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What to Do When...
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Accuracy and Error
GPS satellites are managed by the US Department of Defense and have a very high accuracy.
However, when multipath effects are caused by reflections from buildings and the like, errors
may occur.
When there is obstruction between the GPS antenna and the GPS satellites, signals cannot be
received. Since at least three signals must be simultaneously received to establish your
position, Navigation cannot establish your position by GPS in the following locations.
When an obstruction (a load or the like) exists on or in the vicinity of the GPS antenna, it may
not be possible to receive signals from the satellites.
CHECK
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Since the GPS satellites orbit the earth, the reception of signals at a given position varies with
time. Note also that signals from satellites close to the horizon are susceptible to the effects of
obstructions.
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GPS satellites are managed by the US Department of Defense and their accuracy is sometimes
reduced deliberately.
About measurement accuracy
About GPS Satellite Quality and Status
Underground, in a tunnel or
in an indoor parking structure
Surrounded by obstructions
such as tall buildings
In a building
Densely wooded areas
Under an elevated road
On a cliff side road or at a
cavern opening
