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General description of what
GPS is and how it works.
GPS (Global Positioning System) is the only system today
able to show you your exact position on the Earth anytime,
in any weather, anywhere. GPS satellites, 24 in all, orbit at
11,000 nautical miles above the Earth. They are
continuously monitored by ground stations located
worldwide. The satellites transmit signals that can be
detected by anyone with a GPS receiver. Using the receiver,
you can determine your location with great precision.
The satellites are positioned so that we can receive signals
from six of them nearly 100 percent of the time at any point
on Earth. You need that many signals to get the best
position information. Satellites are equipped with very
precise clocks that keep accurate time to within three
nanoseconds- that's 0.000000003, or three billionths of a
second. This precision timing is important because the
receiver must determine exactly how long it take s for
signals to travel from each GPS satellite. The receiver uses
this information to calculate its position.
