GPS Measurement   1-8
GPS Measurement
GPSGPS is the acronym for Global Positioning System.
The MMCS uses GPS satellites that orbit the Earth 
in space at an altitude of approximately 20,000km. 
Electromagnetic waves from at least three of these 
satellites are received on the Earth by the system, 
making it possible to learn the current position.
Map MatchingWhen traveling with just the GPS, there may be errors 
in the current position display. In such case, “map 
matching” is the function that compensates for this 
error by assuming that vehicles travel on roads and 
placing the current position on a nearby road.
GPS antenna positionThe position of the vehicle is determined from the 
weak electromagnetic waves from GPS satellites 
received by the GPS antenna.
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NOTESince it may not be possible to accurately display the 
vehicle position if the electromagnetic waves from 
the GPS satellite are blocked, be sure to obey the 
following:
carbon to the window glass.
 antenna.
 GPS antenna.
Situations where accurate measurement is not 
possible
In situations such as the following, accurate 
measurement may not be possible.
The US Tracking and Control Center controls the 
satellites. Sometimes the electromagnetic waves are 
stopped during upgrades or repairs to the system.
NOTEsatellites by placing objects on or around the GPS 
antenna.
 of the GPS antenna, as it could prevent accurate 
measurement.
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