GF82.61-P-2004TW Position Finding and Destination-Oriented Navigation

GF82.61-P-2004TW Position Finding And Destination-Oriented Navigation
- with CODE (525) MB Audio 50 APS radio


Route calculation, function
After destination input, the route is calculated and continuously updated by the navigation processor integrated into the radio control panel and navigation unit (A2/56). It can only be calculated within the digitized map area. The calculated route is a preconditio for destination-oriented navigation.
The navigation processor uses the read-in navigation CD, the entered destination, and the current position of the vehicle to calculate the route. For the computation, it takes the roads and its attributes read in by the navigation CD, such as one-way streets, bans on turns, or road categories into account.

Here, it is possible for the user to indicate how the route should be calculated:
^ Quickest route
^ Shortest route
^ Dynamic route
^ Separate selection

When selecting the "Dynamic route", a traffic data recorder integrated in the radio control panel and navigation unit is used to store traffic messages received via two-way radio and automatically taken into consideration when calculating the route. The route is then calculated with the optimum time, in a manner similar to the "Fastest route" option.

Notification that the route has been recalculated taking traffic messages into consideration, is provided. Under "Own selection", the following stretches can be blocked from the route calculation:
^ Highway
^ Ferry
^ Toll
^ Tunnel

Following the calculation of the route, the navigation processor generates a list of roads and junctions to be driven along. This list of routes is drawn on for destination-oriented navigation. It may also be displayed by calling up the "Information" menu.

Route updating
When the driver deviates from the calculated route, a new route is calculated by the navigation processor. When doing so, the current position and the direction of travel are taken into consideration.

The message "New Route" appears on the display and "NEW RTE" appears in the multifunction display (A1p13) of the instrument cluster (A1).

Trips outside the digitized map area
If the vehicle leaves the digitized map area (e.g. driving in a multilevel car park), then no route can be calculated. "OFF ROAD" appears on the display. "OFF MAP" appears upon leaving the digitized map area. The destinations that lie outside the digitized map area cannot be incorporated into the route calculation.

Bypassing traffic jams
After the traffic information radio channel has sent a traffic jam message, the user can have the system calculate a route that bypasses the traffic jam before reaching the particular stretch.

To do this, the user must press the "Bypass" button and enter the following data:
^ The length of the traffic jam, including the distance to the start of the traffic jam
^ The corresponding stretch should be blocked within the detailed list of routes.

Destination-oriented navigation, function
Destination-oriented navigation is the compilation and output of route recommendations to guide the driver to the desired destination. Destination-oriented navigation is contingent on:
^ Continuous position finding in operation (executed automatically).
^ Destination was entered
^ Route calculation done.















Continuous position finding, function
Continuous location finding means that the current position of the vehicle is calculated. It is active when the ignition is switched on (circuit 15R ON) and is carried out by the navigation processor integrated into the radio control panel and navigation unit. During the switch-on phase (software is loaded), only the basic position finding is available. After switching off the ignition (circuit 15R OFF), all the vital position finding parameters are stored for the duration of the run-on time (approx. 30 min). Continuous position finding uses 3 methods, which mutually complement each other and therefore ensure very accurate and reliable position finding:

These include:
^ Basic position finding (dead reckoning)
^ Map-based position finding
^ Global Positioning System (GPS) position finding

Manual entry of vehicle location
It is possible to enter the location manually on the radio control panel and navigation unit. In the following instances this can be useful:
^ After transporting the vehicle with a ferry or a train
^ If there had not yet been any GPS reception at the start of a journey







Basic position finding (dead reckoning) is the base function in continuous position finding. It is constantly carried out by the navigation processor of the radio control panel and navigation unit when the ignition is switched on and depends on the navigation CD that is read in. After switching the ignition off, the current position is stored in the navigation processor.

Basic position finding (dead reckoning) is used to calculate the following information:
^ Travel distance covered
^ Direction of travel (backwards or forwards)
^ Vehicle alignment

Basic position finding (dead reckoning) is performed approx. 1/s.

Distance traveled
The navigation processor integrated in the radio control panel and navigation unit receives the wheel speed signals from the ESP control unit (N47-5) via the Controller Area Network Bus class C (engine compartment) (CAN-C) . Evaluation of the wheel speed signals results in the travel distance covered.

Direction of travel
The signal for reverse travel, which is transmitted by the EIS [EZS] control unit (N73) via the Controller Area Network bus class B (interior) (CAN-B) allows the navigation processor of the radio control panel and navigation unit to recognize the direction of travel (forward or reverse).

Vehicle orientation
The navigation processor uses the data of the turn rate sensor (gyro sensor) to calculate the orientation (compass direction) of the vehicle.

Position finding errors during basic position finding (composite positioning)
Rolling backwards without the transmission being shifted into reverse gear is evaluated as moving forwards and can lead to temporary errors in location finding. Rolling when the ignition is switched off or transporting the vehicle can also distort the position finding.
In all 3 cases, the deviation is automatically corrected by the navigation processor on receipt of GPS data.

The direction of travel signal (forward, reverse) is generated by the wheel speed sensors. This enables an accurate recording of the travel distance to be made.

Calibration
Wheel calibration is necessary following a tire change. To do this, the input of tire size and the coding, whether new tires (depth of tread approx. 5 to 10 mm) or worn tires (depth of tread approx. 3 to 5 mm) have been fitted, is necessary. The values are input via STAR DIAGNOSIS or directly at the radio control panel and navigation unit. A special calibration journey is not required.

Because of the tire abrasion, 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.







The navigation processor or the radio control panel and navigation unit tracks the position of the vehicle using the read-in CD. In the event of deviations in the course traveled from the calculated route, the position coordinates of the basic location finding are corrected.

Map-based position finding is only available in the digitized area of the read-in CD. By comparing the calculated position of the vehicle with the read-in DVD, the deviation can be recognized an corrected automatically.







The GPS is a satellite-assisted localizing system that has been set up by the American Ministry of Defense. It is free and available worldwide. Various GPS satellites constantly transmit time and position data. Signals from at least 4 satellites are required for the first position calculation. Signals from 3 satellites are subsequently sufficient. The GPS position finding is, in particular, for journeys outside the digitized map area and after transportation of the vehicle (e.g. train, ferry and towing) irreplaceable. Starting GPS position finding again (following interruption of the satellite reception) may take several minutes (for initial startup of the device up to 20 min).

Every minute, approximately 50 GPS recalculations of the location take place.

Global positioning system (GPS) map matching, function
The GPS antenna (A2/49a2) receives the satellite signals and amplifies them. With the aid of these signals, the navigation processor in the radio control panel and navigation unit calculates the vehicle location and the positioning accuracy.The actual calculation is based on the measurement of the transmission times of the signals transmitted synchronously by the various satellites. An important requirement here is the synchronicity of the clocks for 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. When the navigation processor determines that basic location finding is less precise than GPS location finding, the currently calculated position is corrected with the aid of the GPS data. In addition to this the sequence of locations calculated by the GPS is used to determine the vehicle's route.

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

^ atmospheric interference,
e.g. bad weather, water vapor, fog
^ Multiple reception due to reflection of the signals,
e.g. from walls of buildings
^ Signal shading,
e.g. in built-up areas, in tunnels, through high buildings, through trees

For proper reception it is important not to have any obstacle between the GPS antenna and the satellite. Positioning accuracy lies at approx. 10 m.

Destination-oriented navigation in digitized map area, function
When traveling within the digitized map area, the following information, which is calculated by the navigation processor of the radio control panel and navigation unit, are available to the user:
^ Current position and route of the vehicle
^ List with streets and junctions to be driven
^ Distance from the destination and likely time up to arrival
^ Travel direction recommendation
^ Travel direction arrow
^ Name of current road
^ Name of the road to turn into
^ Distance to next turn-off

The type of CD is automatically recognized. The actual destination-oriented navigation is supported by the voice output.

Destination-oriented navigation in non digitized map area, function
When traveling outside the digitized map area, e.g. in multi-level car parks or on dirt roads, the navigation processor of the radio control panel and navigation unit switches over to "Destination- oriented navigation outside the digitized map area". The message "OFF ROAD" appears on the display of the radio control panel and navigation unit. Upon leaving the map limits (outside of the country) "OFF MAP" appears. Destinations outside of the digitized map area cannot be incorporated into the route calculation.

After returning to the digitized map area, the system automatically continues with "Destination-oriented navigation in digitized map area". The GPS signals can be used to determine the possible roads, on which the vehicle may be located. During this process a slight delay in the destination-oriented navigation may result.

When the message "OFF MAP" appears, the complete destination-oriented navigation can be continued after inserting a corresponding navigation CD for the foreign country.