History of GNSS (Finding Positions from Using Celestial Bodies to GPS NAVSTAR, TRANSIT, & NAVSAT) (Especially for GATE-Geospatial 2022)

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GNSS

In this section, we shall discuss about the history of GNSS. Leaving stones, marking trees or referencing mountains were some of the ways used by early humans for finding their locations.

  • With the discovery of constellations, the relative positions of Sun, Moon and Stars were considered as point of reference.
  • With the advancement of communication technology, radio signals were used for finding location by measuring time taken for special radio signals.
  • The primitive navigation system which is known as LORAN (Long Range Navigation) was developed in early 1940s by USA. It became operational in 1943.
  • LORAN was the first radio navigation system that provided aid to the marine radio navigation.
  • It was based on the principle of time difference between the receipts of signals from a pair of radio transmitters. It covered only 5 % of the Earth՚s surface and just provided 2 dimensional information (latitude and longitude) with accuracy up to 250 m.
  • During the early 1960s, the importance of GNSS was first realized by the US Department of Space. As a consequence, several US Government agencies started putting efforts for designing and developing satellite system for the determination of three dimensional positions.
  • The result of such efforts led to the development of navigation system named Omega.
  • It became operational in 1971 and was shut down in 1997. It was the first radio navigation system for the aircraft which was operated by US in cooperation with six partner countries such as Argentina, Norway, Liberia, France, Japan and Australia.
  • It enabled ships and aircraft to determine their position by receiving very low frequency radio signals.
  • During the same time US developed and deployed first satellite based navigation system known as TRANSIT.
  • This system is also known as NAVSAT (Navy Navigation Satellite System) because it was primarily used by U. S. Navy for determining accurate location information.
  • TRANSIT provided continuous navigation satellite service from 1964 to 1996 initially for Polaris submarines and later on for civilian usage. It was also used for geodetic and hydrographic surveying.
  • The advent of GPS made TRANSIT as an obsolete system. As a consequence, its navigation service ceased in 1996. The swift growth in civilian use of GNSS took place only twenty years ago which was limited to merchant ships՚ crews and surveyors.
  • The major breakthrough came with the introduction of American NAVSTAR, more commonly known as GPS. The roots of GPS are closely connected to the launch of the Sputnik satellite by the former Soviet Union in 1957. But a modern GPS came into existence in 1973 when US Department of Defence decided to develop satellite navigation system based on its previous systems like TRANSIT. When the first satellite was launched in 1978, the GPS was only intended for US military applications.
  • Today, millions of GPS receivers are being used in transport, commerce and variety of recreational activities. In mid 1980s, the system was made available for civilian uses especially in aviation industry.
  • By 1994, a complete constellation of 24 satellites was in orbit initiating the GPS system՚s full operational capability.

The ‘Cold War’ rivalry between the USA and the former Soviet Union led to the ‘Space Race’ and almost parallel development of GLONASS − the Soviet system.

Developed by: