GPS full form is a Global positioning system. It was first launched by the American AirForce and its official name is NAVSTAR GPS(Navigation Satelite Timing and Ranging System).
GPS is a US program and it is the most popular because it is free. Apart from this, Russia has GLONASS, China has BEIDOU, and European countries have GALILEO as their own GPS program.
At the time of the Kargil War, America refused to provide GPS to India. That is why India launched its GPS program called IRNSS (independent regional navigation satellite).
IRNSS launched 7 satellites and Its last satellite was launched on 12 April 2018.
History of GPS
GPS technology is a military invention. GPS first came when the cold war was going on between the US and China.
At that time the American defense system felt that how to keep information about their army and an intruder is coming in their border. So at that time, GPS needed.
Finally, in 1973, GPS was first made by American AirForce. But it was not yet available to the common people, after 10 years, in 1983, the GPS service was made available to the common people.
And gradually as 1995 came, by now GPS was being used globally and spread globally. Its first satellite launched in 1978 and with the launch of the 1995 last satellite, it started functioning fully.
Although it was opened for civilian use in 1980, it had a lot of limitations at that time. Gradually by the year 2000, it was fully opened for civilian use.
How does GPS work?
Each GPS device has a GPS receiver and this GPS receiver tells the recording location of the signal from three satellites. But this location is in the form of distance from the satellite. Which has practically no meaning.
The GPS device that found the signal extracts the distance of these three satellites in the form of your location as longitude and latitude.
How it calculates the exact distance
There is an atomic clock inside these satellites which is so accurate that even after 30000000 years, it gets a 1-second error. These satellites always run on a fixed point, meaning that there is no effect in its location.
This satellite keeps moving and spreading its signal continuously while moving. This signal has an exact time and location. This GPS device which also has a clock in it, this clock matches the recording time from any satellite.
When a satellite sent a signal, it captures it. Then it finds out how long the signal from the satellite reached here. Based on this time, it finds the distance equal to time divided by speed
Distance = Time/Speed of Signal(The speed of the signal is 299792458 M/s which is equal to the speed of the light)
Similarly, the GPS device detects the distance of three satellites and extracts the particular location.
The US has so far launched 72 satellites for GPS and 33 of them are in operation. This satellite, which revolves around the earth 2 times in a day