Subaru 2009 Impreza Navigation System - Manual (Page 90)

90 Navigation
General Information
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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.