Have your ever wondered how your being located in your smartphones? How did Google trace out your location? Well, that’s our topic today.

What is GPS and GPS receiver?


stands for Global Positioning System. A GPS receiver
is nothing but an electronic device that receives GPS signals from satellites , that revolve around the earth in its orbit.

How many GPS satellites are available in the space?

There are totally 27 GPS satellites

in the space. Among the 27, 24 are used for locating and 3 are used as spare. So that if one of the satellites has a fault the spare ones can be utilized.

How do these GPS satellites locate us?

These GPS satellites use the concept of Trilateration. Let’s see a small example using a Venn diagram to understand this trilateration.

Venn diagram for Trilateration


  • Assume that you are the person A and you have two friends person B and C. You are unaware of your exact location.
  •  Now your mobile network gives you an approximation that you are located within this blue circle.
  •  You are contacting your friend B through mobile. His location is represented as a red circle.
  • Now you could notice that your range and your friend B ‘s range are intersected at two points say 1 and 2. This shows that you are located either at point 1 or at point 2.
  • Now you are contacting your friend C. His range is determined by green color.
  • Now your range and your friend C’s range are intersecting at point 1 and 3. This shows that you must be located at either point 1 or point 3.
  • Since 1 is a common point at both the cases, we conclude that you are at point 1.

This concept is called trilateration. Only by using this concept GPS satellites locates us.

If GPS is supposed to locate us, then how does it calculate our distance from surroundings?

This is so simple. Just by using the simple relation,

Distance = Speed x Time

These concepts are applications of relativity theory by Albert Einstein. Here is an another important discovery by Einstein‘s relativity theory.

These concepts are used in our android phones to locate us. They are used in maps to help in navigation, or send your location to our friend etc.

The concept and working of Global Positioning System are more clearly explained by Premanand Sethurajan in the following LMES video. Note; The video is available only in TAMIL.

Some of the other LMES videos are:

Kindly provide your feedback in the comments section.

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