The great convenience that G P S take to our life
2008-07-30

                                                                                                         The great convenience  that G P S take to our life         The GPS System was created and realized by the American Department of Defense (DOD) and was originally based on and run with 24 satellites (21 satellites being required and 3 satellites as replacement). Nowadays, about 30 active satellites orbit the earth in a distance of 20200 km. GPS satellites transmit signals which enable the exact location of a GPS receiver, providing an exact geographic fix that can be plotted precisely on a map.          GPS have several characteristics as the followings: 24 Satellites(21 Active plus 3 spares) 6 Orbital Planes (Inclined at 55 Degrees) 20,200Kms above Earth’s Surface

12 Hour Orbit (In View for 4-5 Hours) Operate on GPS Time not Sidereal -Thus constellation in view 4 minutes earlier each day Designed to last 7.5 years Broadcast 2 Frequencies (L1&L2)          What GPS on earth can do for us? *Provide an exact geographic fix that can be plotted precisely on a map. *Tell you the straight-line distance and direction to your destination. *Record the day's travel as a "track," creating a highly accurate bread crumb trail you can reverse and follow home, or transfer to computer. *Provide detailed trip information, such as mileage, speed, and elevation gain. *Warn of topographical roadblocks like rivers and deep canyons, as long as you've loaded top maps onto the unit.             From what have being said above, we can see clearly GPS have so many functions, so which areas is it mainly being used? GPS is being used in aviation, nautical navigation and for the orientation ashore. Further it is used in land surveying and other applications where the determination of the exact position is required, including agriculture, oil, gas, mining and construction.            Without a reliable navigation system, military forces could not have performed so well in every war. GPS receivers were used in several aircraft, including F-16 fighters, KC-135 aerial tankers, and B-52 bombers. Navy ships used them for rendezvous, minesweeping, and aircraft operations. It has become important for nearly all military operations and weapons systems. It is also used on satellites to obtain highly accurate orbit data and to control spacecraft orientation.            The GPS system was developed to meet military needs, but new ways to use its capabilities in everyday life are continually being found. As you have read, the system has been used in aircraft and ships, but there are many other ways to benefit from GPS. We’ll mention just a few to give you an idea of its many uses.            Automobile manufacturers are also offering moving-map displays guided by GPS receivers as an option on new vehicles. The displays can be removed and taken into a home to plan a trip. Several major rental car companies have GPS-equipped vehicles that give directions to drivers on display screens and through synthesized voice instructions. Imagine never again getting lost on vacation, no matter where you are.            In China, GPS is helping to save lives and property across the nation. In this “5.12 Wenchuan earthquake”, China independently developed the "Beidou 1" system(GPS) in the disruption of communications circumstances play an important role in disaster relief forces to bring the “Beidou 1”system(GPS) are gradually returned and various disaster relief information.           The future of GPS is as unlimited as your imagination. New applications will continue to be created as technology evolves. GPS satellites, like stars in the sky, will be guiding us well in the 21st century.