ConnDOT: GPS 101

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GPS 101
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The term GPS means “Global Positioning System.” This is a system of 28 Earth-orbiting satellites established by the United States Department of Defense.  The satellites in the GPS network are arranged in such a way that you can see at least 4 of them at a time from any given point on Earth. Actually, you can’t really “see” them; it is your GPS device that is doing the seeing.  A GPS device can lock onto 4 or more available satellites in the GPS satellite network quickly and thus provide a point of reference.

Since its development by the Department of Defense in the 1970s, the GPS has adapted to a number of civilian and commercial uses. GPS was originally created to allow military ships, aircraft, and ground vehicles to determine their exact location anywhere in the world, in any weather.  Today, GPS is being incorporated into the on-board computers of new cars and such diverse uses as grade leveling at new construction sites.

At the Connecticut Department of Transportation, GPS is used to record the location of water and storm lines, utilities, roads, sidewalks and is an important tool for highway maintenance crews, commercial vehicle operators, transit providers and emergency responders.  GPS also helps make records and mapping more accurate - thus saving time and money during construction  

GPS utilizes satellites to pinpoint the exact location and movement of vehicles.  Each satellite transmits a lowpower, continuous signal that can be detected and decoded by a GPS receiver.  Information contained on the satellite signal enables the receiver to compute satellite coordinates and make range measurements to all satellites in view.  Measurements from four or more satellites are then used to derive the receiver's position (latitude, longitude, and height) and time.

Originally, the Department of Defense designed this system with a strategic military application in mind. However, the widespread usefulness of the GPS network was quickly recognized and it was made available for civilian use during the 1980’s.

Today, many personal vehicles are equipped with GPS that can provide directions to the motorists, or transmit location information to emergency personnel in the