Global Positioning System (GPS)

Source– This post is based on the article “Understanding how the Global Positioning System (GPS) works” published in “The Hindu” on 5th December 2023.

Why in the News?

Global Positioning System (GPS), used for navigation, has had a revolutionary impact on our lives. From civilians to the military, from precision scientific studies to urban planning and disaster risk estimation, it has been crucial in various sectors.

What is GPS?

1) The U.S. Department of Defence started the GPS programme in 1973 and launched the first satellite in 1978.

2) GPS is a satellite-based navigation system based on a “constellation” of approximately 24 well-spaced satellites.

3) The 24 satellites move around the earth in six orbits, with each satellite completing 2 orbits in a single day. In this configuration, anyone on the earth will be able to ‘see’ at least four satellites at a time, which is a crucial requirement.

4) The overall programme has three main components — the space segment, the control segment, and the user segment.

How does GPS work?

1) Each GPS satellite continuously broadcasts a radio signal containing information about its location in orbit, operational status, and the time at which the signal is emitted.

2) Based on the information contained in this signal, the GPS receiver calculates its precise distance from the satellite.

3) Such calculations are made from the signals of four satellites which helps in accurately triangulating the location of the GPS receiver on the ground.

4) Time at which the signal is emitted from the satellite (and received by the GPS receiver on ground) plays a crucial role in calculating the distance. To ensure accuracy in timekeeping, each GPS satellite is equipped with an atomic clock that provides extremely accurate timekeeping.

What are other countries that have Global Navigation Satellite System?

1) Apart from GPS, Russia’s GLONASS, the E.U.’s Galileo, and China’s BeiDou are some other global navigational satellite systems.

2) India has its own regional navigation satellite system called Navigation with Indian Constellation (NavIC) developed by ISRO. It consists of 7 satellites.

UPSC Syllabus- Science & Technology