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General Information■ Accuracy of the Vehicle’s Position
Area in which GPS signals cannot be received
Because the radiowave signals from the GPS satellites travel
primarily by line of sight, the navigation system might not be able to
receive the signals in the areas described below.
(If the GPS mark does not appear on the map screen, it means that
the GPS radiowave signals are not being properly received.)
(1) Inside a tunnel
(2) Inside a building
(3) Under a three-dimensional road such as a high-speed road
(4) On boulevards lined with trees
(5) Between buildings
(6) Under a cliff or in a cave
• If the GPS antenna or its surroundings are blocked by an obstacle
(including cargo), it might not be possible for the system to
receive the GPS radiowave signals.
• If multiple paths are created due to the reflection from the
buildings, a large measurement error could occur, causing the
vehicle’s mark to deviate from its actual position.
Deviation of the vehicle’s position mark
The vehicle’s position mark could deviate from its actual position
when the vehicle is being driven under the conditions listed below
or due to conditions of the GPS satellites.
If the vehicle travels on a road whose actual shape differs from that
in the map data, the vehicle’s mark could deviate from the actual
position. The correct position will eventually appear on the screen
through the correction function. If the screen does not show the
correct position for a long time, correct the current position or make
an automatic correction.
(1) The vehicle’s mark could appear on a parallel road.
(2) When the road splits into a narrow Y, the vehicle’s mark could
appear on the other fork of the Y.
(3) When the vehicle makes a right or left turn, the vehicle’s mark
could appear on one street ahead or behind.
(4) If the vehicle is transported by a means other than the vehicle’s
own power, such as on a ferry boat, the vehicle’s mark will
remain in the position it was before the transport until the
system can calculate the position through the GPS.
(5) When the vehicle is driven on a steep incline, the vehicle’s mark
could deviate from its actual position.
(6) If there are continuous gradual curves in the same direction, the
vehicle’s mark could deviate from its actual position.
(7) If the vehicle is driven in a zigzag pattern, such as through
frequent lane changes, the vehicle’s mark could deviate from its
actual position.
(8) If the vehicle is placed on a turntable , such as in a parking area,
and turned with the ignition OFF, the orientation of the vehicle’s
mark could deviate from its actual orientation. The vehicle’s
mark could also deviate even after the vehicle has exited the
parking area.
(9) The vehicle’s mark could deviate from its actual position if the
vehicle is driven on a snow-covered road or on a mountainous
road with tire chains or snow tires.
• After driving the vehicle under those conditions, perform the
same operation given in the section on "After changing tires".
(10)The vehicle’s mark could deviate from its actual position after
the tires have been replaced.
• After replacing the tires, refer to the section on "After
changing tires".
■ How the Vehicle’s Position is detected
Detecting the vehicle’s position through the GPS
GPS stands for the "Global Positioning System"; it is a system for
detecting an object’s position through the use of the satellites of the
Defense Department of the United States.
Radiowave signals from three or more satellites are received by the
navigation system, which utilizes the principle of triangulation to
detect the position in which the radiowave signals are received.
When the navigation unit is receiving the GPS radiowave signals, a
"GPS" mark will appear on the map screen.
Detecting the vehicle’s position through self-contained
navigation
Self-contained navigation is a system that detects the vehicle’s
position by calculating the vehicle’s driven distance and turning
angle though the use of various types of sensors that are mounted
on the vehicle.
Through the use of self-contained navigation, the vehicle’s position
can be detected even in an area where the GPS radiowaves signals
cannot be received.
Making corrections to the detection of the vehicle’s position
through map matching
• In map matching, the position information resulting from the
detection of the vehicle’s position and the locus of the travel of
the vehicle up to the present are constantly compared to the
shapes of the roads on the map in order to correct the vehicle’s
position mark to the most appropriate road.
• If the vehicle is driven on a road whose actual shape differs from
its map data, the vehicle’s position mark on the map could deviate
from its actual position.
Occasionally, the correction of the vehicle’s position mark to the
actual road on the map can be observed particularly after the
vehicle has turned at an intersection or has come out of a parking
area.
■ Accuracy of the Route Guidance
The conditions listed below do not indicate a malfunction.
(1) The guidance might prompt the driver to drive straight even
though the vehicle is being driven on a straight road.
(2) The directional guidance could display multiple place names.
(3) If the vehicle makes a turn at an intersection before the guided
route, the wrong type of voice guidance could be output.
(4) The guidance might not be output while the vehicle is making a
turn at an intersection.
(5) The system might not be able to search for the proper route.
(6) If there is no road to the destination or if there is only a narrow
road, the route might only indicate up to an area that is short of
the destination.
(7) The repeat search time could be long while the vehicle is being
driven at high speeds.
(8) While the system is searching again for the route, the route
indication might not appear in time for the next right or left turn.
(9) The route might not change even if a search is made again.
(10)The system might guide the driver to make a U-turn.
(11)The system might guide the driver on a road that cannot
actually be travelled (such as on a road in which entry is
prohibited).
(12)The system might not output guidance even if the vehicle is
driven in reverse on the guided route.
(13)The system might not use a local ferry boat even if it the ferry
priority is selected.
(14)If the intersection you’re being guided to is near the end of the
route search, the system might not be able to provide guidance.
(15)The route might not go on a toll road even the toll-road priority
is selected.
Similarly, a route that uses a toll road could appear on the
screen even if the toll-road priority is not selected.
(The driver may or may not be able to select the "toll-road
priority" if both toll and free roads are available.)