Accuracy And Reliability Of The Gps System example essay topic

Physics Assignment 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 metre's. 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 1960's. 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 1990's, 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 example, one-thousandth of a second behind the GPS receiver's time, then the receiver would calculate that it was 186 miles from that satellite.) By checking its time against the time of three satellites whose positions are known, a receiver could pinpoint its longitude, latitude, and altitude. The method just described would require that both the satellites and the receiver carry clocks of remarkable accuracy. However, having a receiver pick up a signal from a fourth satellite allows the receiver to get by with a relatively simple quartz clock -- like that used in most watches. Once the receiver has made contact with four satellites, the system takes over and computes its position almost instantaneously.

For the system to work, the receiver has to know exactly where the satellites are and the satellites have to be able to keep reliable and extraordinarily accurate time. Accuracy is ensured by having each satellite carry four atomic clocks, the most accurate timing devices ever made. Reliability is ensured by the satellites' 11,000-mile-high orbits, which put them far above the atmosphere and keep them moving in very predictable trajectories. The Department of Defense monitors the satellites as they pass overhead twice a day and measures their speed, position, and altitude precisely. That information is sent back to the satellites, which broadcast it along with their timing signals.

Currently, there is research upon GPS technology by the Satellite Navigation and Position group (SNAP) on Remote Sensing Based upon Indirect GPS signals. It is about improving GPS technology so it can position the person with greater accuracy than before, and the evaluation of the system upon remote sensing tasks. It will be a great boon to the wider community as it would make GPS more reliable and accurate, making rescues for stranded people faster, saving lives.