Navigation System: Description and Operation
Navigation System
The navigation computer generates the appropriate visual display output to support navigation functionality. This is communicated to the display unit via an RB video link for the LCD display. The navigation computer also generates the audible navigation instructions (speaker level) that are transmitted through the front channels of the stereo system speakers. The GPS receiver is an integral part of the navigation computer.
Purpose of the System
A modern satellite navigation system is an in-car guidance system that uses information transmitted from satellites orbiting the earth. From this information, the navigation computer can pinpoint the present position of the vehicle. The system computes this information against other data, which is generated in the car, and is able to calculate a route for the driver to take to reach his/her destination. The information is displayed on a monitor in the vehicle and is accompanied by computer generated audio instructions informing the driver when and where to maneuver.
The Navigation System consists of the following components:
- CD Rom Navigation Computer
- GPS Antenna
- Gyro Sensor
- Distance Sensors
- Display
System Components
CD ROM Navigation Computer
The navigation computer is located under the right front seat.
Access to the CD-ROM slot on the front of the navigation computer is from the rear
The navigation computer consists of a CD-ROM drive, the hardware for navigation computation and a gyro sensor. The navigation computer generates the appropriate visual display output to support navigation functionality. Additionally the computer will provide the HMI (Human Machine Interface) for the On Board Computer. This is communicated to the display unit via an RB video link for the LCD display. The navigation computer also generates the audible navigation instructions (speaker level) that are transmitted through the front channels of the stereo system speakers. The GPS receiver is an integral part of the navigation computer.
GPS Antenna
The GPS antenna (1) is located centrally below the dash upper at the base of the windshield.
The GPS antenna receives information from the constellation of GPS satellites in the sky. The signals are 'line of sight' transmissions i.e. there must be an unobstructed view between the satellites and the GPS antenna. The antenna is able to pick up signals through glass and non-electrically conducting trim - but not through metallic objects, buildings etc.
GPS Receiver
The GPS receiver generates and maintains the almanac. The GPS receiver determines the vehicles current position and compares it to the "dead reckoning position". The dead reckoning position is determined from the gyro-sensor and the wheel speed signal overlaid on the CD-ROM database. At any given point in time the computer can determine the vehicle's current position by reconciling the dead reckoning position with the GPS positioning.
Gyro Sensor
To provide a directional input to the system a gyro sensor is installed within the navigation computer.
Distance Sensors
The distance input to the navigation computer is a square wave output in proportion to vehicle speed from the ABS\ASC\DSC module (right hand rear wheel speed sensor). This signal is used by the Navigation Computer to match the position of the vehicle to the map.
Display
The color display is a 5.8" 16:9 aspect ratio color TFT LCD. An HMI processor integral to the navigation computer generates the display graphics for all modes of operation. The display has an RB Video input for the graphics information from the navigation computer. The frame rate (60 Hz) automatically adjusts to match the source signal. The screen frequency is controlled by a K-bus message.
Audio Mute Key
The audio mute key is used to toggle the navigation audio instructions on or off. When audio mute is active the mute LED is illuminated to inform the user.
Re-route Key
The re-route key is used to request a new route when the navigation system is providing guidance information. There is no function for this button when the navigation system is not providing guidance, although the K-bus message will always be transmitted.
Repeat Key
The repeat key is used to request the last spoken navigation message to be repeated if appropriate.
Audio Systems
The system will function in conjunction with the radio headsets. K-bus messages will provide radio muting during navigation messages. The navigation audio output will be via the radio headset unless a Digital Signal Processing amplifier is fitted.
Reverse Light Signal Input
This signal is used by the Navigation Computer to determine the direction of vehicle travel. The signal is supplied from the gearbox reverse light switch (manual versions). On the ECVT gearbox the signal is supplied from the starter inhibitor/reverse light switch.
On Board Computer (OBC)
The trip computer is displayed and operated via the LCD screen. The trip computer calculates and displays the following information:
- Trip distance
- Range
- Average fuel consumption 1
- Average fuel consumption 2
- Estimated journey time
- Average speed
- Limit
Service Mode
Selecting the SET menu item and then confirming with the rotary control knob enters Service Mode. The MENU button should then be pressed and held for eight seconds. This will display the Service Mode menu screen.
The Service Mode has five main items displayed on its menu as follows:
- On-board monitor
- NAVIGATION / GRAPHIC ELEMENT
- GPS
- Sensor check
To access the functions: turn the rotary control knob to select the desired function and then press to enter.
On-board Monitor
The ON-BOARD MONITOR VERSION information will appear as follows:
- SW level:
- HW level:
- DIAG index:
- BUS index:
- Encoding index:
- Supplier:
Selecting FUNCTIONS causes pop-up menu to appear allowing the selection of:
- VERSION - This displays the ON-BOARD MONITOR VERSION screen as described above.
- KEY FUNCTION - This allows each key, including the rotary control knob, on the display unit control panel to be checked for correct operation. Each key is allocated a letter or number, which is displayed when pressed or turned. The screen display shows FF if no key is pressed, FEH if multiple keys are pressed:
- BRIGHTNESS This enables the brightness of the display to be adjusted via a slider control on the screen that is controlled with the rotary control knob. Rotation in either direction will brighten or darken the LCD screen in a range from -10 to +10. Pressing the rotary control knob will select the chosen setting.
Access to these functions is possible using the rotary control knob.
Selecting FUNCTIONS will return to the pop-up menu or selecting
Navigation/Graphic Element
The navigation computer version information will appear as follows:
- SW level:
- HW level:
- DIAG index:
- BUS index:
- Encoding index:
- Supplier:
Select
GPS
The GPS VERSION information will appear as follows:
- Receiver Version
- Receiver SW Date
Select FUNCTIONS: A pop-up menu appears which allows the selection of:
- GPS VERSION
- GPS STATUS
- GPS TRACKING INFO
Access to these functions is possible using the rotary control knob.
Sensor Check
The display screen provides visual checks that all input sensors are operating. The following sensor status is displayed:
Wheel sensors: Wheel speed sensors used by the ABS\ASC\DSC system calculate the vehicle speed. When the vehicle is stationary the wheel speed sensor boxes will show zero. When the car is driven the values should increase in proportion to the vehicle speed. When the vehicle is driven in a straight line, the values should be similar.
GPS satellites: Displays the number of satellites visible to the system at that time.
GPS status: Displays the number of satellites visible and the GPS system status. The GPS statuses displayed are as follows: GPS Error: - There is a communication error between the GPS receiver and the navigation computer. Satellite Search: - The system is searching for satellites and may indicate a failure of the GPS system. Ensure that the GPS antenna is not covered and check harness connections between the GPS receiver and the antenna. Satellite Contact: - The system is tracking a number of satellites. This message shows that the system is functioning correctly, but there is not enough information to determine the vehicle position. Check that the GPS antenna is not covered in any way. It may take several minutes for the GPS system to locate enough satellites to determine the vehicle position. Position Known: - The system is tracking a number of satellites and has a current fix on the vehicle position. This shows that the system if functioning correctly.
Gyro: The navigation computer has a gyro which determines changes of vehicle direction. When the vehicle turns to the left, the direction icon should move anti-clockwise and the displayed value should decrease. When the vehicle turns to the right the direction icon should move clockwise and the displayed value should increase. The amount movement of the direction icon and of increase or decrease in the displayed value depends on the tightness of the turn.
Direction: The direction sensor determines whether the vehicle is traveling forward or backward. With the vehicle in any forward gear or neutral or 'park' for automatic transmission, the display will show 'Forward'. When reverse gear is engaged the display should show 'Backward'.
Selecting FUNCTIONS will return to the pop-up menu or selecting
Service Mode is exited by pressing the MENU button on the control panel which returns the system to the main navigation.
Software Loading/Configuration
All vehicles with navigation systems are delivered with the latest software installed and the language versions set to the appropriate market configuration. The system can have software loaded by the dealer, when new software is released for example. Software can be loaded from a CD that is inserted into the navigation computer. The computer automatically senses that a software CD has been inserted and will display a software loading screen on the display unit LCD or the instrument cluster message center and begin to load the software. The LCD will display that software loading has commenced and the software version. The languages being loaded will also be displayed where appropriate.
Diagnostics
The diagnostic socket allows the exchange of information between the navigation system components and DIS. The diagnostic socket is located in the driver's footwell. A dedicated diagnostic bus is connected between the socket and the instrument cluster and allows the retrieval of diagnostic information and coding of certain functions to be performed using DISplus. The instrument cluster forms the gateway for the K-bus link to the navigation components. The cluster translates diagnostic messages from DISplus into K-bus messages recognized by the navigation system components.