Understanding What GPS Is 

Whether it was in reference to a handheld unit used by hikers or the on-board navigation system in a car, you've probably heard of GPS. But what exactly GPS and what does it do?

GPS stands for 'Global Positioning System', a worldwide navigation system that works through the use of 24 satellites orbiting nearly 11,000 nautical miles above Earth and their ground stations located from Hawaii to Colorado Springs to Diego Garcia, an atoll in the Indian Ocean. This network of satellites allows remarkably accurate mapping and point location, to within only a few meters. And if that wasn't good enough, advanced forms of GPS such as Augmented GPS, Differential GPS and Carrier-Phase GPS, can pinpoint a location to within centimeters. That kind of accuracy is truly amazing.

Advances in GPS, like other kinds of technology, are increasing in speed. If you blink your eyes, there's some new advancement in the field. Like most consumer technologies, the units started out large and each generation gets progressively smaller and more affordable for the average consumer.

A few years ago, GPS was a new term to many. Now, you'll find GPS systems in cars, boats, airplanes, farm machinery and even the laptop computer on which you may be reading this article. Handheld units prove helpful in tracking and in backcountry hiking. We're increasingly living in a world where you can't get lost. You can pinpoint just where in the Shoshone National Forest or Big Bend National Park you're standing. GPS units are like snazzier, modern-day compasses.

In a few more years, experts in the field believe that personal GPS units will be as common as cell phones. And they may not be stretching it because if you think back a decade, cell phones weren't all that common. Now, everyone from eight-year-olds to grandmas have cute, tiny cell phones so they can stay in touch with friends and family, not to mention snap and e-mail pictures.

All this mapping information from GPS is great, but "how do they do that?" It's a method called trilateration in which GPS receivers measure distance based on how long it takes to receive a radio signal. Lots of factors like where the satellites are located in space, correcting for any delays and taking signal interference into account are important when doing the necessary geometry. The good thing is you, as a personal GPS unit owner, don't have to do that geometry. Someone else does it for you. Whew!

How did the current GPS system come about? Thank the United States Department of Defense. When your job is troop movement and those movements often mean the difference between life and death, you want to be as precise as possible. The creation of the GPS system actually was a result of the arms race and needing to know exactly where the nuclear missile silos of enemies like Russia were located.

Now, the system helps on the battlefield in places like Iraq and Afghanistan. You've likely seen news video of GPS-guided missiles taking out enemy targets so that the threat to the lives of troops was lessened. Whether it's on the battlefield or the backcountry trail, GPS is changing the way we live and locate.

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