The Global Positioning System (GPS) uses a network of 24 satellites sending out signals to accurately locate you anywhere on the Earth's surface. Mobile GPS units are available for use in cars or on boats. There are even portable units for mountaineers.

GPS navigation forms the basis of new automatic vehicle locator systems (AVLS) for buses. These could make bus travel much simpler.

The GPS network - 24 satellites in 3 orbits of 8

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