| Global Navigation Satellite System (GNSS) is the | | | | satellite navigation system was deployed by the |
| standard generic term for satellite navigation | | | | US defense forces in the 1960s. Transit's |
| systems that provide autonomous geo-spatial | | | | operation was mainly based on the Doppler Effect. |
| positioning with global coverage. It allows small | | | | By monitoring the shift of the frequency over a |
| electronic receivers to determine the location | | | | short time interval, it is possible for the receiver |
| including longitude, latitude and altitude to within a | | | | to determine the location to one side or the other |
| few meters using time signals transmitted by | | | | of the satellite, and several such measurements |
| satellite radios. The precise time for the reference | | | | combined with a precise knowledge of the |
| of scientific experiment is calculated by the | | | | satellite's orbit can fix a particular position. |
| receivers on the ground with a fixed position. | | | | The latest satellite navigation devices are more |
| The NAVSTAR Global Positioning System by the | | | | direct. They are capable of broadcasting a signal |
| U.S. is the only fully operational GNSS. Russia with | | | | that carries the position of the satellite and the |
| GLONASS is all set to enter into the field of | | | | precise time of the signal transmitted. The position |
| GNSS. The European Union's Galileo positioning | | | | of the satellite is transmitted in a data message |
| system belongs to the next generation GNSS in | | | | that is superimposed on a code that serves as a |
| the initial deployment phase, which is expected to | | | | timing reference. |
| be operational in 2010. The Beidou navigation | | | | The main purpose of satellite navigation devices |
| system by China is expected to get operational in | | | | are military applications. Satellite navigation allows |
| near future. IRNSS by India is in developmental | | | | for hitherto impossible precision in the delivery of |
| phase and is expected to be operational by | | | | weapons to targets, greatly increasing their |
| around 2012. | | | | lethality whilst reducing inadvertent casualties from |
| The history of satellite navigation devices traces | | | | misdirected weapons. |
| back to the cold war area. Transit, the first | | | | |