2009 INFINITI QX56 display

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INFINITI QX56 2009 Factory Service Manual AV-14
< FUNCTION DIAGNOSIS >[AUDIO SYSTEM]
NAVIGATION SYSTEM
MAP–MATCHING
Map–matching is a function that repositions the vehicle on the road
map when a new location is judged to be the most accur

AV-14
< FUNCTION DIAGNOSIS >[AUDIO SYSTEM]
NAVIGATION SYSTEM
MAP–MATCHING
Map–matching is a function that repositions the vehicle on the road
map when a new location is judged to be the most accurate. This is
done by comparing the current vehicle position, calculated by the
method described in the position detection principle, with the road
map data around the vehicle, read from the map data stored on the
HDD.
Therefore, the vehicle position may not be corrected after the vehicle
is driven over a certain distance or time in which GPS information is
hard to receive. In this case, the current-location mark on the display
must be corrected manually.
CAUTION:
The road map data is based on data stored on the HDD.
• In map-matching, alternative rout
es to reach the destination will be
shown and prioritized, after the road on which the vehicle is cur-
rently driven has been judged and the current-location mark has
been repositioned.
If there is an error in distance and/or direction, the alternative
routes will be shown in different order of priority, and the wrong
road can be avoided.
If two roads are running in parallel, they are of the same priority.
Therefore, the current-location mark may appear on either of them
alternately, depending on maneuvering of the steering wheel and
configuration of the road.
• Map-matching does not function correctly when the road on which the vehicle is driving is new and not recorded on the HDD, or when
the road pattern stored in the m ap data and the actual road pattern
are different due to repair.
When driving on a road not present in the map, the map-matching
function may find another road and position the current-location
mark on it. Then, when the correct road is detected, the current-
location mark may leap to it.
• Effective range for comparing the vehicle position and travel direc-
tion calculated by the distance and direction with the road data
read from the HDD is limited. Therefore, when there is an exces-
sive gap between the current vehicle position and the position on
the map, correction by map-matching is not possible.
GPS (GLOBAL POSITIONING SYSTEM)
GPS (Global Positioning System) has been developed and con-
trolled by the US Department of Defense. The system utilizes GPS
satellite (NAVSTAR), sending out radio waves while flying on an orbit
around the earth at the height of approx. 21,000 km (13,000 miles).
The GPS receiver calculates the vehicle's position in three dimen-
sions (latitude/longitude/altitude) according to the time lag of the
radio waves received from four or more GPS satellites (three-dimen-
sional positioning). If radio waves were received only from three
GPS satellites, the GPS receiver calculates the vehicle's position in
two dimensions (latitude/longitude), utilizing the altitude data calcu-
lated previously by using radio wa ves from four or more GPS satel-
lites (two-dimensional positioning).
Type Advantage Disadvantage
Gyroscope (angular velocity sensor) • Can detect the vehicle's turning angle quite
accurately. • Direction errors may accumulate when the ve-
hicle is driven for long distances without stop-
ping.
GPS antenna (GPS information) • Can detect the vehicle's travel direction
(North/South/East/West). • Correct direction cannot be detected when the
vehicle speed is low.
SEL685V
SEL686V
ALNIA0839GB
SEL526V
Revision: December 20092009 QX56