Pioneer CNDV-50MT - Manual (Page 66)

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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 if you put on the spare wheel, the
errors may appear to suddenly increase
because of the increased wheel diameter. The
system detects the fact that the tyre 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.
Map matching
As mentioned, the GPS and dead reckoning
systems used by this Navigation System are
susceptible to certain errors. Their calculations
may, on occasion, place you in a location on the
map where no road exists. In this situation, the
processing system understands that vehicles
travel only on roads, and can correct your
position by adjusting it to a nearby road. This is
called map matching.
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 bigger.
When the positioning by GPS is
impossible
• If signals cannot be received from more than
two GPS satellites, GPS positioning does not
take place.
• 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.
With map matching
Without map matching
MAN-CNDV-50MTP-EN.book Page 64 Friday, April 29, 2005 10:33 AM