Pioneer AVIC-X3-II - Manual (Page 148)

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 tyre
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 tyre diameter has chan-
ged, 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.
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.
In tunnels or en-
closed parking
garages Under elevated
roads or similar
structures
Appendix
Engb
148
Appendix