Global Positioning System (GPS)

Global Positioning System(GPS) 

The Global Positioning System(GPS)  is a satellite based navigation system  which made up of a network  of satellites placed into orbit by the US department of defense. It was originally intended for military application in 1980s the government made the system available for civilians use. GPS works 24 hour  a day ,in any weather condition anywhere  in the world . There are no subscription or setup charges to use GPs.

GPS satellite system comprises 27 satellite that make up the GPS space segment orbiting about 12000 miles above the earth surface. GPS satellites circle the earth twice a day in a precise orbit and transmit signal information to earth.GPS receivers take this information and use the triangulation technique to calculate the user exact location. Essentially GPS receiver compare the time a signal is transmitted by a satellite with the time it is received.

The time difference tells the GPS receiver how far is the satellite. Now, with distance measurements from a few more satellites, the receiver can determine the users position and display it on the units electronic map. A GPS receiver must be locked onto the signal of at least three satellite to calculate a 2D position and track movement with 4 or more satellite in view, the receiver can determine the user’s  3D position .One’s the position has been determined, the GPS unit can calculate other information  such as speed,  bearing, track,  trip distance , distance to destination , sunrise and sunset time  and so on.

Now GPS satellites are powered by solar energy with a backup batteries on board to keep the running in the event of a solar eclipse and the other  emergencies. Small rocket boosters make them fly in the correct orbital path.GPS satellite transmit two low power  radio signal designated  as L1 and L2, the civilian version of GPS uses the L1 frequency of 1575.42 MHZ in UHF band.

GPS signal  contains a three different bits of information, pseudorandom code, ephemeris code,   almanac  data.  The  pseudorandom code is an ID code that  identifies the satellite which is transmitting data.  Ephemeris  data contains important information about the status of satellite the ,current date and time. Almanac  data tells the GPS part of the signal is essential for  determining the position of an object.

GPS Application

GPs has  the variety of application on land ,at the sea  and in the air. GPS  can be used anywhere except in the place where it is impossible to receive the signal such as  inside most building in the cave and subterrarian  and underwaters.

1.Application of GPS in navigation of general aviaton and commercial aircrafts.

2.Surveyors use of GPS for an increasing portion of their work. IT is also time saving method by reducing the setup time survey site and provide accuracy.

3.GPS is also used in recreational activities. IT is popular amoung hikers, hunters, snowmobiles, mountain bikers.

4.GPS is commonly used in automated in automobiles. More sophisticated system that show position on street map is also available. These system allow a driver the to keep track of position and suggest the best route to follow to reach a designated location.

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