6
GENERAL
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The operating principle
GPS is an active destination guidance system. You can let this system guide you
to your planned destination – even on several alternative routes – if the routes to
your destination are digitally available on CD-ROM.
GPS – Global Positioning System – is able to recognise the current geographical
position of your vehicle and to guide you to the destination on calculated routes.
This is done with the help of the signals from the 24 GPS satellites, that are in an
orbit 21,000 km above the earth.
The locating principle
The measurement starts when you first switch on the ignition of your vehicle.
The first time the system is used after installation, it can take up to 20 minutes
until the current vehicle position is displayed.
Signal reception from at least four GPS satellites is necessary to determine the cur-
rent vehicle position by calculating the position according to a method from tri-
gonometry (triangulation).
Three satellites enable a two-dimensional position indication (geographic longi-
tude and latitude).
If you receive signals from four or more satellites the position can be calculated
three-dimensionally (longitude, latitude, and altitude). In this case the accuracy
of the measurement (deviation from the actual position) is within ± 100 m.
This inaccuracy is inherent to the system and is so intended by the operator of
the GPS satellites, the U.S. Department of Defence.
If you receive only signals from one or two satellites the current position of the
vehicle cannot be determined.
