Navigation System: Description and Operation

Navigation System

Introduction To The Global Positioning System (GPS)

The system used to calculate the current position of the vehicle is called the GPS (global positioning system). The system utilizes satellites which are owned by the United States Department of Defense (DoD). A total of 24 satellites orbit the earth every 12 hours at a height of 20,000 km (12500 miles), and between 5 and 11 of these satellites can be seen from a single point at any given time. The orbits are tilted to the earth's equator by 55 degrees to ensure coverage of polar regions. Each satellite transmits radio signals to provide information about the satellite position i.e. latitude, longitude, altitude, almanac data and an accurate time signal generated by an on-board atomic clock. Each satellite contains four atomic clocks.

The vehicle needs to receive data from at least four different satellites to give a three dimensional fix on its current position.

As the vehicle moves, this information is continually being updated. The computer determines which satellites are 'visible' to the system and their current position and relationship to each other. Using this information the computer can account for positional deviations of the satellites and compensate to enhance the accuracy of the navigation system.

The GPS (global positioning system) signal is also known as the Precision Positioning Signal (PPS).

PPS predictable accuracy is:
^ 22 meters horizontal accuracy
^ 27.7 meters vertical accuracy
^ 200 nanoseconds time accuracy.

Each navigation system provides computer generated audible and visual route guidance information to enable the driver to reach a desired destination. The system allows the driver to choose the desired route using minor or major roads or highways and the quickest or shortest route. Directions to hospitals, museums, monuments and hotels are also available. The computer uses map information stored on a CD (compact disc) -ROM to determine the best route for the journey and provide the driver with details of directions and approaching junctions.

Navigation System Component Location

Navigation System Component Location:

Navigation System Control Diagram





Navigation System Component Location with VICS (Japan only)

Navigation System Component Location with VICS (Japan only):

Navigation System Control Diagram with VICS (Japan only)





The navigation system comprises the following components:
^ Touch Screen Display (TSD)
^ Navigation computer
^ GPS (global positioning system) antenna

In addition to the standard navigation system it is possible in certain markets to add:
^ Traffic Message Channel (TMC) system
^ Vehicle Information and Communication System (VICS, Japan only)

Touch Screen Display





The Touch Screen Display (TSD) is located in the center of the instrument panel. The TSD is a touch sensitive 7 inch LCD (liquid crystal display) VGA screen containing 800 x 480 pixels in a 15:9 format. The TSD is connected to the infotainment system on the Media Oriented Systems Transport (MOST) ring. The MOST ring is a fibre optic communications data bus that allows high speed transfer of control instructions and audio around the system.

The TSD processes its own video for system operation but receives the navigation graphics from the navigation computer on a dedicated serial link called GVIF (Gigabit Video Interface).

TSD Harness Connector No C2819 Pin Out Table





TSD Harness Connector No C2820 Pin Out Table





TSD Harness Connector No C2823 Pin Out Table





TSD Harness Connector No C2825 Pin Out Table





Navigation Computer





The navigation computer is located under the front LH seat.

The navigation computer is a DVD (digital versatile disc) based system to allow for a greater capacity of data to be stored. This means that map discs can now carry far more information than the previous CD (compact disc) based discs. For example there is now one map disc for Europe where previous CD (compact disc) based systems have required different discs for each country. The navigation computer also carries the GPS (global positioning system) receiver and the voice recognition software.

The navigation computer is connected to the TSD by a private CAN (controller area network) bus and a dedicated GVIF (Gigabit Video Interface). The GVIF carries all the video information to the TSD, while the CAN (controller area network) bus is used for data and control instructions to and from the TSD.

Navigation Computer Harness Connector No C2114 Pin Out Table





Navigation Computer Harness Connector No C2113 Pin Out Table





GPS (global positioning system) Antenna





The GPS (global positioning system) antenna is located in a pod which is located in the center of the vehicle roof at the rear. The GPS (global positioning system) antenna is connected to the GPS (global positioning system) computer by a single co-axial cable and passes signals from the GPS (global positioning system) satellites to the navigation computers built in receiver for processing.

It is possible for the GPS (global positioning system) antenna to lose the signal from the GPS (global positioning system) satellites:
^ In hilly or tree lined areas
^ Built up areas with tall buildings
^ In multi store car parks
^ In garages
^ In tunnels
^ In bridges
^ During heavy rain or thunderstorms.

When the signal is lost the navigation computer will continue to give guidance using memory mapped data from the DVD (digital versatile disc) map until the signal is restored.

Traffic Message Channel (TMC) Receiver





The Traffic Message Channel (TMC) receiver is located in the rear RH (right-hand) side of the luggage compartment. The TMC receiver is connected to the MOST ring and transmits TMC data to the navigation computer (via the TSD). The navigation computer then displays this information on the TSD and also re-routes the navigation guidance around any traffic hold ups. The TMC data is received via the FM (frequency modulation) antenna located in the rear screen via an antenna amplifier located above the rear tailgate spoiler.

TMC is available in many European markets.

Vehicle Information and Communication System (VICS Japan only) Receiver
The VICS system comprises the following components:
^ VICS receiver
^ VICS beacon antenna
^ VICS RF antenna





The VICS receiver is located behind the instrument panel between the heater assembly and the in-vehicle crossbeam. The VICS receiver is connected to the navigation computer via a dedicated link.

The VICS receiver, receives information from the beacon antenna in the center of the instrument panel and the VICS antenna located in the rear screen element.

VICS Beacon Antenna





The VICS beacon antenna is located on top of the instrument panel. The antenna receives infra red and RF signals from road side transmitters.

Navigation System Operation

The navigation system receives GPS (global positioning system) information via the GPS (global positioning system) antenna. The GPS (global positioning system) signals are used by the navigation computer to calculate the vehicles position. Once the driver has input a desired destination the navigation computer can calculate a route, based on the drivers pre-determined preferences or the default settings in the navigation computer.

The navigation system is accessed by pressing the navigation button at the bottom left hand side of the TSD. The driver will then have the option of on road navigation or off road navigation.

On Road Navigation
On road navigation is initiated by the driver inputting a destination. This can be achieved by:
^ Entering in an address using the TSD.
^ Entering a post code.
^ Choosing a pre-entered address from the address book.
^ Choosing a point of interest from the map disc database.

The driver is then guided to the destination by a scrolling map display and voice guidance. The display can be varied by scale and display type.

Off Road Navigation
The off road navigation route comprises a series of way points which are followed sequentially. Direct point to point guidance is given to the first way point in the route. When the vehicle arrives at the first way point guidance is given to the second way point in the route. This process continues for subsequent way points until the final way point (destination) is reached.

The routes are stored in the non-volatile memory of the navigation computer.

The routes can be entered on the TSD and comprise way points, longitude and latitude destination and previously stored routes.

The different route guidance screens give the user the information required for direct point to point direction to the selected destination (guidance mode). The same guidance screens are also available even when guidance is not being given (compass mode). Not all the destination and guidance information is shown on the guidance screens when in compass mode. I this instance the route title is COMPASS MODE.

4x4 I
4x4i gives the driver additional information regarding the following vehicle systems:
^ Suspension travel Gear selected
^ Range selected
^ Terrain response
^ Vehicle heading
^ Compass heading
^ Steering wheel angle.

The 4x4i System uses inputs from other vehicle systems to display information about suspension and transmission operation along with navigational information.

Traffic Message Channel (TMC) System
The Traffic Message Channel (TMC) is a function of the FM (frequency modulation) Radio Data System (RDS). The system broadcasts real-time traffic and weather information. Data messages are received and decoded by the TMC receiver and passed onto the navigation system, which then delivers them via the navigation system interface. TMC messages are filtered by the navigation computer so that only those relevant to the current journey are displayed, allowing the navigation system to offer dynamic route guidance - alerting the driver of a problem on the planned route and calculating an alternative route to avoid the incident.

TMC traffic information systems conform to a global standard that has been adopted by traffic data gatherers, information service providers, broadcasters and vehicle/receiver manufacturers. TMC information is received via the normal FM (frequency modulation) radio antenna.

All TMC receivers use the same list of event codes, while the location database (on the map disc) contains both a country-specific set of location codes for the strategic European road network

TMC traffic data is currently broadcast in many European countries.

Vehicle Information And Communication System (VICS, Japan only)
The VICS system supplies the navigation computer with information to enable the navigation computer to re-route the navigation guidance or to inform the vehicle driver of traffic conditions in the vehicles vicinity. Information is provided to the system through three routes:
^ RF transmission
^ Infra-red transmission
^ FM (frequency modulation) multiplex transmissions.

The information is passed to the navigation computer via the VICS receiver and the IHU

RF Transmission
RF transmission is generally transmitted from road side beacons mainly on expressways. The information transmitted is:
^ Traffic congestion
^ Travel time to next intersection
^ Traffic conditions in surrounding areas and expressway turn offs
^ Traffic accidents
^ Speed limits
^ Lane regulations
^ Tire change
^ Parking availability at expressway service areas and parking areas.

The RF transmissions are received by the beacon antenna mounted on the top of the instrument panel.

Infra-Red Transmission
Infra-Red transmissions are transmitted from road side beacons on major trunk roads. The information transmitted is:
^ Traffic congestion and travel time
^ Traffic accidents
^ Breakdowns
^ Road works restrictions
^ Parking availability.

FM (frequency modulation) transmissions
FM (frequency modulation) transmissions are broadcast as part of the normal RDS FM (frequency modulation) transmission. Information transmitted is:
^ Traffic congestion and travel time for wide areas
^ Traffic accidents, road works, speed limits and lane restrictions for a wide area
^ Parking availability information.

Diagnostics
The TSD and the navigation computer both have built in self tests that allow the technician to diagnose fault conditions. Fault codes and diagnostics can also be achieved via T4.

TSD Diagnostics
The TSD has in built diagnostics to aid the diagnosis of system faults. The diagnostics allow the technician to interrogate the following:
^ Hard key function
^ Touch screen function
^ Video input
^ RGB video
^ Vehicle signals
^ Self test
^ Configurations
^ Vehicle configurations
^ MOST ring function.

The built in diagnostics are accessed as follows:
^ Once the system is powered up enter the 'Home' menu page.
^ Press and hold the TSD in the center at the top of the screen for approximately 5 seconds and then press the navigation hard key.
^ A 'Diag PIN Entry' box will appear' Type in the access code 753.
^ Once this code has been accepted the Diagnostic Menu screen will be displayed.

Hard Key Test Screen
The hard key test is used to determine the function of the two switches integrated into the TSD. Pressing either of the buttons will turn the corresponding icon on the screen green if it is functioning correctly.

Touch Screen Test Screen
Entering the Touch screen test screen allows the technician to test the physical side of the touch screen. The technician can choose between checking the screen integrity and re-calibrating the screen. Using the Touch Switch Check button will display a blank screen. Touching the screen in any place will give a series of co-ordinates. If a faulty area of the screen is touched the co-ordinates will not display.

Re-calibrating the screen allows the technician to align the touch screen co-ordinates to the pressing of the screen. This is achieved by pressing a series of on screen targets as they are displayed.

Vehicle Signals
The vehicle signals screen displays inputs from other vehicle systems to the TSD. These signals include:
^ Battery voltage
^ Lights (on or off)
^ Graphic illumination dimming duty
^ Output audio allocation
^ PCB temp
^ Speed inhibit (on or off)
^ MOST Fibre Optic Transceiver (FOT) temperature
^ Parking brake position (electric park brake on or off)
^ Backlight PWM (pulse width modulation) duty
^ Beep volume
^ Beep tone.

Video Input Test
This screen will allow the testing of video inputs that are connected to the TSD. This includes TV/DVD (digital versatile disc) Rear Seat Entertainment (RSE) and television.

RGB Color Test
This function allows the technician to test the colors generated by the TSD. A second screen displays six solid colors, selecting the color will fill the screen with the chosen color and pressing the TSD again will revert back to the color test screen.

Self Test
The self test function displays any fault codes that are present for the TSD. The screen also displays the current state of the ignition switch and the battery voltage.

Two additional buttons in the screen allow the technician to clear the fault codes and to test the TSD.

Configurations
The configurations screen displays information about the TSD and the navigation computer. Switching between the two components is achieved via the soft key at the top LH corner of the screen.

The information contained in the screens is as follow:
^ Vehicle type
^ Component serial number
^ Component part number
^ Component part level
^ CPU/bootloader lever
^ Main CPU application version
^ Sub CPU software version
^ Private CAN (controller area network) database version.

Vehicle Configurations
Selecting the vehicle configurations option allows the technician to inspect the components fitted to the vehicle entertainment system. There are four screens which can be navigated through via the next and previous buttons.

MOST Test
The MOST test screen displays information about the MOST signals being sent around the MOST ring. Using any part of the audio system will bring up the MOST message on the screen. This can be used to help diagnose MOST related faults.

Navigation Computer Diagnostics
The navigation computer has in built diagnostics to aid the diagnosis of system faults. The diagnostics allow the technician to interrogate the following:
^ Navigation info
^ Parts info
^ Manual check
^ Self check.

Each area has sub level of menus to access further information. The built in diagnostics are accessed as follows:
^ Once the system is powered up enter the navigation system via the navigation hard key.
^ Agree to the disclaimer screen.
^ Enter the navigation home menu.
^ Press and hold the TSD in the center at the top of the screen.
^ A 'Diag PIN Entry' box will appear, type in the access code 753.

Once this code has been accepted the on screen diagnostics menu will be displayed. The menu has the following options:
^ Navigation info
^ Manual check
^ Parts info
^ Self check.

Navigation Info
The navigation info menu has three sub menus:
^ Vehicle signals
^ GPS (global positioning system) information
^ Reset position.

Parts Info
Parts info displays information on the system component and software versions.

Manual Check
The manual check menu enables the technician to complete the following self tests:
^ Navi RGB screen test
^ Microphone input level test
^ Voice output test.

Self Check
Self check runs an internal check on the navigation computer and displays any fault codes on the TSD.

Navigation System DTC (diagnostic trouble code)