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Popular Mechanics ranked the handheld GPS at #17 in its list of 101 Gadgets That Changed The World, ahead of the laptop computer, digital camera, MP3 player, and the microwave oven.  It is an essential part of modern navigation systems found on airplanes, ships, trains, and automobiles.  Today, nearly everyone has access to this technology through their cars, smartphones, or dedicated GPS device and equipment.

What is GPS?  It stands for Global Positioning System, and it is a space-based satellite navigation system that provides location and time information anywhere on the Earth when there is an unobstructed line of sight to four or more GPS satellites.  Initiated in 1973, GPS as we know it today was created and developed by the U.S. Department of Defense, becoming fully operational in 1995.  Although it was originally a military project, GPS has grown to have significant civilian applications and has been widely deployed for commercial and scientific uses.  It is maintained by the U.S. Government and is freely accessible to anyone with a GPS receiver.

ConstellationGPSToday, there are up to 31 operational GPS satellites that are being maintained by the U.S. Air Force.  The United States is committed to maintaining the availability of at least 24 operational GPS satellites for 95% of the time so that users can always view at least four satellites from virtually any point on the Earth.  In fact, about nine satellites are visible from any point on the ground at any one time.  In the 24-satellite animation on the right, the number of viewable satellites from a given point on the Earth’s surface is shown — notice that the number of visible satellites changes with time.

So how does a handheld GPS use the satellites?  A simple video we found gives a very straightforward explanation about that.  Click here to see the GPS video.  All GPS devices operate essentially the same way. When you match a map to GPS coordinates, you get the familiar map-based GPS devices found on the market.

There are dozens of commercial GPS manufacturers in the market today — Garmin, Magellan, Tom Tom, Lowrance, Navigon (just to name a few).  There are different types of devices too, such as handheld or automotive units.  How do you choose one? Click here for an article to help you select the right GPS.

Of course, we’re partial to the HomeStar Pocket™ GPS.  To find out more about this small and simple device, all the information you need is on this website.