Pioneer AVIC-X3 - Manual (Page 130)

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Hybrid Sensor and used to correct it for improved
accuracy.
To ensure maximum accuracy, the dead reckon-
ing 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 tyre diameter has changed, and auto-
matically replaces the value for calculating
distance.
❒ If the ND-PG1 is used or if your vehicle is oper-
ating in Simple hybrid mode, the distance cal-
culation value cannot be replaced
automatically.
Map matching
As mentioned, the GPS and dead reckoning sys-
tems used by this navigation system are suscepti-
ble 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 posi-
tion by adjusting it to a nearby road. This is called
map matching.
Handling Large Errors
Positioning errors are kept to a minimum by com-
bining 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
In tunnels or enclosed parking garages
Under elevated roads or similar structures
MAN-AVIC-X3-EN.book Page 128 Wednesday, June 6, 2007 10:15 AM