NAVIGATION SYSTEM
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In map-matching, alternative routes to reach the destination will
be shown and prioritized, after the road on which the vehicle is
currently driven has been judged and the current-location mark
has been repositioned.
If there is an error in distance and/or direction, the alternative
routes will be shown in different order of priority, and the wrong
road can be avoided.
If two roads are running in parallel, they are of the same priority.
Therefore, the current-location mark may appear on either of
them alternately, depending on maneuvering of the steering
wheel and configuration of the road.
Map-matching does not function correctly when the road on
which the vehicle is driving is new and not recorded in the map
DVD-ROM, or when the road pattern stored in the map data and
the actual road pattern are different due to repair.
When driving on a road not present in the map, the map-match-
ing function may find another road and position the current-loca-
tion mark on it. Then, when the correct road is detected, the
current-location mark may leap to it.
Effective range for comparing the vehicle position and travel
direction calculated by the distance and direction with the road
data read from the map DVD-ROM is limited. Therefore, when
there is an excessive gap between the current vehicle position
and the position on the map, correction by map-matching is not possible.
GPS (GLOBAL POSITIONING SYSTEM)
GPS (Global Positioning System) has been developed and con-
trolled by the US Department of Defense. The system utilizes GPS
satellite (NAVSTAR), sending out radio waves while flying on an orbit
around the earth at the height of approx. 21,000 km(13,000 miles).
The GPS receiver calculates the vehicle's position in three dimen-
sions (latitude/longitude/altitude) according to the time lag of the
radio waves received from four or more GPS satellites (three-dimen-
sional positioning). If radio waves were received only from three
GPS satellites, the GPS receiver calculates the vehicle's position in
two dimensions (latitude/longitude), utilizing the altitude data calcu-
lated previously by using radio waves from four or more GPS satel-
lites (two-dimensional positioning).
Accuracy of the GPS will deteriorate under the following conditions.
In two-dimensional positioning, the GPS accuracy will deteriorate when the altitude of the vehicle position
changes.
There may be an error of approximately 10 m (30 ft.) in position detected by three-dimensional position-
ing, which is more accurate than two-dimensional positioning. The accuracy can be even lower depending
on the arrangement of the GPS satellites utilized for the positioning.
Position detection is not possible when the vehicle is in an area where radio waves from the GPS satellite
do not reach, such as in a tunnel, parking lot in a building, and under an elevated highway. Radio waves
from the GPS satellites may not be received when some object is located over the GPS antenna.
Position correction by GPS is not available while the vehicle is stopped.
SEL686V
SKIA0613E
SEL526V
