Global Positioning System

You are lost...really lost, and jokes about the male gender refusing to ask for directions aside, there is no one around to point you in the right direction.

If this scenario causes you to break out in a sweat, it's time to get a GPS, or Global Positioning System. The technology that aids in accurate bomb delivery can, on a more benign errand, provide accurate directions to Aunt Martha's house in Poughkeepsee.

In the 1970's the U.S. Department of Defense needed to accurately determine the location of their ballistic missile submarines before sending off the missiles. They launched 24 NAVSTAR satellites in particular orbits over 10,000 miles above the earth with five ground stations keeping track of the satellites via signals in the microwave section of the radio spectrum. The positions are determined from measuring distances known as trilateration. From this nascent technology, fast forward to today, where receivers like the handheld PDAs or in-car IVNS (in-vehicle navigation systems) are able to help you pinpoint where you are thanks to the help of the satellites.

You might have seen a GPS in a friend's car or used one in a Hertz rental. There is a color panel on the dashboard that shows you maps and allows you to enter data via onscreen buttons, for instance Aunt Martha's street and city. Once you have entered the information, audio prompts tell you when to turn left or right. There are even "geo-caching" games where handheld GPS are used to find hidden treasure.