GF82.61-P-2004TX Position Finding and Navigation
GF82.61-P-2004TX Position Finding And Navigation
- with CODE (527) COMAND APS (with navigation)
"Continuous position finding", function
Continuous positioning 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 (N41/1). During the switch-on phase (software is loaded), only the basic position finding is available. After switching the ignition off (circuit 15 OFF), all important positioning parameters are stored for the duration of the run-on time (approx. 30 min). Once the run-on time has ended, the COMAND operating, display and control unit (A40/3) is switched off completely.
The position map is displayed again after the final act of navigation (destination reached).
Continuous position finding uses 3 methods which supplement each other mutually and thus guarantee very accurate and reliable position finding.
These are:
^ Basic position finding (dead reckoning)
^ GPS position finding
^ Map-supported map matching
Manual entry of vehicle location
It is possible to enter the vehicle position manually in the "Navigation" menu of the COMAND operating, display and control unit (A40/3) This may be useful in the following cases:
^ Following transport of the vehicle (e.g. ferry or train)
^ If there is no GPS reception at the start of a journey
"Basic position finding", function
Basic location finding (dead reckoning) is the basic function of continuous location finding. When the ignition is switched on, it is carried out continuously by the navigation processor (N41/1) and independent of the digital versatile disk (DVD) map. The current position is stored after the ignition is switched off.
The following information is calculated with the aid of basic position finding (composite positioning):
^ Distance traveled
^ Direction of travel (forward or reverse)
^ Vehicle orientation
The basic position finding (composite positioning) is performed approximately every 1 s.
Distance traveled
The navigation processor (N41/1) receives the wheel speed signals from the ESP control unit (N47-5) via the class C (engine compartment) Controller Area Network bus (CAN-C) . These wheel speed signals are evaluated to determine the distance traveled.
Direction of travel
Using the signal for wheel rotational direction, which is sent by the ESP control unit (N47-5) and transmitted by the central gateway control unit (N93) to the Controller Area Network bus class B (interior) (CAN-B), the navigation processor (N41/1) detects the direction of travel (forward or reverse).
Vehicle orientation
From the data of the yaw rate sensor (gyro sensor) and the sequence of the locations calculated using GPS, the navigation processor (N41/1) calculates the orientation (compass direction) of the vehicle.
The difference in the calculated mileage and the mileage actually covered between 2 turnoff points is used to automatically recalibrate the tire circumference (necessary due to tire wear).
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 both cases the deviation is corrected automatically by the navigation processor (N41/1) upon receipt of the GPS data.
The driving direction signal (forward or reverse) is generated by the wheel speed sensors, thus enabling accurate registration of the mileage.
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 entry is accomplished with Star Diagnosis or directly at the COMAND operating, display and control unit (A40/3). A special calibration drive is not required.
"Position finding through GPS", function
The GPS is a satellite-supported localizing system set up by the American Department of Defense. It is a toll-free service available throughout the world. Various GPS satellites constantly transmit time and position data. 4 satellites are needed for the first position calculation, then 3 receivable satellites are sufficient. GPS position finding is irreplaceable for journeys outside the digitized map area and after vehicle transport (e.g. train or ferry journeys and towing) A new GPS location (after interruption of the satellite reception) can take several minutes (up to 20 minutes when it is first put into operation )
Every minute, approximately 50 GPS recalculations of the position take place.
The navigation processor (A41/1) calculates the location of the vehicle and the accuracy of positioning from the satellite signals received and amplified by the GPS antenna (A2/49a2).
The actual calculation is based on the measurement of the transmission times of the signals transmitted synchronously by the various satellites. Here, an important prerequisite is that the satellite and receiver clocks are synchronized . For this purpose, the receiver has an automatic time correction feature which is possible with the aid of the satellite signals. If the navigation processor (N41/1) determines that the basic position finding is less precise than the GPS position finding, the currently calculated position is corrected using the GPS data. In addition, the vehicle's course of travel is determined with the aid of the sequence of the locations calculated with GPS.
Possible interference when receiving GPS signals
As GPS operates in the gigahertz (GHz) range (microwaves) and the signals are weak, reception interference may occur due to:
^ 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, tunnels, through high buildings, through trees
GPS reception therefore necessitates a clear view of the sky. Positioning accuracy is approx. 100 m.
"Map-based position finding", function
The position of the vehicle is constantly tracked on the DVD map by the navigation processor (N41/1). In the event of deviations in the course traveled from the calculated route, the position coordinates of the basic position finding (composite positioning) are corrected.
Map-supported location finding is only available in the digitized area of the DVD map. By comparison with the calculated position of the vehicle with the DVD map, the deviation can be recognized and corrected automatically.
"Route calculation", function
The route is calculated and constantly updated by the navigation processor (N41/1) after the destination input on the COMAND operating, display and control unit (A40/3). This can only be calculated within the digitalized map areas. The calculated route is the prerequisite of the destination guidance system. The navigation processor (N41/1) calculates the route using the DVD map data, the input destination, and the current position of the vehicle. For the calculation it takes into account roads and their attributes read from the DVD map, such as one-way streets, turn prohibitions, road classes, etc. (where available). Here, it is possible for the user to indicate how the route should be calculated:
^ Fastest route
^ Shortest route
^ Dynamic route
^ Own selection
When "dynamic route" is selected, traffic messages received over radio (ultra-short wave (FM) or network operator) are stored in the traffic data recorder integrated into the navigation processor (N41/1) and automatically taken into consideration in 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:
^ Freeway
^ Ferry
^ Toll road
^ Tunnel
The roads which are liable to tolls are marked in color on the map.
The navigation processor (N41/1) creates a list of the streets and junctions to be driven to after the route has been calculated. This route list is used for destination guidance. It may also be displayed by calling up the "Information" menu.
Route updating
If the driver deviates from the calculated route, a new route list is calculated by the navigation processor (N41/1). When doing so, the current position and the direction of travel are taken into consideration. The message "New Route" appears on the display of the COMAND operating, display and control unit (A40/3) and "NEW RTE" appears on the instrument cluster (A1).
Trips outside the digitized map area
If the vehicle leaves the digitized DVD map area (e.g. driving into a multilevel car park), then no route can be calculated or updated. "OFF ROAD" appears on the display of the COMAND operating, display and control unit (A40/3). Upon leaving the map boundary (e.g. foreign country), the message "OFF MAP" appears.
Destinations which lie outside of the digitalized map area cannot be taken into consideration on calculation of the route.
Bypassing traffic tailbacks through the "Detour" function
After a tailback message via traffic radio and before the route section concerned is reached, a route calculation can be arranged which bypasses the tailback. 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 must be blocked within the detailed route list.
"Navigation", function
Destination guidance is the generation and output of driving recommendations, in order to guide the driver to the desired destination. The prerequisites of destination guidance include:
^ Continuous position finding in operation (takes place automatically).
^ Destination was entered
^ Route has been calculated.
The navigation processor (N41/1) constantly compares the route calculation data with the data from constant position finding.The measures for further route guidance are derived from this. Depending on the position of the vehicle, a distinction can be made between the following 2 navigation modes:
^ Destination within digitized DVD map area
^ Navigation in non-digitized DVD map area
"Navigation in digitized map area", function
In the case of journeys within the digitized map area, the following information, which is calculated by the navigation processor (N41/1), is available to the user:
The current route and position of the vehicle on a digital map
^ Route list
^ Distance from the destination and likely driving time up to arrival
^ Direction recommendation
^ Arrow indicating the driving direction
^ Name of the road currently being traveled along
^ Name of the road to turn into
^ Distance from the next junction (specified in units of length or as a bar graph)
For destination guidance, 3 illustration modes are possible:
^ with map
^ with map and symbol display before turn-off points
^ With symbol display (route control symbols)
The scale of the map can be changed in stages (50 m/cm to 500 km/cm on the screen). Moreover, it is possible to select whether the map is aligned in the direction of travel (forward) or t the North (facing North).
Blaupunkt Travelpilot DX navigation DVD
Separate one-way lanes (fine geometry) are automatically displayed with this DVD.
The DVD type (with the latest fine geometry) is automatically detected and the graphic displayed in a second optimized set of line thickness.The voice output supplements the actual navigation.
"Navigation in non-digitized map area", function
On journeys outside the digitized map area (e.g. company grounds, etc.) but still within the DVD map limits, the navigation processor (N41/1) switches over to "navigation in non-digitized map area".
The following message appears on the COMAND operating, display and control unit (A40/3) display:
^ "OFF ROAD"
In addition if the vehicle is outside the DVD map limits (outside the country), the following message appears:
^ "OFF MAP"
When entering the OFF-ROAD mode, the map and a route information is shown on the display of the COMAND operating, display and control unit (A40/3).
In both cases only basic position finding (dead reckoning) with correction by GPS data takes place
Limited destination guidance takes place while only specifying:
^ Distance to the destination as the crow flies
^ the direction to the destination (as arrow)
After reentering the digitized map area, the system automatically continues with "Destination guidance in digitized map area" . The GPS position is used to help determine the roads on which the vehicle could be located. During this process a slight delay in the route guidance may result.
In the event of the message "OFF MAP", comprehensive navigation can be continued after loading a corresponding abroad DVD.
