Operating principle
The navigation system provides audible and visual route guidance information to enable the driver to reach a desired destination. The system allows the driver to differentiate the route recommendations according to his or her own personal preferences. Directions to hospitals, museums, monuments and hotels are also available. The navigation computer then integrates this data with the information from the SD card in order to optimise the route recommendation and provide the driver with up-to-date routing information.
The system used to calculate the current position of the vehicle is called the Global Positioning System (GPS). The system utilises satellites which are owned by the United States Department of Defense. A total of 24 satellites orbit the earth every 12 hours at a height of 20,000 km (12,500 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's position, for example the latitude, longitude, altitude, almanac data and an accurate time signal generated by an on-board atomic clock. Each satellite contains four atomic clocks. Each GPS satellite transmits its encoded signal towards the earth using the civilian frequency of 1575.42 MHz. The signal contains information concerning the satellite's position and the time when the signal was transmitted. The signals transmitted from the satellites reach the earth at almost the speed of light and are received by the GPS antenna.
As the various satellites are at different distances from the ground location, the vehicle's position on the ground is determined on the basis of the transmission time of the signals. This is done by the vehicle's navigation computer, which performs a comparison (correlation) of the different signals.
The vehicle needs to receive data from at least four different satellites to give a three dimensional fix on its current position. Three satellites are required to determine the position of the GPS receiver (within the vehicle) and the fourth signal is used to calculate the distance (altitude) between the ground position and the satellites.
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 Global Positioning System (GPS) signal is also known as the Precision Positioning Signal (PPS). PPS predictable accuracy is:
- 22 metres horizontal accuracy
- 27.7 metres vertical accuracy
- 200 nanoseconds time accuracy
The navigation systems are connected to the medium-speed CAN bus and work with an internal amplifier with direct outputs to the system loudspeakers. They are available with a simple CD player.
The navigation system receives GPS information from the GPS antenna. The GPS data is used by the navigation computer to calculate the vehicle's position. Once the driver has entered a destination, the navigation computer can calculate a route based on the driver's pre-determined preferences or the default settings in the navigation computer.
Navigation system
Navigation system with a dedicated 5-inch TFT colour display with a resolution of 440 x 200 pixels. Thanks to the new dual tuner system, TMC data can be received independently of the received station.
The navigation data is delivered to the customer on SD card and on CD. The navigation data on the SD card is used during normal operation; the CD serves as a data backup. Navigation maps can be copied from CD to SD card in the unit via the SD card slot. The map data is encoded after copying and can only be read in the specific unit. Before removing an SD card, it must be logged off from the audio system.
The so-called corridor navigation feature allows routes to be read in from a CD or SD card and the medium to be removed.
It is then possible to play back audio files from a CD or SD card during navigation. SD HC cards up to 32 GB can be read.
The navigation system is always supplied in combination with the Level 3 instrument cluster. A 6-CD changer is offered for the system; if selected, this changer is installed under the passenger seat.
The message centre shows the navigation system's direction arrows just like the navigation display.
Entering the keycode
The navigation system is protected against theft using a keycode.
The keycode is a 4-digit numerical code that is derived from the serial number of the system during production and is stored in the flash memory. It cannot be changed by the user.
The keycode mechanism is disabled as standard in new units and must be enabled using the Ford diagnostic unit. Once enabled, the keycode mechanism cannot be disabled again.
Following three failed attempts to enter the keycode, the operator must leave the ignition key in the Ignition ON position for an hour to acquire three new entry attempts.
