Pioneer CNDV-50MT - Manual (Page 114)

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quality is poor, only two dimensions, latitude and
longitude, can be obtained and positioning errors
are somewhat greater.
Positioning by dead reckoning
The 3D Hybrid Sensor in the main unit also
calculates your position. The current location 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
discrepancies 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 memory;
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 detected.
Inclination of a road can be detected.
Simple hybrid mode
When the speed pulse is not detected,
positioning is performed in this mode. Only
horizontal movement is detected, so it becomes
less accurate. Also, when the positioning by GPS
is not available, such as when your vehicle enters
a long tunnel, the discrepancy between your
actual and calculated position may become
bigger.
❒ The speed pulse data comes from the speed
sensing circuit. The location of this speed
sensing circuit depends on your vehicle
model. In some cases, it is impossible to
make a connection to it, and in such a case
we recommend that the ND-PG1 speed pulse
generator (sold separately) be used.
How do GPS and dead
reckoning work together?
For maximum accuracy, your Navigation System
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
becomes 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.
To ensure maximum accuracy, the dead
reckoning system learns with experience. By
comparing the position it estimates with your
actual position as obtained using GPS, it can
correct for various types of error, such as tyre
wear and the rolling motion of your vehicle. As
you drive, the dead reckoning system gradually
gathers more data, learns more, and the
accuracy of its estimates gradually increases. So,
after you have driven some distance, you can
expect your position as shown on the map to
show fewer errors.
❒ If you use chains on your wheels for winter
driving or put on the spare wheel, errors may
suddenly increase because of difference in
wheel diameter. The system detects the fact
that the tire diameter has changed, and
automatically replaces the value for
calculating distance.
❒ If the ND-PG1 is used or if your vehicle is
operating in Simple hybrid mode, the distance
calculation value cannot be replaced
automatically.
MAN-CNDV-50MT-EN.book Page 112 Wednesday, May 4, 2005 1:49 PM