Today satellite based navigation systems are used for monitoring the location and movement of objects on the earth’s surface. It is used in several sectors like map making, transportation, etc. The most important among these is the Global Positioning system of the USA.
In this system, a series of 24 satellites placed at different orbits between the altitudes 20000 and 20200 km above the earth’s surface locate objects. We can locate places with the help of the signals received from the satellites in our handheld device. The GPS requires signals from atleast four satellites to display information like latitude, longitude, elevation, time, etc. This facility is now open to the public since 1980.
IRNSS is a satellite-based navigation system developed by India as an alternative to of GPS.
It has radius of 1500 km including India, Pakistan, China and the Indian Ocean. Of the 7 satellites planned, all have been launched.
