GPS Overview Waypoint Data

     GPS or Global Positioning System is a satellite navigation system funded and controlled by the U.S. Department of Defense (DOD).  GPS uses one-way satellite communication as a means to determine user location based on a scheme using relative distances (the original intent of the system was to supplement the tracking of ballistic missiles). The GPS Operational Constellation or "NAVSTAR" consists of 24 Rockwell International Block II satellites: 21 navigational satellites and 3 active spares. Future plans include 21 Martin Marietta Block IIrs satellites.