GF82.61-P-2010CAA Position Finding and Destination-Oriented Navigation, Function

GF82.61-P-2010CAA Position Finding and Destination-Oriented Navigation, Function
MODEL 207.3 /4
- with CODE (527) COMAND APS with single DVD drive (with navigation)
- except CODE (498) Japan version
MODEL 207.3 /4
- with CODE (512) COMAND APS with DVD changer

Function requirements for position finding and navigation
^ Circuit 30g ON
^ Signals from at least 3 Global Positioning System (GPS) satellites present.

Position finding and destination-oriented navigation, general
The position finding and destination-oriented navigation function is divided into the following subareas:
^ Function sequence for GPS position finding
^ Function sequence for basic position finding
^ Function sequence for calibration
^ General information on route calculation
^ Function sequence for destination-oriented navigation through voice output
^ Function sequence for dynamic route guidance (without code (494) USA version)
^ Destination-oriented navigation through driving lane recommendations
^ Map function

Function sequence for 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 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.
The GPS signals are received by the GPS receiver integrated in the COMAND controller unit directly from the multifunction antenna (A28/11) or, for vehicles with code (512) COMAND APS with DVD changer and code (359) TELE AID emergency call system, by the multifunction antenna via the global positioning system antenna splitter (A2/5). The GPS signals are used by the COMAND control 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.
Since GPS operates in the gigahertz range (microwave) and the signals are weak, reception interference can occur as the 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 shadowing, e.g. in built-up areas and in tunnels, by high buildings, by trees

Function sequence for basic position finding
Basic position finding runs parallel to GPS position finding. For basic position finding the COMAND controller unit requires the following information:
- Wheel speed signals
- Distance traveled data
- Vehicle alignment (cardinal points)
- The data for the direction of travel (forward or reverse)
For basic position finding, the COMAND controller unit requires signals from the following components:
- Wheel speeds provided by the Electronic Stability Program control unit (N30/4) (without code (233) DISTRONIC PLUS) or the Electronic Stability Program Premium control unit (N30/7) (with code (233) DISTRONIC PLUS):
- Left front axle rpm sensor (L6/1)
- Right front axle rpm sensor (L6/2)
- Left rear axle rpm sensor (L6/3)
- Right rear axle rpm sensor (L6/4)
- Turn rate sensor (gyro sensor), integrated in the COMAND controller unit, for determining the vehicle orientation (compass direction)
- Front SAM control unit with fuse and relay module (N10/1), for detecting data about the direction of travel
- Steering angle sensor (N49), for detecting the steering angle signals
The data of the turn rate sensor (gyro sensor) integrated into the COMAND controller unit is forwarded within the COMAND controller unit. The wheel speed signals are received by the COMAND controller unit from the listed rpm sensors via the following route:
- Direct line
- Electronic Stability Program control unit (except code (233) DISTRONIC PLUS) or Premium Electronic Stability Program control unit (with code (233) DISTRONIC PLUS)
- Chassis CAN (CAN E)
- Front SAM control unit
- Interior CAN (CAN B)
The data about the direction of travel (forwards or backwards) is received by the COMAND controller unit via the following route:
- Front SAM control unit
- Interior CAN
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 steering column tube module control unit (N80) and forwarded via the chassis CAN to the front SAM control unit and from there via the interior CAN to the COMAND controller unit.
The basic position finding calculation is performed approx. once per second.
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 instances the deviation is automatically corrected by the COMAND controller unit's integrated navigation processor upon reception of GPS data.

Function sequence for calibration
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 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:
- Freeways
- Toll roads
- Tunnel
- Ferries
- Car trains
- Toll sticker roads (without code (494) USA version)
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).
On vehicles with code (810) Sound system, the audio signals are output by the COMAND controller unit over the MOST to the sound system amplifier control unit and from there, to the following speakers via direct lines:
- Left door tweeter (H4/1h1)
- Left door bass speaker (H4/1h2)
- Right door tweeter (H4/2h1)
- Right door bass speaker (H4/2h2)
- Center dashboard speaker (H4/27)
On vehicles without code (810) Sound system, the audio signals are output over direct lines by the COMAND controller unit to the following speakers:
- Left door tweeter
- Left door bass speaker
- Right door tweeter
- Right door bass speaker
The signals for visual display of the navigation (map navigation) are generated by the COMAND controller unit and transmitted to the Audio/COMAND display (A40/8) via a low voltage differential signaling (LVDS) line. The Audio/COMAND display switch-on request is generated by the COMAND controller unit via the telematics CAN (CAN A).

Function sequence for dynamic route guidance (without code (494) USA version)
Dynamic route guidance is performed in the "Dynamic route" or "Eco route" mode (as of 1.6.2010). 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 (RDS) or the Traffic Message Channel (TMC) via FM radio.
In the "Eco route" mode (as of 1.6.2010), a combination of ecological and economic factors is also taken into account during navigation in addition to the current traffic situation.
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 information on the current traffic situation 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.
The FM receiver in the COMAND controller unit receives the traffic messages from the following antenna amplifiers and transfers them to the traffic data recorder in the COMAND controller unit.
Model 207.3:
- FM, AM and CL [ZV] antenna amplifier (A2/18)
- Antenna amplifier for rear window FM antenna (A2/19)
Model 207.4:
- FM, AM and CL [ZV] antenna amplifier (A2/55)
- TV 3, FM2 and DAB band III antenna amplifier (A2/54)
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 and then amplified in the sound system amplifier control unit (with code (810) Sound system).
On vehicles with code (810) Sound system, the audio signals are output by the COMAND controller unit over the MOST to the sound system amplifier control unit and from there, to the following speakers via direct lines:
- Left door tweeter
- Left door bass speaker
- Right door tweeter
- Right door bass speaker
- Center instrument panel speaker
On vehicles without code (810) Sound system, the audio signals are output over direct lines by the COMAND controller unit to the following speakers:
- Left door tweeter
- Left door bass speaker
- Right door tweeter
- Right door bass speaker

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. In addition, when a turnoff recommendation is given, 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. With day design, the following colors are valid for representation in the Audio/COMAND display:
- Midnight blue: The best or recommended lane.
- Light blue: The lane is correct but another lane change will soon be required.
- Gray: The lane will not take you to the destination.
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:
- Destination-oriented navigation map
- Positioning map
- Route map
- Scrollable map
- Destination entry map
The following map alignments can be selected:
- Northerly orientation
- Driving direction
- Bird's eye view
- "3-D map" (as of 1.6.2010)
With the "3-D map" (as of 1.6.2010), buildings in cities and mountains will be shown three-dimensionally.
As of 1.6.2010, the permissible speed will be shown at the bottom left of the map on vehicles with code (513) Speed Limit Assist.