Mitsubishi NR-261 Manual page 9

Between closely-spaced trees
The US Tracking and Control Centre controls the satellites.
Sometimes the electromagnetic waves are stopped during
upgrades or repairs to the system.
NOTE
Do not block the electromagnetic waves, from GPS satel-
lites by placing objects on or around the GPS antenna.
Avoid using 1.5 G digital communication equipment close
to the GPS antenna. Doing so may make it impossible to
accurately measure position.
Mitsubishi Multi Communication System
Situations where errors occur in the current location
and direction
Errors sometimes occur when the accuracy of the GPS
satellite unit is poor.
The GPS satellites are controlled by the United States
Department of Defense, so sometimes the satellite itself
intentionally sends incorrect position data. The measure-
ment error will increase in this kind of situation.
Sometimes sufficient accuracy is not possible because the
distribution of the GPS satellites is poor (when the satel-
lites are aligned in approximately the same direction or
height). (The best accuracy for GPS measurement is when
signals are received from multiple satellites; a satellite
directly over the vehicle and others just over the horizon
to the north, south, east and west.)
Regarding the height and directional accuracy of GPS
measurement, errors are slightly more likely in the hori-
zontal direction.
Electromagnetic waves from satellites higher than the
vehicle height can be received, but electromagnetic waves
cannot physically be received from satellites positioned
lower than the vehicle height (on the far side of the Earth).
This means that an adequate height comparison is not pos-
sible.
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