The Global
Positioning System (GPS) is a satellite-based navigation system
made up of a network of 24 satellites placed into orbit by the
U.S. Department of Defense. GPS was originally intended for
military applications, but in the 1980s, the government made
the system available for civilian use. GPS works in any weather
conditions, anywhere in the world, 24 hours a day. There are
no subscription fees or set-up charges to use GPS. (From the
Garmin GPS Web site, www.garmin.com)
GPS is funded
by and controlled by the U.S. Department of Defense. It provides
satellite signals that can be processed in a GPS receiver, enabling
the receiver to compute position, velocity and time. Four GPS
satellite signals are used to compute positions in three dimensions
and the time offset in the receiver clock.
