New Delhi: A satellite navigation (sat nav system) is a system of satellites that can help users determine the position of an enabled device anywhere on the earth’s surface to within a few hundred metres. The same system with global coverage may be termed a global navigation satellite system or 'GNSS'. The receiver picks up signals transmitted by navigational satellites. With satellite navigation, it is easi to trace location and is often helpful for users to find directions.
Currently, the United States NAVSTAR Global Positioning System (GPS) and the Russian GLONASS are the fully globally operational GNSSs. But of late, a Russian rocket launched the first two satellites of the European Union's Galileo navigation system after years of delay in an ambitious bid to rival the ubiquitous American GPS network. There are also other satellite navigation systems under development in different countries. Here's an overview of the different satellite navigation systems:
Global Positing System (GPS): The United States' GPS is operational since 1978 and is globally available since 1994. It is currently the world's most used satellite navigation system. Maintained by the United States government, it is freely accessible by anyone with a GPS receiver.
GLONASS: It is a satellite navigation system operated for the Russian government by the Russian Space Forces. The development of GLONASS began in the Soviet Union in 1976. Numerous rocket launches added satellites to the system until the "constellation" was completed in 1995. Following the completion, the system fell into disrepair with the collapse of the Russian economy. It was later recovered and restored in 2011, enabling full global coverage.
Galileo: Galileo is Europe's own global navigation satellite system, providing accurate global positioning service under civilian control. On October 21, 2011, the first two satellites designed to validate the Galileo concept were launched. The system will start operating in 2014 as a free consumer navigation service, with more specialised services to be rolled out until 2020, when it should be fully operational.
Compass: The People's Republic of China is in the process of expanding its regional Beidou navigation system into the global Compass navigation system by 2020. China started building its satellite navigation system to break its dependence on the US Global Positioning System (GPS) in 2000. The network is expected to provide global services by 2020.
GAGAN: India is also working on its own regional navigation system - GAGAN (GPS aided geo augmented navigation). The system being developed by Indian Space Research Organisation (ISRO), would be under the control of the Indian government. The government approved the project in May 2006, with the intention to complete and implement it by 2014. It is said to have a constellation of seven navigational satellites. The satellites will also offer seamless navigation to air traffic over the Indian Ocean and the Indian airspace.
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