GPS device, how a global navigation clock can tell where you are

A GPS device is one of the most amazing pieces of technology ever invented by the human race. Considering you can pick one in any store around the corner, for under $100, just serves to make it seem even more unbelievable. Do you know what is involved in order for a GPS device to tell you exactly where you stand anywhere on this planet? Oh boy, you’re in for a big surprise….

Contrary to popular belief, a GPS device doesn’t “communicate” with satellites. In fact, it’s just a careful listener. Indeed, there is a constellation of GPS satellites orbiting around Earth; and at any moment, in any place you might be, there will always be some of them that will be “visible” in the sky (except if you’re in a deep valley, canyon, or surrounded by sky scrappers). On board the GPS satellites, an atomic clock is responsible to keep the time with the highest degree of accuracy possible – that’s the secret that makes it all possible. With that in mind, the GPS device receivers tracks down tiny variations in the time the data stream from the several satellites takes to reach it, and uses that data to pinpoint your exact location.

Although it sounds like science fiction, this is one example of how “theoretical science” can indeed have practical applications. Just imagine how the world would be without "GPS devices". Planes and ships all around the world would be “blind”, using century old navigation techniques that can be put off by simple events like fog or a faulty chronometer. The GPS device is one of the devices responsible for us to have the “modern” in the “modern world”.