WHAT IS GPS?

This page contains a brief description of GPS for the layperson.

GPS stands for Global Positioning System.  Originally
developed by the US Department of Defense, GPS is now
widely used by the civilian sector.  GPS relies on
24 satellites in orbit to broadcast timed signals
toward the surface of the Earth.  These signals are
picked up by users on the ground (at sea, or even in
aircraft) with GPS antennas.  Signals from multiple
satellites reaching a single antenna allow the
location of the antenna to be calculated.