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Appendices
GPS - the Global Positioning System - is a
navigation revolution. It’s a technology that pinpoints a
user’s location anywhere in the world, 24 hours a day,
regardless of the weather.
Designed by the United States’ Department of
Defense for use by the military, the GPS System was
made available to civilians for use in aviation, marine
surveying and general outdoor/ recreation markets.
Today, millions of people utilize the accuracy and
convenience of this amazing technology to hunt, fish,
hike, fly, cruise and sail. GPS consists of a constellation
of 24 satellites orbiting some 12,000 miles above the
earth.
These satellites transmit signals containing time and
orbital data to calculate satellite position and almanac
data. Meanwhile, receivers used on the ground, sea and
air search the sky for the satellites. The GPS unit needs
to acquire good signals from at least three satellites to
determine a position on the surface of the earth. A
fourth signal is required to get three-dimensional
positioning which determines elevation or altitude.
Appendix B
What is GPS?