GPS (Global Positioning System)

By Susie Howdeshell

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 centimeter! 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. These days GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers.

From http://www.trimble.com/gps/what.html

Disappearing Lake Chad

These satellite images clearly show the shrinking of Lake Chad.

Do you recognize this?