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the sensor status and it may recover the
accuracy to normal condition (page 139).
Map matching
As mentioned, the positioning 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.
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 positioning by GPS is
impossible
• GPS positioning is disabled if signals
cannot be received from more than two
GPS satellites.
• 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 enclosed parking garages
Under elevated roads or similar
structures
When driving among high buildings
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