GLOBAL POSITIONING SYSTEM |
GPS (Global Positioning System) is the only system today able to show you where your exactly position on the earth at anytime and any weather condition. 24 satellites are all orbit around the earth at 11,000 nautical miles or approximately 20,200 kms. above the earth. The satellites are placed into six different orbital planes and 55 degree inclination. They are continuously monitored by ground stations located worldwide. |
GPS ELEMENTS We can divide GPS system into three segments.
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SPACE SEGMENT The space segment comprises a network of satellites . The complete GPS space system includes 24 satellites, 11,000 nautical miles above the earth, take 12 hours each to go around the earth once or one orbit. They are orbit in six different planes and 55 degrees inclination. These positions of satellites, we can receive signals from six of them nearly of the time at any point on earth. Satellites are equipped with very precise clocks that keep accurate time to within three nanoseconds ( 0.000000003 of a second or 3e-9)
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USER SEGMENT As the pilot fly , the GPS receiver continuously caculates the current position and display the correct position / heading.The GPS unit listen to the satellite’s signal and measure the time between the satellites transmission and receipt of the signal. By the process of triangulation among the several satellites being received, the unit computes the location of the GPS receiver. GPS receiver has to see at least four satellites to compute a three dimensional position (it can compute position with only three satellites if know altitude). Not only latitude and Longitude , but altitude as well. There are numerous forms of display among the various manufacturer. No frequency tuning is required , as the frequency of the satellite transmissions are already known by the receiver. |
CONTROL SEGMENT The control Segment of GPS consist of:
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OPERATION The principle of GPS is the measurement of distance between the receiver and the satellites. The satellites also tell us exactly where they are in their orbit above the earth . The receiver knows our exact distance from satellite , knows the distance between satellites. GPS receivers have mathematical method by computer to compute exactly where the GPS receiver could be located. |
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Wednesday, 26 October 2011
GLOBAL POSITIONING SYSTEM
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