Global positioning system Introduction: For countries, people have navigated by observing the celestial bodies (i.e. stars in the sky) have located the position (in terms of latitude and longitude) of objects on the earth’s surface and have determined the exact time of observation. However, as clouds, rain, mint, fog, etc. Obscure the sky, the astronomical approach sometimes fails. The most significant development in this field that overcome these difficulties in GLOBLE POSITIONING SYSTEM (G.P.S.). The G.P.S. is a satellite based navigation and surveying system developed and adopted by the UNITED STATES DEPARTMENT OF DEFENCE (DOD) that determines with precision the three dimensional (3D) position (i.e. latitude, longitude and altitude i.e. height above mean sea level) and time of observation, 24 hours a day, in all weathers, anywhere in the whole world. GLOBAL POSITIONING SYSTEM (G.P.S.) The G.P.S. is a novel ground-to-space measurement system, (as against the conventional ground to ground i.e. terrestrial measurement system) that overcome the limitation of terrestrial system e.g. interviibillity of main stations, dependability on favourable weather conditions, difficulty in identifying a star during night observations, etc. The G.P.S. primarily designed and developed by U.S. DEPARTMENT OF DEFENCE (DOD) for military purposes, provides a global all weather instantaneous positioning system for all military people, their vehicles and missiles, etc.Presently, it also covers civilian sector such as determination of co-ordinates of objects required in Geographical Introduction System (G.I.S.) for establishment of control network, crystal deformation studies of the surface of earth, safe navigation of ship and air craft, for practise surveying and geological studies and for determination of precise Universal Standard Time (U.T.C.) DESCRIPTION OF G.P.S. The G.P.S. essentially consists of three segments i.e. (1) space segment (2) control segment. Space segment : The space segment consists of 24 satellites that circle the earth at every hour at an altitude of 20,000km (above the earth). There are 4 satellite in six circular orbits inclined at an angle of 55 degree to earth’s equator plane. The satellite are so spaced in orbit that a minimum of four will be visible to the users anywhere at any time in the world. Each satellite continuously transmits pseudo random codes at dual Frequencies and cover half the earth. They continuously broadcast 3-dimensional position and time data to its users. The Control Segment: The control segment consists of master control station (MOS) placed in the Colorado Springs, (USA), Few Monitor Station (M.S.) and ground antennas places throughout the world. This monitor station tracks all satellite in view and acquires ranging data from satellite signals. This information (from monitor stations) is further transmitted to the control station, for computing precise satellite position, velocity and time. The updated information is then further passed to each satellite through ground antennas.
Posted on: Thu, 13 Jun 2013 15:08:02 +0000
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