HI!!
another week just passed by. Its time for another geekmail.
This week i am going to write about GPS.
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What is GPS??
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GPS stands for Global Positioning System.
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How does it work
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It works on the basis of Trilateration.
The reciever calculates its coordinates by making use of the
27 Earth-orbiting dedicated satellites (24 in operation and three extras in case one fails) .
The U.S. military developed and implemented this satellite network as a
military navigation system, but soon opened it up to everybody else.
Each of these 3,000- to 4,000-pound solar-powered satellites circles
the globe at about 12,000 miles (19,300 km), making two complete rotations every day.
The orbits are arranged so that at any time, anywhere on Earth, there are at least four
satellites "visible" in the sky.
The GPS reciever locates atleast 4 satellites at any given time ,
calculate their distances an then find its own location based on the calculated data.
It is based on the mathematical operation called trilateration.
Trilateration in 3D id a lil' difficult to understand so lets begin with 2D
Consider you r in a place 180 kms away from Bangalore.
You could be anywhere on a circle of radius 180 kms with bangalore.
Now if I say u r 20 kms away from hassan, u r on a circle of 20 km radius
with hassan as centre. But from the above data. there can be only 2 points where the
circles can intersect, narrowing down your location to two points. now if i
say u r 100 kms away from mysore then there can b only one point where the
three circles intersect. so you get your precise location.
Trilateration in 3D is similar but there instead of circles spheres are
used to find the altitude.
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What r satellites for
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In order to make this simple calculation, then, the GPS receiver has to know two things:
*The location of at least three satellites above you
*The distance between you and each of those satellites
The GPS receiver figures both of these things out by analyzing high-frequency,
low-power radio signals from the GPS satellites. Better units have multiple
receivers, so they can pick up signals from several satellites simultaneously.
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What is its use??
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It is used to find the precise location (absolute) of a GPS transmitter.
It may be embedded in a watch or it may be a separate unit.
This is extremely helpful for navigation. You can develop maps,
set your course of travel and see in real time your path.
this is used in automatic vehicle navigation where u set a course and move along it.
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How is it going to affect me?
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Well for the time being it is not. But sooner or later it is going to be important.
These days you can find GPS enabled Wrist watches.
Who knows on day this may be the conversation
Dude1: Hey!! how r u?? where do u stay these days?
Dude 2 : I am fine. These days i put up at 79*E,90*N
Hope u gained something....
Vaishak Suresh
vaishaksuresh@yahoo.com
http://www.geocities.com/vaishaksuresh
(
geocities.com/vaishaksuresh)