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Navigation mode, function - GF82.85-P-2012FQ

MODEL 218 up to model year 2013 with CODE 511 (Audio 50 APS with DVD changer) 

MODEL 218 up to model year 2013 with CODE 525 (MB Audio 50 APS radio) 

Fig 1: Navigation Mode Block Diagram
G10083330Courtesy of MERCEDES-BENZ USA

Function requirements for navigation mode in general 

General navigation mode 

The navigation system makes it possible to determine the location of the vehicle, the direction and the distance to the destination after entering the following information in the "Destination" submenu:

Apart from this, the auto pilot system (APS) also allows the route from the vehicle's location to the chosen destination to be navigated.

Navigation takes place in the form of a 2D map display on the Audio/COMAND display as well as acoustically via the vehicle's speaker system.

The route is calculated in accordance with the options set. If it should not be possible to adhere to the options, then the configured options are ignored for the stretch in question and a corresponding message is output visually as well as acoustically.

The set criteria and options can be displayed and changed at any time. Once the route has been successfully calculated, the route is then shown with the aid of arrow pictograms.

If the vehicle is no longer moving on the precalculated route, the route is recalculated. If the recalculated values are plausible for the navigation system, then the modified route is displayed.

The radio with auto pilot system is operated using the following controls or systems:

The control signals for the multifunction steering wheel button groups are read in by the radio with auto pilot system as follows:

Pressing the buttons on the radio with auto pilot system is processed internally.

The control signals for the Audio/COMAND control panel are read in by the radio with auto pilot system via the telematics CAN.

Control signals via the voice control system are picked up by the hands-free system microphone which is read in directly by the radio with auto pilot system.

Navigation, function sequence 

The information for reaching the destination (route guidance) is calculated via the navigation system integrated into the radio with auto pilot system using the data entered.

To this end, the navigation system is equipped with the following functions, which are described in the following subfunctions:

Position finding, function 

The position finding function consists of the following subfunctions:

GPS position finding function sequence 

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 t = 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.

Since GPS operates in the gigahertz (GHz) range (microwaves) and the signals are weak, reception interference can occur as a result of the following events:

The GPS signals are received by the GPS receiver, which is integrated into the radio with auto pilot system, directly from the multifunction antenna. From the GPS signals, the radio with auto pilot system then calculates the current position of the vehicle (receiver). The vehicle's direction of travel is also determined using the sequence of GPS calculated locations.

At the same time, the positioning data is compared against the map data on the navigation system DVD. On vehicles without CODE 511 (Audio 50 APS with DVD changer), it is therefore not possible to play music data media in the DVD drive when the navigation system is active.

On vehicles with CODE 511 (Audio 50 APS with DVD changer), the navigation DVD is inserted into changer slot no. 6. The user thus has five free changer slots to enable DVD data media to be played for audio entertainment purposes.

Basic position finding function sequence 

The basic position finding runs at the same time as the GPS position finding process and is a requirement for a reliable navigation if the GPS signal drops out, for example while driving through a tunnel. For basic position finding, the radio with auto pilot system requires the following information:

The radio with auto pilot system receives the wheel speeds and the wheel rotation direction from the Electronic Stability Program control unit (except model 218.374 and without CODE 233 (DISTRONIC PLUS)) or from the Premium Electronic Stability Program control unit (on model 218.374 and with CODE 233 (DISTRONIC PLUS)) via the following route:

Information on the vehicle direction is detected and processed internally by the gyro sensor in the radio with auto pilot system.

Information on direction of travel is provided in the following manner:

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.

This computation is conducted at an interval of approx. t =1 s.

IMPORTANT Location errors during position finding may occur due to rolling backwards with "Circuit 15 OFF" (ignition switched off) or when transporting the vehicle. In both cases, the deviation is automatically corrected by the navigation processor integrated in the radio with auto pilot system.

IMPORTANT The calibration following a tire replacement is performed automatically. 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 turning points calculated with the aid of map-based position finding.

Destination-oriented navigation, function 

The route guidance partial function is comprised of the following subfunctions:

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 following stretches can be excluded from the route calculation in the Mode submenu of the Navi menu:

The route is calculated in accordance with the options set. If it should not be possible to adhere to the options, then the configured options are ignored for the stretch in question and a corresponding message is output visually as well as acoustically.

The set criteria and options can be displayed and changed at any time.

After a successful route calculation, the route is displayed by arrow pictograms and there is an acoustic message output stating "the route is calculated".

On vehicles without CODE 810 (Sound system), the radio with auto pilot system forwards the voice output for route guidance to the speaker system.

On vehicles with CODE 810 (Sound system), the radio with auto pilot system transmits the voice output via the Media Oriented System Transport (MOST) to the sound system amplifier control unit, which amplifies the audio signals and outputs them via the speaker system.

IMPORTANT More detailed information on the speaker system is available in the "Speaker output function" information.

IMPORTANT The voice output of the navigation system takes place in the selected system language.

The signals for visually displaying the destination-oriented navigation (map navigation) are generated by the radio with auto pilot system and displayed on the Audio/COMAND display or the instrument cluster accordingly.

To do this, the radio with auto pilot system transmits appropriate information via an LVDS line to the Audio/COMAND display and via the interior CAN to the instrument cluster.

Function sequence for dynamic route guidance 

The dynamic route guidance considers the current traffic situation. Information on the traffic situation is received by the radio data system (RDS) or Traffic Message Channel (TMC) function via FM radio and transmitted for the respective region by a specially equipped radio broadcaster via FM.

The FM receiver in the radio with auto pilot system receives the traffic messages from the following antenna amplifiers:

The FM receiver in the radio with auto pilot system forwards the traffic messages internally to the traffic data recorder in the radio with auto pilot system. The traffic data recorder decodes the traffic information and forwards it internally to the navigation processor. The decision as to whether to change the route is made by the navigation processor.

Electrical function schematic for navigation system function PE82.61-P-2056-97XAA
Overview of system components, telematics GF82.85-P-9999FQ 
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