio with auto pilot system.

Calibration 

Wheel calibration is necessary following a tire change. To this end, it is necessary to enter the tire size, e.g. 225/060/016 and the coding as to whether new (depth of tread approx. 5 to 10 mm) or used tires (depth of tread approx. 3 to 5 mm) have been fitted. The entry is made via STAR DIAGNOSIS or directly at the radio with auto pilot system. 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.

General information on route calculation 

Under "Own selection", the following 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 by arrow pictograms and there is an acoustic information output stating "the route is 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 signals reach the following speakers via discrete lines:

In vehicles except code (810) Sound system, the voice output takes place on discrete lines via the radio with auto pilot system to the following speakers:

The signals are generated by the radio with auto pilot system for visually depicting destination-oriented navigation (map navigation) and transmitted over a low voltage differential signaling (LVDS) line to the Audio/COMAND display (A40/8). The switch-on request for the Audio/COMAND display comes from the radio with auto pilot system via the telematics CAN.

General information on dynamic route guidance 

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.

Function sequence for dynamic route guidance 

The FM receiver in the radio with auto pilot system receives the traffic reports from the rear window antenna FM antenna amplifier (A2/19) and forwards them to the traffic data recorder in the radio with auto pilot system. The traffic reports are stored in the traffic data recorder of the radio with auto pilot system and made available to the integrated navigation processor. The voice output for dynamic route guidance is placed on the MOST 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.

IMPORTANT In vehicles except code (810) Sound system, the voice output is processed and amplified within the radio with auto pilot system. The audio signal reaches the speaker system via discrete lines.

REFER TO SYSTEM WIRING DIAGRAMS Electrical function schematic for Auto Pilot System (APS) with CODE (810) Sound system PE82.61-P-2051-99FAA
  Front central operating unit, component description A40/9 GF54.21-P-4500CW
  Cockpit central display, component description A40/8
Entry		 GF54.30-P-6100CW
  Radio/navigation unit, component description A2/56
with CODE (525) MB Audio 50 APS radio		 GF82.61-P-4111CW 
A2/56
With code (511) Audio 50 APS with DVD changer		 GF82.61-P-4111CWA 
  Audio tuner control unit, component description N40/3
with CODE (810) Sound system		 GF82.62-P-3132CWS 
  Telephone and GPS roof antenna component description A28/11 GF82.62-P-4119CW 
  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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