GF82.61-P-2010CEA Position Finding and Destination-Oriented Navigation, Function
GF82.61-P-2010CEA Position Finding And Destination-oriented Navigation, Function
- with CODE (527) COMAND APS with single DVD drive (with navigation)
- with CODE (512) COMAND APS with DVD changer
- except CODE (498) Japan version
Function requirements, general
^ Circuit 30g ON
^ Signals from at least 3 Global Positioning System (GPS) satellites present
Position finding and destination-oriented navigation, general
The position finding function and navigation consists of the following subfunctions:
^ Function sequence for GPS position finding
^ Function sequence for basic position finding
^ Function sequence for destination-oriented navigation through voice output
^ Function sequence for dynamic route guidance
^ Function sequence for navigation with lane recommendations
Function sequence for 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 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. An important prerequisite is the synchronicity of the clocks of 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
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 shadowing, e.g. in built-up areas and in tunnels, by high buildings, by trees
The GPS signals are received by the GPS receiver integrated into the COMAND controller unit (A40/3) directly from the multifunction antenna (A28/11) or, for models 204.0/9 with 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 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.
Function sequence for basic position finding
Basic position finding runs parallel to GPS position finding. For basic position finding the COMAND control unit requires the following information:
- Wheel speeds
- Distance traveled data
- Vehicle alignment (cardinal points)
- Direction of travel data (forwards or backwards)
The wheel speeds are recorded by the following components:
- 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)
The signals from the rpm sensor are provided over the following route:
- Direct line
- Electronic Stability Program control unit (N30/4)
- Chassis CAN (CAN E)
- Front SAM control unit with fuse and relay module (N10/1)
- Interior CAN
- COMAND control unit
Information on the vehicle direction is sensed and processed internally by the turn rate sensor (gyrosensor) in the COMAND control unit.
Information on direction of travel is provided over the following route:
- Steering angel sensor (N49) (steering angle)
- Steering column module control unit (N80)
- Chassis CAN
- Front SAM control unit (also forward and backward)
- Interior CAN
- COMAND control unit
The COMAND control unit uses the distance traveled, the vehicle alignment and the direction of travel to determine the vehicle's current position (longitude and latitude).
This computation is performed approx. every t =1/s.
Location finding errors during position finding can occur by rolling backwards with c. 15 OFF (ignition switched off) or a vehicle is transported. In both cases, the deviation is corrected automatically by the navigation processor integrated into the COMAND controller unit.
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.
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 following stretches can be excluded from the route calculation in the Mode submenu of the Navi menu:
- "Avoid freeways"
- "Avoid toll roads"
- "Avoid tunnels"
- "Avoid ferries"
- "Avoid car trains"
- "Avoid toll sticker roads"
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, voice output for navigation is output via the following speakers:
- Left front door speaker (H4/1)
- Right front door speaker (H4/2)
On vehicles with code (810) Sound system the COMAND control unit transmits the audio signals via media-oriented system transport (MOST) to the sound system amplifier control unit (N40/3), which amplifies and output them over the following speakers:
- Left front door speaker
- Right front door speaker
- Center dashboard speaker (H4/27)
The signals for the visual illustration of the navigation (map navigation) are generated by the COMAND controller unit and shown accordingly in the Audio/COMAND display (A40/8) or in the instrument cluster (A1).
Function sequence for dynamic route guidance
The dynamic route guidance considers the current traffic situation. Information on the traffic situation is sent out by a specially equipped broadcasting corporation on an area-related basis via ultra-short wave. This information can be received via FM radio by means of the radio data system (RDS) or Traffic Message Channel (TMC) function. A suitable FM/RDS transmitter must be tuned in. 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.
- Antenna amplifier for rear window FM antenna(A2/19)
- FM, AM and CV antenna amplifier (A2/18) (model 204.0)
- Rear window antenna amplifier 1 (A2/71) (model 204.2/9)
The traffic data recorder decodes the traffic information and forwards it internally to the navigation processor. The navigation processor makes the decision whether the route should be changed.
As of 1.6.09 TMCPro is also available in addition to TMC. In contrast to the public service TMC, TMCPro uses additional exclusive traffic information that is recorded with an automated sensor network. The traffic data received by TMC and TMCPro may differ. Receipt of the respective traffic data is shown at the bottom right in the Audio/COMAND display with the symbol "TMCPro" or "TMC".
The voice output for dynamic route guidance is accomplished on vehicles without code (810) Sound system via the following speakers:
- Left front door speaker
- Right front door speaker
On vehicles with code (810) Sound system, the COMAND controller unit sends the audio signals via MOST to the sound system amplifier control unit (N40/3), which amplifies them and outputs them over the following speakers:
- Left front door speaker
- Right front door speaker
- Center instrument panel speaker
Function sequence for navigation with 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. 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.
The instrument cluster only displays the midnight blue arrows.
