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

GF82.61-P-2010CA Position Finding and Destination-Oriented Navigation, Function
MODEL 207.3 /4
- with CODE (525) MB Audio 50 APS radio
- with CODE (511) Audio 50 APS with DVD changer

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 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. 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, 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.

Function sequence for 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:
- 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) (without code (233) DISTRONIC PLUS) or the Premium Electronic Stability Program control unit (N30/7) (with code (233) DISTRONIC PLUS).
- Chassis CAN (CAN E)
- Front SAM control unit with fuse and relay module (N10/1)
- Interior CAN (CAN B)
- Radio with auto pilot system
Information on the vehicle direction is sensed and processed internally by the turn rate sensor (gyro sensor) in the radio with auto-pilot system.
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
- Radio with auto pilot system
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 performed approx. every t =1/s.
Location-finding 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.
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 door tweeter (H4/1h1)
- Left door bass speaker (H4/1h2)
- Right door tweeter (H4/2h1)
- Right door bass speaker (H4/2h2)
On vehicles with code (810) Sound system, the radio with auto-pilot system transmits the audio signals via the media-oriented system transport (MOST) to the sound system amplifier control unit (N40/3), which amplifies and output them over the following speakers:
- Door tweeter
- Door bass speaker
- Center dashboard speaker (H4/27)
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 (A40/8) or the instrument cluster (A1) accordingly.

Function sequence for dynamic route guidance
Dynamic route guidance is performed in the "Dynamic route" or "Eco route" mode (as of 1.6.2010). The dynamic route guidance considers the current traffic situation. This information on the traffic situation can be received via FM radio by means of the radio data system (RDS) or Traffic Message Channel (TMC) function. The traffic information is sent out by a specially equipped broadcasting corporation on an area-related basis via ultra-short wave. A suitable FM/RDS transmitter must be tuned in.
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 FM receiver in the radio with auto-pilot system receives the traffic messages from the following antenna amplifiers and relays them to the traffic data memory in the radio with auto-pilot system:
- FM 1, AM and CL [ZV] antenna amplifier (A2/18) (model 207.3) or FM 1, AM and CL [ZV] antenna amplifier (A255) (model 207.4)
- Rear window FM antenna antenna amplifier (A2/19) (model 207.3) or TV 3, FM2 and DAB band III (A2/54) antenna amplifier (model 207.4)
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.
The voice output for dynamic route guidance is accomplished on vehicles without code (810) Sound system via the following speakers:
- Door tweeter
- Door bass speaker
For vehicles with code (810) Sound system, the radio with auto pilot system transmits the audio signals via the Media Oriented System Transport (MOST) to the sound system amplifier control unit, which amplifies the signals and outputs them over the following speakers:
- Door tweeter
- Door bass speaker
- Center instrument panel speaker