GPS (Global Positioning System)
The first generation of the GPS was introduced in the year 1973 by US Department of Defense (USDOD) for finding the lost soldiers and to instantly calculate the math required to launch the missile. GPS started in 1989 with the launch of the first GPS. GPS became public in the year 2000. The GPS network is made up of 24 operational satellites and extras for backup, located nearly above 20,000KM above the earth’s surface. Satellites are placed around the earth in such a way that at any point of time the receiver will be receiving the signal from the four satellites. Each satellites rotates earth’s orbit in 11hr and 58minutes.
GPS satellites are also known as “NAVSTAR satellites”. There’re different types of navigational satellite system sent above by many countries across the world. But the most popular and commonly used one is NAVSTAR, which is launched by USA. However there’re Russian (GLONASS), Indian (IRNSS), Chinese (Bei-Dou-2) & European (GALILEO), out of which Indian system and Chinese system are below GEOSYNCHRONOUS Orbit which means they’re not worldwide system.