Garmin APOLLO GX65 - Manual (Page 313)

GPS Navigation
GPS
Overview
The Global Positioning System (GPS) is a constellation
of 24, or more, satellites in six orbit lanes 10,898 nautical
miles above the earth at an inclination angle of about 55
degrees from the equator. Each satellite orbits the earth
twice in 24 hours.
The GPS was developed and the satellites launched
by the U.S. Department of Defense with the original
intent of supplying highly accurate position fix
information for military applications. In recent years,
commercial applications for the information provided
by this system have steadily increased in the civilian
sector. Some of the more popular civilian uses of the
system include surveying and position fix data
recording for civil engineering applications, and a
broad range of marine, aviation, and terrestrial
navigation applications.
While orbiting the earth, each GPS satellite transmits
complex streams of data containing the operational
status and orbital location of all the satellites in the
system. The Apollo GX receives this data stream and
GPS Navigation
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