Global Positioning System
GPS, of the Global Positioning System, is a system of satellites that orbit the earth above us that send signals continuously to ground stations that monitor and control GPS operations. GPS signals can be detected by GPS receivers, which by itself can calculate the location of the receiver by around ten metres. Such the accuracy and reliability of the GPS system that its is a required item for a long trip without and contact with humans.
The GPS system was originally intended for military use; its use was to track and detect ships and submarines by the US military in the 1960s. As time moved on, and as the development progressed, its use changed, from only a military use to a more civilian use. When the GPS system finally became operational in the 1990s, it has proven itself to be a very sophisticated tool, being very reliable, as shown by the usage of the GPS system by both military and civilians.
GPS worked by each satellite that emitted a unique radio wave also known as the Pseudo Random code', which is basically a series of random radio signals; so random, that there is absolutely no chance that thre would be a matching signal. The signals, which contain the time and the position of the satellite, are then compared by the GPS receiver from four satellites. Considering how extraordinarily sophisticated the technology is, the operating principle of GPS is remarkably simple. Each satellite continuously broadcasts a digital radio signal that includes both its own position and the time, exact to a billionth of a second. A GPS receiver takes this information--from four satellites--and uses it to calculate its position on the planet to within a few hundred feet. The receiver compares its own time with the time sent by a satellite and uses the difference between the two times to calculate its distance from the satellite. (Light travels at 186,000 miles per second: if the satellite time happened to be, for...