Pioneer SUPERTUNERD AVIC-N5 - Manual (Page 163)

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.
To ensure maximum accuracy, the dead reck-
oning system learns with experience. By com-
paring the position it estimates with your
actual position as obtained using GPS, it can
correct for various types of error, such as tire
wear and the rolling motion of your vehicle. As
you drive, the dead reckoning system gradu-
ally 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.
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. The system detects
the fact that the tire diameter has changed,
and automatically replaces the value for
calculating distance.
p If ND-PG1 is used or if your vehicle is oper-
ating in Simple hybrid mode, the distance
calculation value cannot be replaced auto-
matically.
Map matching
As mentioned, the GPS and dead reckoning
systems used by this navigation system are
susceptible to certain errors. Their calcula-
tions may, on occasion, place you in a location
on the map where no road exists. In this situa-
tion, 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.
With map matching
Without 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.
Appendix
En
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Appendix
Appendix