At its simplest, the Global Positioning System—GPS—is no harder to understand that those junior high math problems that began, "If Train A leaves Chicago traveling at 85 miles an hour…" GPS is no more than measuring time and distance to determine where you are. But when it comes to the nitty-gritty—the actual measuring—there are so many measurements to be made over such vast distances and so many gotchas lurking in those measurements that without the benefit of high tech you could easily be thrown off by half a continent.

The simple explanation behind GPS is this: If you know how far away you are from three known points, you can use high school math to determine exactly where you are. Here's how it works when those known points and those measurements come from outer space.

The Satellite System

Hari Maurya wrote thts awesome article thnx rahul for suggested me a topic for my coming college presentations

It's totally my pleasure Hari.

ye toh mera topic tha....where is ur pleasure rahul