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 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.
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
En
208
Appendix
Appendix
Summary of Contents for AVIC-X940BT
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