GPS

GPS

The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations. GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimetre! In a sense it's like giving every square meter on the planet a unique address. GPS receivers have been miniaturized to just a few integrated circuits and so are becoming very economical. And that makes the technology accessible to virtually everyone.

How Does GPS Work?

[1] The basis of GPS is "triangulation" from satellites.
[2] To "triangulate," a GPS receiver measures distance using the travel time of radio signals.
[3] To measure travel time, GPS needs very accurate timing which it achieves with some tricks.
[4] Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.
[5] Finally you must correct for any delays the signal experiences as it travels through the atmosphere.