![]() Transportation companies employ GPS receivers to keep track of their fleets, and police cars, fire engines, and ambulances use them to speed their response to emergencies. For example, engineers building the English Channel tunnel used GPS-provided measurements to ensure that the French and British teams digging from opposite ends would meet precisely in the middle. forces to maneuver during sandstorms and at night aircraft, ship, tanks, and individual troops made use of more than 9,000 receivers throughout the Gulf region.Įventually released for civilian use, GPS began finding an increasing number of applications in the 1990s. GPS played an important role in Operation Desert Storm, enabling U.S. Brad Parkinson, then at the Department of Defense, directed its development for its original military functions. Known officially as NAVSTAR (Navigation Satellite Timing and Ranging), GPS was envisioned as early as the 1950s by Ivan Getting, who subsequently championed its construction. The microprocessor then applies a sophisticated form of triangulation to determine its own position. Four atomic clocks on each satellite keep track of time to within 3 billionths of a second, a level of accuracy that enables a receiver’s microprocessor to precisely measure the distance to each satellite from which it receives signals. Using signals from at least four satellites, the receivers can calculate their own location-latitude, longitude, and elevation-to within 100 feet the more satellites the receiver has within its line of sight, the more precisely location can be determined, in some cases within 20 feet.Įach satellite continuously transmits three vital pieces of information an identification code, data on its own location in space, and a time signal. ![]() ![]() Circling the globe once every 12 hours at an altitude of more than 12,000 miles, the satellites maintain positions relative to one another that enable handheld or vehicle-mounted units to receive signals from as many as six of them at once, from virtually any point on the planet’s surface at any given time. Among the thousands of satellites orbiting Earth are 24 that work together as the key elements of the Global Positioning System (GPS), a navigational tool of unprecedented precision. ![]()
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