SEL526V
GPS (Global Positioning System)
NHEL0296S0103
GPS is the global positioning system developed and operated by
the US Department of Defense. GPS satellites (NAVSTAR) trans-
mit radio waves and orbit around the earth at an altitude of approxi-
mately 21,000 km (13,000 miles).
GPS receiver calculates the three-dimensional position of the
vehicle (latitude, longitude, and altitude from the sea level) by the
time difference of the radio wave arriving from more than four GPS
satellites (three-dimensional positioning).
When the radio wave is received from only three GPS satellites, the
two-dimensional position (latitude and longitude) is calculated,
using the altitude from the sea level data calculated by using four
GPS satellites (two-dimensional positioning).
Positioning capability is degraded in the following cases.
I
In two-dimensional positioning, when the vehicle’s altitude
from the sea level changes, the precision becomes lower.
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The location detection performance can have an error of about
100 m (300 ft) even in three-dimensional positioning with high
precision. Because the precision is influenced by the location
of GPS satellites used for positioning, the location detection
performance may drop depending on the location of GPS sat-
ellites.
I
When the radio wave from GPS satellites cannot be received,
for example, when the vehicle is in a tunnel, in a parking lot
inside building, under an elevated superhighway or near strong
power lines, the location may not be detected. Turbulent/
electric weather conditions may also affect positioning perfor-
mance. If something is placed on the antenna, the radio wave
from GPS satellites may not be received.
SEL630X
COMPONENT DESCRIPTION
NHEL0296S02
NAVI Control Unit
NHEL0296S0201
I
The gyro (angular speed sensor) and the CD-ROM drive are
built-in units that control the navigation functions.
I
Signals are received from the gyro, the vehicle speed sensor,
and the GPS antenna. Vehicle location is determined by com-
bining this data with the data contained in the CD-ROM map.
Locational information is shown on liquid crystal display panel.
CD-ROM Driver
NHEL0296S0202
Maps, traffic control regulations, and other pertinent information
can be easily red from the CD-ROM disc.
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NAVIGATION SYSTEM
System Description (Cont’d)
EL-469