Navigation System

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. The computer uses map information stored on a CD-ROM to determine the best route for the journey and provide the driver with details of directions and approaching junctions.

The current position of the vehicle is determined using a Global Positioning System (GPS). The GPS uses satellites which transmit radio signals to provide information about the satellite position i.e. latitude, longitude, altitude, almanac data and time.

The almanac data is the current status of the 24 satellites which orbit the earth. 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 navigation system requires the almanac data from at least four different satellites to calculate a three dimensional "fix"on its location. As the vehicle moves the computer continually up dates this information so that at all times the computer knows the precise location of the vehicle.

The direction of the vehicle is determined by the navigation computer using a solid state gyro sensor located inside the computer. The gyro sensor supplies angular acceleration data for the vehicle to the navigation computer. The computer uses this information to determine the direction of travel of the vehicle.