global positioning system

A system of satellites and mobile receivers that makes it possible to determine each receiver’s position with high accuracy. Used by pilots, truckers, car drivers and by many smartphone users world-wide, it is an industrial application of Einstein’s theories of special and general relativity: Without taking into account the effects predicted by these theories for moving clocks in a gravitational field, there would be errors of roughly 10 kilometres per day of operation in the determination of positions on earth.