Satellite Navigation - Understanding Satellite Navigation Technology
Satellite navigation is a broad term for Global Navigation Satellite System. It allows small electric receivers to determine their location such as the longitude, latitude, and altitude to within a few meters through radio signals transmitted along a line of sight from orbiting satellites.
Since the 1960s, the United States military has a constellation of satellites used by the military to help determine the positions of ships, airplanes, and personnel. To update high tech weaponry which most ships carry and to determine their location, the United States Navy has a particular need of extremely accurate navigation system. For this very reason the Transit, Timation, and Nova systems were built and placed in orbit. Later on as technology progressed, a more accurate system known as the Global Positioning System GPS or NAVSTAR was sent to orbit. This constellation of satellites are currently used by infantry soldiers who can determine their location accurately making map reading more reliable than without the use of Global Positioning System. Aircrafts can now fly anywhere in the world without the use of conventional navigation equipment and can determine their location within a hundred feet.
Before the use of satellites, early predecessors of navigation systems were using land-based longwave radio transmitters. These land-based navigation systems are the LORAN, DECCA, and Omega systems. These systems send out a radio broadcast from a master location which is then followed by pulses from various “slave” stations. The delay between reception and transmission can be calculated to get the distance between each of the slaves, thus providing a fix.
Satellite navigation’s original motivation was for military applications. It allows impossible precision in the delivery of weapons to targets, reducing accidental casualties from misdirected weapons, and making them even more lethal. It is also used to direct forces and locate them more easily reducing the level of unclarity in situational awareness experienced in military operations. It has also civil uses such as trekking using hand-held devices to directing traffic for cars, trucks, ships, and aircraft. Satellite navigation systems are also used for location-based services such as enhanced 911 search-and-rescue operations, surveying, data entry for geographic information system, geophysical sciences, and tracking wildlife.
There are only two current global navigation systems. The Global Positioning System is owned by the United States and is the only fully functional, fully available global navigation satellite system. It has six different orbital planes and involves thirty-two medium satellites. It has been operational since 1978 and is currently the most utilized satellite navigation system in the world. The other one is the GLOSSNASS which is owned by the Soviet Union now known as Russia. It is a constellation of fully functional navigation satellites but since the collapse of Soviet Union, the satellites have been damaged and has not been repaired leading to gaps in its orbital coverage and partially available. It is expected to return to full global availability in the future with the help of India who is helping in the restoration of these Russian satellite navigation systems.