The Global
Positioning System (GPS) is the only fully functional
Global Navigation Satellite System (GNSS). The GPS uses a
constellation of between 24 and 32 Medium Earth Orbit satellites
that transmit precise microwave signals, that enable GPS receivers
to determine their current location, the time, and their velocity
(including direction). GPS was developed by the United States Department
of Defense. Its official name is NAVSTAR-GPS. Although NAVSTAR-GPS
is not an acronym, a few backronyms have been created for it. The
GPS satellite constellation is managed by the United States Air
Force 50th Space Wing.
