Sat Nav Or GPS Devices

Global Navigation Satellite System (GNSS), is the standard generic term for satellite navigation devices that provide autonomous geo-spatial positioning with global coverage. The GNSS with the help of time signals transmitted along a light of sight by radio allows small electronic receivers in determining the location. Receivers placed on the ground with a fixed position also help in calculating the precise time as a reference for scientific experiments.

Until 2007, NAVSTAR Global positioning Systems was the only fully operational GNSS. Russia with its new GNSS, the Russian GLONASS, is under process of getting into full operation. Galileo Positioning System, the GNSS from European Union. is another satellite navigation device which is expected to get operational by 2010. China is also planning to expand its regional Beidou navigation system into a global system. India is another country that is planning to join the race by developing IRNSS, a next generation GNSS is in the developmental phase and is scheduled to be operational around 2012.

“Transit,” by the U.S. military was the first satellite navigation system deployed in the 1960s. The operation of Transit was based on the Doppler effect; the satellites traveled on well-known paths and broadcasted their signals on a well known frequency. The received frequency may slightly differ from the broadcast frequency due to the movement of the satellite with respect to the receiver. With the monitoring of this frequency shift over a short time interval, it is possible for the receiver to determine its location to one side or the other of the satellite, and several such measurements, combined with a precise knowledge of the satellite’s orbit, can fix a particular position.

The original aim of the development of satellite navigation devices was military applications. Satellite navigation helps for hitherto impossible precision in the delivery of weapons to targets, greatly increasing their lethality whilst reducing inadvertent casualties from mis-directed weapons.