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Appendix
Appendix
49
En
Appendix
Positioning technology
Positioning by GPS
The Global Positioning System (GPS) uses a
network of satellites orbiting the Earth. Each of
the satellites, which orbit at a height of
68 900 000 feet (21 000 km), continually
broadcasts radio signals giving time and posi-
tion information. This ensures that signals
from at least three can be picked up from any
open area on the ground’s surface.
The accuracy of the GPS information depends
on how good the reception is. When the sig-
nals 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 dimensions,
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 larger.
When positioning by GPS is
impossible
GPS positioning is disabled if signals cannot
be received from more than two GPS satel-
lites.
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In some driving conditions, signals from GPS
satellites may not reach your vehicle. In this
case, it is impossible for the system to use
GPS positioning.
In tunnels or en-
closed parking
garages
Under elevated
roads or similar
structures
When driving
among high
buildings
When driving
through a dense
forest or tall 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 anten-
na clear.
❐ If 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 updat-
ed. In such a case, once GPS reception is re-
stored, accuracy will recover.
Conditions likely to cause noticeable
positioning errors
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 dis-
played on the map screen.
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