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Navigation Systems

The Global Positioning System (GPS) is a navigational system comprised of 24 satellites orbiting the earth at about 7,000 miles per hour. The satellites continuously transmit radio signals that GPS receivers use to calculate a user’s location. Three satellites are required to obtain latitude and longitude on the earth, while four satellites are required to obtain latitude, longitude, and precise altitude. This process is called trilateration. Standard GPS systems are accurate within 50 feet (about 15 meters). Advanced GPS systems that also use ground relay stations can improve accuracy by pinpointing the location within 3 to 10 feet (about 1 to 3 meters). Used with electronic maps, the receiver constantly sends signals to update a display with upcoming roads, intersections, landmarks, airports, hospitals, and businesses.