The Global Positioning System is a constellation of satellites built by the US Department of Defense; the first Navstar GPS satellite was launched in 1978, and the system reached full operational capability in 1995 with a complete constellation of 24 satellites. Receivers fix their position by measuring signal travel time from several satellites at once, giving location and time to within metres. Initially a military system, civilian access was opened progressively, and the deliberate accuracy-degrading 'Selective Availability' was switched off in 2000, sharply improving public precision. It is now embedded in phones, vehicles and survey equipment worldwide.
It underpins modern surveying, logistics and navigation, and the continuous stream of location data it enables now structures how cities are mapped, analysed and managed in real time.
See it on the timeline →