The GPS instruments takes the help of dedicated satellites for this purpose. But what is the technology behind it? Please explain.
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It is a radio wave signal that goes back and forth.
It uses satellite signals in relation to your position on the earth and then uses this information along with local map information to give you the display.
Basically there are three satellites dedicated to GPS. GPS device has to align with all satellites to locate. Consider it like an upside down triangular pyramid. so consider yourself with GPS at the tip of it.
Your GPS unit triangulates it's position with at least 3 satellites in space. Based upon distances from each satellite, your position can be determined.
Through simple triangulation of satellites... The GPS receiver receives a signal from multiple satellites and where the signals meet is where you are. The location on the GPS unit is matched to a GIS coordinate system. Such as UTM coordinate system.
Here is all About GPS http://en.wikipedia.org/wiki/GPS
GPS satellites will broadcast the time of the day and its position, and when they do they do it at exactly the same time. Although these signals travel at the speed of light, they still take a finite amount of time to reach you. A signal will take longer coming from a satellite that is far away than from a satellite that is closer to you. Since each broadcast is sent by all the satellites at the exact same time, you can determine your position by looking at the time delay between when your GPS receiver gets the message from each satellite.
Each GPS satellite broadcasts the time given by its internal clock, and also information on its current position. Because the speed of light is finite, your receiver gets the signal a while after it is sent. If you are receiving several such signals, you can compare the given times to find the distance to each satellite. Now you can do trigonometry on the satellites' positions to find your own position.
