GPS relies on at least 24 satellites flying 20,000 kilometers overhead in one of six different orbital paths, tracing out what looks like a toy model of an atom. With their solar panels extended, each of these 1-ton satellites is about the same size as a giraffe. At any given moment, each satellite beams out a signal identifying itself and giving its time and location.
Your GPS-enabled phone or car captures that signal and compares the time it was received to the time it was transmitted. A quick calculation involving the speed of light allows the device to figure out the distance to that satellite. If you have your distance to two or three satellites, you can triangulate your position on the Earth.
The idea behind GPS comes from the very beginnings of the Space Race. In 1957, the Soviet’s newly launched Sputnik satellite emitted a characteristic radio beep that could be tuned in to as the object passed overhead. While the rest of the U.S. was freaking out, two scientists at the Applied Physics Laboratory realized they could use those transmissions to pinpoint where the satellite was. As Sputnik approached, its radio signals would get compressed a little, shortening their wavelength, and as it receded, the wavelengths would lengthen. This is known as the Doppler effect and can easily be heard as an ambulance speeds toward you, the pitch of its siren getting higher.
The full GPS fleet was completed in 1994 and now at least 32 satellites are in orbit to provide redundancy. During the same time, the Russians developed and launched GLONASS, which works on principles similar to GPS, and is currently the only alternative location-finding system in the world.
Your GPS-enabled phone or car captures that signal and compares the time it was received to the time it was transmitted. A quick calculation involving the speed of light allows the device to figure out the distance to that satellite. If you have your distance to two or three satellites, you can triangulate your position on the Earth.
The idea behind GPS comes from the very beginnings of the Space Race. In 1957, the Soviet’s newly launched Sputnik satellite emitted a characteristic radio beep that could be tuned in to as the object passed overhead. While the rest of the U.S. was freaking out, two scientists at the Applied Physics Laboratory realized they could use those transmissions to pinpoint where the satellite was. As Sputnik approached, its radio signals would get compressed a little, shortening their wavelength, and as it receded, the wavelengths would lengthen. This is known as the Doppler effect and can easily be heard as an ambulance speeds toward you, the pitch of its siren getting higher.
The full GPS fleet was completed in 1994 and now at least 32 satellites are in orbit to provide redundancy. During the same time, the Russians developed and launched GLONASS, which works on principles similar to GPS, and is currently the only alternative location-finding system in the world.
