HOW GPS WORKS

Brief history

1960: The first ever navigational system – Transit – is launched by the US Navy, and used to accurately locate ballistic missile submarines and ships.

1967: The US Air Force develops the Timation satellite which proved the ability to place accurate clocks in space, a technology that GPS relies upon intensively.

1973: US Navy and Air Force combine their respective navigation systems in an effort to develop a Defence Navigation Satellite System which would later become NAVSTAR GPS.

1978: The first of the experimental GPS Block I satellites is launched (which comprised 10 satellites, the last of which was launched in 1985).

1983: A Korean civilian airliner is shot down by Russian fighters after accidentally intruding into Soviet air space. US president Ronald Reagan subsequently declassified the NAVSTAR GPS system to prevent any such tragedy from happening again, thereby making GPS available to civilians.

1989: The first of the GPS Block II modern satellites is launched.

1990: NAVSTAR GPS becomes operational.

1991: The first Gulf War begins. Although not fully operational at the time, GPS allows the American military to prove the usefulness of the system by obtaining accurate coordinates in the featureless Iraqi desert.

1994: The last of the Block IIA satellites is launched, completing the constellation of 24 GPS satellites.

1995: The Block II NAVSTAR GPS constellation is declared to be fully operational.

2005: The first modernised GPS satellite is launched and begins transmitting a second civilian signal for enhanced user performance. Six more of these are launched between 2005 and 2008, bringing the total number of GPS satellites in orbit to 31.Brief history

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