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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
21000km, continually broadcasts radio sig-
nals giving time and position information. This
ensures that signals from at least three can be
picked up from any open area on the earth’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 dimen-
sions, latitude and longitude, can be obtained
and positioning errors are somewhat greater.
Positioning by dead reckoning
The built-in sensor in the navigation system
also calculates your position. The current loca-
tion is measured by detecting driving distance
with the speed pulse, the turning direction
with the gyro sensor and inclination of the
road with the G sensor.
The built-in sensor can even calculate
changes of altitude, and correct the discrepan-
cies in the distance traveled caused by driving
along winding roads or up slopes.
If you use this navigation system with connect-
ing the speed pulse, the system will become
more accurate than no connection of speed
pulse. So you connect the speed pulse without
fail to get the accuracy of positioning.
p The position of the speed detection circuit
vary depending on the vehicle model. For
details, consult your authorized Pioneer
dealer or an installation professional.
p Some types of vehicles may not output a
speed signal while driving at just a few kilo-
meters per hour. In such a case, the current
location of your vehicle may not be dis-
played correctly while in traffic congestion
or in a parking lot.
How do GPS and dead
reckoning work together?
For maximum accuracy, your navigation sys-
tem continually compares GPS data with your
estimated position as calculated from the data
of built-in sensor. However, if only the data
from the built-in sensor is available for a long
period, positioning errors are gradually com-
pounded until the estimated position becomes
unreliable. For this reason, whenever GPS sig-
nals are available, they are matched with the
data of the built-in sensor and used to correct
it for improved accuracy.
p If you use chains on your wheels for winter
driving or put on the spare wheel, errors
may suddenly increase because of differ-
ence in wheel diameter. Initialize the sensor
status and it may recover the accuracy to
normal condition.
= For details, refer to Clearing status on
page 149.
En
198
Appendix
Appendix