Pioneer AVIC-X3-II - Manual (Page 147)

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
21 000 km, 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 3D Hybrid 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 Gyrosensor and inclination of the
road with the G sensor.
The 3D Hybrid Sensor can even calculate
changes of altitude, and corrects for discre-
pancies in the distance travelled caused by
driving along winding roads or up slopes.
Also, the navigation system learns the driving
conditions and stores information in the mem-
ory. Thus, as you drive more, the precision of
the positioning becomes more accurate.
The method of positioning changes as follows
depending on whether the speed pulse of your
vehicle is detected or not:
3D hybrid mode
This is active when the speed pulse is de-
tected. Inclination of a road can be detected.
Simple hybrid mode
When the speed pulse is not detected, posi-
tioning is performed in this mode. Only hori-
zontal movement is detected, so it becomes
less accurate. Also, when the positioning by
GPS is not available, such as when your vehi-
cle enters a long tunnel, the discrepancy be-
tween your actual and calculated position may
become bigger.
p The speed pulse data comes from the
speed sensing circuit. The location of this
speed sensing circuit depends on your ve-
hicle model. In some cases, it is impossible
to make a connection to it, and in such a
case we recommend that ND-PG1 speed
pulse generator (sold separately) be used.
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 3D Hybrid Sensor. However, if only the data
from the 3D Hybrid Sensor is available for a
long period, positioning errors are gradually
compounded until the estimated position be-
comes unreliable. For this reason, whenever
GPS signals are available, they are matched
with the data of the 3D Hybrid Sensor and
used to correct it for improved accuracy.
Appendix
Engb
147
Appendix
Appendix