Appendix

Appendix

Positioning technology

! In some driving conditions, signals from

Positioning by GPS

GPS satellites may not reach your vehicle.

In this case, it is impossible for the system

The Global Positioning System (GPS) uses a

to use GPS positioning.

network of satellites orbiting the Earth. Each

 

 

of the satellites, which orbit at a height of

 

 

68 900 000 feet (21 000 km), continually broad-

 

 

casts radio signals giving time and position in-

 

 

formation. This ensures that signals from at

 

 

least three can be picked up from any open

 

 

area on the ground’s surface.

In tunnels or en-

Under elevated

The accuracy of the GPS information depends

closed parking

roads or similar

 

garages

structures

on how good the reception is. When the signals are strong and reception is good, GPS can determine latitude, longitude and altitude for accurate positioning in three dimensions. But if signal quality is poor, only two dimen- sions, latitude and longitude, can be obtained and positioning errors are somewhat greater.

Handling large errors

Positioning errors are kept to a minimum by combining GPS, dead reckoning and map matching. However, in some situations, these functions may not work properly, and the error may become bigger.

When driving

When driving through

among high build-

a dense forest or tall

ings

trees

!If a car phone or cellular phone is used near the GPS antenna, GPS reception may be lost temporarily.

!Do not cover the GPS antenna with spray paint or car wax, because this may block the reception of GPS signals. Snow buildup can also degrade the signals, so keep the

antenna clear.

pIf a GPS signal has not been received for a long time, your vehicle’s actual position and the current position mark on the map may diverge considerably or may not be up- dated. In such case, once GPS reception is restored, accuracy will be recovered.

Conditions likely to cause noticeable positioning errors

When positioning by GPS is impossible

!GPS positioning is disabled if signals can- not be received from more than two GPS satellites.

For various reasons, such as the state of the road you are traveling on and the reception status of the GPS signal, the actual position of your vehicle may differ from the position displayed on the map screen.

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