Navigation 99
General Information
■Accuracy of vehicle 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 system such as for high speed
roads
(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 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 posi-tion. The correct position will eventually appear on the screen
through the correction function. If the screen does not show the cor-
rect position for an excessively 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 means other than the vehicle's
own power, such as on a ferryboat, the vehicle's mark will
remain in the position it was before the transport until the sys-
tem 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 fre-
quent 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 vehicle's mark could devi-
ate 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 using tire chains or snow tires on a snow-cov-
ered road or on a mountainous road.
100 Navigation
General Information
(10) The vehicle's mark could deviate from its actual position after
the tires have been replaced.
(11) While driving on a public road, if an expressway that is under
construction travels over the public road, the position mark of
the vehicle may be indicated on a different road.
(12) If other electronic devices are installed on the instrument panel,
these devices may adversely affect the GPS signal communica-
tion and the position of the vehicle may not be indicated cor-
rectly.
■How the vehicle position is detected
Detecting the vehicle's position through the GPS
GPS stands for "Global Positioning System", which is a system used for
detecting an object's position through the use of satellites of the U.S.
Department of Defense.
Radiowave signals from three or more satellites are received by the
navigation system, which utilizes the principle of triangulation to
detect the position at 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 naviga-
tion
Self-contained navigation is a system that detects the vehicle's posi-
tion 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 radiowave 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
shape 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 devi-
ate 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 exited from 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 outputted.
(4) The guidance might not be outputted while the vehicle is mak-
ing a turn at an intersection.
(5) The system might not be able to search for the proper route.
