Knowing something about GPS

Know something about GPS
What is GPS?
It's a device used widely in cars, on smartphones and in fitness devices. But what exactly is GPS, and how is it able to pinpoint our exact location anywhere on Earth? How does it work? The Global Positioning System (GPS) is a constellation of up to32 satellites that orbit at a height of 26,600km above Earth. The satellites are owned by the US Department of Defense, but anyone can use the signals from those satellites, provided they have a receiver. For the receiver to work, it needs to be able to "see" four of the satellites. When you turn on your receiver, it may take a minute or so to locate these satellite signals, then to download data from the satellite before positioning can commence. Fundamentally, two things need to happen for this to work effectively: 1) The GPS receiver measures the distance from itself to a satellite by measuring the time a signal takes to travel that distance at the speed of light. 2) When the satellite's position is known, the GPS receiver knows it must lie on a sphere that has the radius of this measured distance with the satellite at its centre. The receiver need only intersect three such spheres, as seen in the image below. This process, known as trilateration, is an effective means of determining absolute or relative locations. But there's a problem. Although the GPS satellites have veryexpensive atomic clocks on board – and therefore know what time their signals are transmitted – the GPS receiver has a very cheap clock. That means there is uncertainty about the "receive" time. So, instead of three satellites, the GPS receiver must receive four, so it can account for what's known as the receiver clock drift. Courtesy:Indian Technocracy

2 comments :

Anonymous said...

Gps invented in india...????

Anonymous said...

Gps invented in india...????

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