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