The Global Positioning System

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The Global Positioning System The global positioning system (GPS) is a satellite-based navigation system, consisting of a network of 24 orbiting satellites travelling on six different orbital paths. These satellites, referred to as NAVSTAR satellites, are constantly moving, making two complete orbits around earth per day. The first GPS satellite was launched in February, 1978. Satellites now weight approximately 1 tonne, and are about 5 metres across with extended solar panels. GPS needs at least 24 satellites to provide full coverage of every point on the earth, all the time. To calculate one position on the earth, at least 3 satellites are needed. Currently, there are 28 working GPS satellites, out of roughly 750 currently in miliary, civilian and commercial use. GPS satellites, quite simply, broadcast data - each satellite knows two things: its exact location in obit, and exactly what time it is. It knows its position within a few feet, whilst moving a t 17 000 miles per hour, and knows the time within approximately 100 picoseconds (1 trillion picoseconds to a second). The satellite signal also contains a 'psuedo-random code' - its identification, ephemeris and almanac data. Ephemeris data contains the status of the satellite (able to function or no), the information mentioned earlier, that is the current date and time. The almanac data tells the GPS receiver where the GPS satellite should be at any time throughout the day. Each satellite transmits data not only on its own location, but the location of every other satellite in the system. To condense this, each satellite transmits a message which informs of i... ... middle of paper ... ...en, how far, how fast, and can bill you for the risks that you're taking. A trial has already been performed in Texas using such a system. Indeed, commercial companies are now using GPS for ultimate knowledge - knowing exactly where their units are, and what they are doing, in the mould somewhat, of Big Brother. Big Brother-esque again, is the fitting of GPS chips into mobile phones. By the end of 2005, all mobile phones sold in the US must be able to report their location. The GPS phone will know where it is and be able to report that information, if it is stolen, in an emergency, if you are lost. Further GPS research can only further the dominance of this technology, providing a future with greater awareness, greater knowledge, openness and even wider communication, making the world once more a smaller place.

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