GLOBAL POSITIONING SYSTEM (GPS).

What is GPS?

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 setup
charges to use GPS.

How it works

GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information
to earth. GPS receivers take this information and use trilateration to calculate the user's exact
location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite
with the time it was received. The time difference tells the GPS receiver how far away the satellite
is. Now, with distance measurements from a few
more satellites, the receiver can determine the user's position and display it on the unit's
electronic map.