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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".
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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.)
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