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Helpful tips
4. Accuracy and errors
Positioning accuracy
The GPS is a very accurate satellite system controlled by the U.S. Department of Defense.
Errors may result due to the occurrence of a multipath caused by reflections off of buildings or
other structures.
GPS signal quality and reception conditions
Any obstruction coming between the satellite and the GPS antenna will disrupt signal
reception from the satellite.
Also, 3 or more signals must be received simultaneously to enable positioning. When driving
along locations such as those shown below, GPS positioning is not possible.
In addition, obstructions placed on or near the GPS antenna (such as cargo) will disrupt
signals from the satellite.
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 cliffside road or at a
cavern opening
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Because the GPS satellite orbits the earth, signal reception conditions may vary depending
on the position of the satellite even if driving in the same area. Signals from a satellite orbiting
near the horizon are more likely to be obstructed.
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The GPS satellite is controlled by the U.S. Department of Defense and can be deliberately
made to lose positioning accuracy.
