Q: What can people do with a GPS?
A: Probably the most important thing you can do is to find your way around in an unfamiliar place. A GPS really produces just a stream of numbers (latitude and longitude) which most people would find meaningless. But when the GPS is linked with a digital map and navigation system, it can tell you where you are; the nav system can find a place, and tell you how to go there from where you are. If you take the wrong turn and get lost, the GPS can figure that out by comparing your path with the route you were supposed to have taken, and it notifies the nav system, which re-routes you.
If you're lost on a hike, or in a boat stranded in the ocean, a nav system is no use, but you could radio a rescue team and give them your latitude and longitude.
Once, on a visit to Washington DC, I'd parked my car outside a train station, in a very large parking lot. When I got back at night, I'd forgotten where I'd parked, and the button on the key fob was too far from the car to honk the horn. Fortunately I'd recorded my driving path from a GPS, that was in my pocket. I walked to the last spot on the track, tried the key fob button again, and it located the car, which was just a little distance away.
GPS reports speed and time as well as location. You could use it to correct your watch.
GPS tracks police cars, taxis, trucks and other fleet vehicles, and reports their location to control centers. At Digital Geographic, we study GPS data to figure out where vehicles get held up, and work out ways to move them through more quickly.
My friend Donald Cooke has written a fascinating book, Fun with GPS. He describes experiments such as putting GPS on skiers. In fact you could put GPS on anything that moves. Or on things that don't seem to move—scientists use very accurate GPS devices to study how land moves during earthquakes.
When GPS was first introduced many years ago, a receiver was so big that it needed to be carried around in a small truck. By the year 2000, devices were as small as a pack of cards. Now a GPS chip is the size of a fingernail, and it can be slipped into a cell phone. As we figure out how to make these things smaller and more accurate, we can track more things: kites, soccer balls. What do you think you'd like to track when you grow up?