Long ago without GPS we walked and drove the streets the best way we knew how. Getting lost, taking wrong turns, hours of driving without knowing where we are. But GPS is a useful invention that guides us around the world. Do you know how GPS systems work? GPS stands for Global Positioning System. It was the first system available since the 1980s. The system was invented by the US Department of Defense. It was intended exclusively for military use. http://www.pcmag.com The military added interference to the signals to ensure their version was the only one with persistence. Even after 2000 it would take some time for them to arrive in cars and cellular devices. The Army, Navy and Air Force contributed plans and ideas. After being approved by the American government it became NAVSTAR. NAVSTAR was the first GPS launched in the 1970s. The GPS system was later proposed to civilians by President Reagan. He proposed this so that civilians would not get lost. http://www.tomtom.com GPS gets signals from at least three satellites to get an accurate reading of your location. The equation for measuring distance to a satellite is “distance=speed of light (186,000 miles/sec) time.” They can establish the location within 1 centimeter and provide the precise time. There are 24 satellites surrounding the earth. They circulate in a precise orbit and send signals to the earth. GPS systems work in all weather conditions. The time difference tells the receiver how far away the satellite is. Once your location is found, GPS can calculate other information, such as speed, bearing, track, distance traveled, and distance to destination. They are powered by solar energy. They also have backup batteries for when there's... half the paper... Works Cited Works Cited "Global Positioning System". www.nps.gov. NP Network. May 8, 2014. "How does GPS work?" TomTom.com. NP Network. May 8, 2014. .Aber, Jeremy, Jerry Harvey, and John Inmon. "A Brief History of GPS." academic.emporia.edu. Np, 10 December 2003. Web. 8 May 2014. .Lendino, Jamie. “The History of Car GPS Navigation.” www.pcmag.com. Np, April 16, 2012. Web. May 8, 2014. "GPS." education.natinalgeographic.com. NP Network. May 8, 2014. “GPS Accuracy.” GPS.gov. NP Network. May 14 2014. .