Drawn from the radio systems developed for World War II, the Global Positioning Systems (GSP) so familiar to us today came directly from military applications. During the Cold War it became apparent that the military needed a better ability to locate positions of both enemy and military missiles and air planes. When Russia launched the first satellite into space, two scientists at the Applied Physics Laboratory began monitoring radio transmissions from the satellite. By observing the Doppler shift of the radio frequency during transmission to earth, they were able to calculate the actual position of the satellite when the transmission was made. Much to the surprise of Russia, a complete description of the orbits of the satellite was released by the United States. Russia was not able to calculate the orbit of its own spacecraft.
Carrying the idea further along, it was clear that monitoring positions in space or on earth was possible using satellites. The issue was the extensive cost to set up this technology. It was extensive enough that a private company could not bear such a cost. In stepped issues of the Cold War. The military had three issues and a GPS system would solve most of those issues. There was a need to know exactly where the submarine ballistic missiles, the USAF strategic bombers and intercontinental ballistic missiles were located. The development of Russian mobile missiles pushed the envelope even more. Each military group had begun looking into the problem. Finally, in 1973 at a meeting at the Pentagon, combining forces of all the military units the Navstar-GPS System was born
The satellites sent in to orbit were not only sent up with the ability to locate distances. Also included were atomic clocks with the satellites that allowed both the position and the time of the location to be accessed. This allowed the GPS system to include timing functions in its receivers. The GPS satellite system is still controlled and operated by the US military.
In 1983 after a Korean civilian plane was shot down by Russia after it strayed unknowingly into Russian air space, President Reagan authorized the GPS systems to be made available world wide to prevent similar reoccurances. The GPS system had signals sent on two different frequencies and controlled the frequencies sent out for civilian use. The accuracy of the military system was within 65 feet anywhere on the planet; the accuracy of the civilian uses was accurate to 300 feet. In 1996, President Clinton issues a directive that ordered the Pentagon to cease controlling the civilian frequencies. This was stopped in the year 2000, leading to the GPS devices we have today.
Civilian uses of the GPS include clock synchronization, celluar telephony, vehicle tracking, person or animal tracking, fleet tracking, GPS tours, map making, navigation, aircraft tracking and pedometers.
A new use of the GPS systems includes wireless broadband systems for communication. These wireless systems will possibly replace landlines in the future, seeing the end of cable and telephone poles.