HOW DOES THE NAVIGATION SYSTEM WORK?
The navigation system is a tool to assist the driver in daily traffic. The
system allows you to enter the destination and activate ªGuidanceº, and
the system provides guidance advice through both audio and visual
advice.
Determination of the vehicle position
The movement of the vehicle is measured by sensors which are
integrated into the navigation system. The distance driven is recorded by
an electronic signal from the speedometer and the rotary movements of
turns by the gyroscope (a rotary measurement system). The information
from these sensors is, however, not always exact as the values can be
affected by tire slippage, varying tire pressure due to changes in
temperature, etc.
Data from the sensors, in conjunction with positional information
received from the global positioning system is transmitted to the
navigation computer. The resultant calculated position is then compared
against the road network data stored on the CD-ROM in order to display
the current vehicle position.
GPS (global positioning system)
The global positioning system is based on the reception of navigation
signals from a total of 24 GPS satellites at a height of 20 920 km
(13 000 miles).
Signals from at least four satellites must be received to determine the
vehicle position with sufficient accuracy. The GPS receiver can handle up
to eight satellite signals simultaneously. This allows an accuracy of
approximately 100 m (328 ft), which is further improved by other
sensors so that a final accuracy of approximately6mto18m
(20 ft to 60 ft) can be reached.
When the vehicle is parked for a long period of time, the satellites
change their orbital positions. Therefore, when the ignition is turned on
again it can take a few minutes before the navigation system can pick up
enough satellites and evaluate the received signals.
²Sufficient reception is indicated by the green symbol that appears in
the system's display. If the satellite symbol remains red, the GPS
reception is not sufficient.
Introduction
3
GLOSSARY
Map CD
Compact Disc with CD-i format. CD which contains data only readable by
a special CD player. Digitized road maps, city maps and a database of
facilities of special interest (for example parking, hotels, restaurants, gas
stations etc.) are stored on a map CD.
GPS
Global positioning system: A system for determination of the exact
position by receiving data from several earth orbiting satellites. To
calculate a precise position at least four satellites have to be receivable
simultaneously. The GPS receiver calculates the vehicle position with the
received GPS signals. The satellite icon is displayed in green color as
long as sufficient GPS data is received.
Gyroscope
One of the sensors used for calculation of the current vehicle position.
The gyro is located in the navigation computer. It measures changes in
the vehicle's direction.
Navigation computer
The core component of the navigation system. The navigation computer
compares the data on the map CD with the signals coming from the
sensors and from the GPS receiver and calculates the current vehicle
position. Also route planning and guidance functions are handled by the
navigation computer.
SDVC
Speed dependent volume control: For compensation of engine, wind and
rolling noise of the vehicle the voice volume is increased dependent on
the vehicle speed. The increase of the voice volume is controlled by the
navigation system. You can adjust the volume increments by selecting
different SDVC curves.
Glossary
39
