The Global Positioning System (GPS) is a global navigation satellite-based navigation system designed by the US department of defense and managed by the US Air Force 50th Space Wing. GPS was originally developed to be used for military purposes, however, in the 1980s, the US government made the use of the system to be free for everyone, anywhere for navigation purposes. Its official name is NAVSTAR GPS. It uses a constellation of between 24 and 32 medium Earth orbit satellite that transmits precise radio wave signals, which allow GPS receivers to determine their current location, time and their velocity in any kind of weather.  Read more...