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General Information
Mechanism of Detecting the Vehicle's Position
Detecting the vehicle's position through the GPS
* GPS stands for the "Global Positioning System"; it is a system for detecting the position
through the use of the satellites of the Defence Department of the United States.
Radiowave signals from three or more satellites are received by the system, which utilizes
the principle of triangulation, in order to detect the position in which the radiowave
signals are received.
When this 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 in which the GPS radiowaves signals cannot be received.
Marking 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 the map data, the
vehicle's position mark on the map could deviate from the 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 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, a
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 treed boulevards or in the mountain groves
(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 the actual position.
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