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Originally designed for military and intelligence applications at the height of the Cold War in the 1960s, with inspiration coming from the launch of the Soviet spacecraft Sputnik in 1957, the global positioning system (GPS) – is a network of satellites that orbit the earth at fixed points above the planet and beam down signals to anyone on earth with a GPS receiver. These signals carry a time code and geographical data point that allows the user to pinpoint their exact position, speed and time anywhere on the planet.

Transit was the first satellite system launched by the USA and tested by the US Navy in 1960. Just five satellites orbiting the earth allowed ships to fix their position on the seas once every hour. In 1967 Transit was succeeded by the Timation satellite, which demonstrated that highly accurate atomic clocks could be operated in space. GPS developed quickly for military purposes thereafter with a total of 11 “Block” satellites being launched between 1978 and 1985.

However, it wasn’t until the USSR shot down a Korean passenger jet – flight 007 – in 1983 that the Reagan Administration in the US had the incentive to open up GPS for civilian applications so that aircraft, shipping, and transport the world over could fix their positions and avoid straying into restricted foreign territory.

Upgrading the GPS was delayed by NASA space shuttle SS Challenger disaster in 1986 and it was not until 1989 that the first Block II satellites were launched. By the summer of 1993, the US launched their 24th Navstar satellite into orbit, which completed the modern GPS constellation of satellites – a network of 24 – familiar now as the Global Positioning System, or GPS. 21 of the constellation of satellites were active at any one time; the other 3 satellites were spares; in 1995 it was declared fully operational. Today’s GPS network has around 30 active satellites in the GPS constellation.

Today, GPS is used for dozens of navigation applications, route finding for drivers, map-making, earthquake research, climate studies, and an outdoor treasure-hunting game known as geocaching.

Through her integration of classical ballet movements into traditional Persian dancing Farzaneh Kaboli has created a new and sophisticated form of Persian dance. Her work is a celebration of the rich tradition of folk music and dance within Iran. Some day she hopes to show her work to a wider audience.

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What is GPS?
GPS or the Global Positioning system is formed with about 24 satellites which are located in the orbit by the United States’s Department of Defense. GPS functions in any weather condition, 24 hours a day, any where in the world without subscription fee and set up charge. GPS satellites revolve around earth in a very accurate orbit two times a day, transmitting information via signals to the earth.

The way GPS works
The GPS receivers on the earth fetches the signals to triangulate user’s exact position. Basically, the GPS receiver analysis the time a signal was sent to the satellite with the time it received the signal. The difference in time indicate the distance of the satellite. The receiver along with the distance measurement from other satellites determines exactly the user’s location and displays it on the electronic map of the unit.


To track movement and calculate latitude and longitude position, ie the 2D position, the GPS receiver must lock at least three satellite signals. Similarly, to determine 3D position, ie latitude, longitude and altitude, the receiver must lock four or more than four satellite views. Once the position of the user is determined, the GPS receiver can track other information such as trip distance, speed, bearing,sunrise and sunset time, distance to destination and more.
Modern GPS receivers equipping parallel multi channel design makes it extremely accurate. As on date 12 parallel channel receivers when first tuned on lock satellites strongly even in dense or urban cities. Certain factors like atmosphere and other source can cause error, affecting accuracy of the GPS receivers. Recent GPS receivers having WAAS- Wide Area Augmentation System can improve accuracy in less than 3 meters on average.

How accurate is GPS?
Better accuracy is achieved also through Differential GPS, DGPS that can correct GPS signal in about five meters. The system of DGPS comprises network of towers receiving GPS signals and retransmit the corrected signls using Beacon transmitter. On the other side the user must also posses a Beacon receiver and antenna to their GPS for receiving the correct signal.


The GPS space segment consist of 24 satellites that are orbiting above us apart 12000 miles. The satellites travel at a speed of about 7000 miles an hour. Powered by solar energy, the GPS satellites possess on board batteries for back up to keep them running during solar eclipse.