L322 Range Rover System Description and Operation
ENTERTAINMENT AND INFORMATION SYSTEMS
86-8-48 DESCRIPTION AND OPERATION
New Range Rover Navigation System
Introduction To The Global Positioning System (GPS)
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 Defence (DoD). A total of 24 satellites
circular 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 signal is also known as the Precision positioning signal (PPS). This is now the only GPS signal available,
since the Selective positioning signal (a deliberately degraded signal) was turned of on the 2nd May 2000. The
ensures that everyone can now use the higher accuracy available with PPS
SPS predictable accuracy was:
l
100 metres horizontal accuracy
l
156 metres vertical accuracy
l
340 nanoseconds time accuracy.
PPS predictable accuracy is :
l
22 metres horizontal accuracy
l
27.7 metres vertical accuracy
l
200 nanosecond 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 motorways 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-ROM to determine the best route for the journey
and provide the driver with details of directions and approaching junctions.
The system uses almanac data to determine the vehicles position. 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.
New Range Rover Navigation System
New Range Rover navigation system provides on road navigation capabilities. On road navigation requires a CD
based map to be inserted in the navigation computer. One map disc is supplied with the vehicle, subsequent updated
discs can be obtained from Land Rover dealer-ships at additional cost. Discs are available for different countries and
if road navigation is required whilst travelling abroad map discs will need to be changed for appropriate discs.
Navigation System Components
New Range Rover Satellite navigation system comprises the following components (except Japan):
l
Multi-Function Display
l
Navigation computer
l
GPS (Global Positioning System) antenna.
