GPS (Global Positioning System) - The GPS is a Global Navigation Satellite System that transmits signals allowing receivers to determine the receiver's location, speed and direction. At first the GPS system was designed for and operated by the US military, and while it still is operated by them, the GPS system is used world-wide. GPS technology helped the U.S. Air Force take out al-Qaeda leader Abu Musab Al-Zarqawi in a June 14 airstrike.
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(see full article at: http://mg.gpsworld.com/gpsmg/article/articleDetail.jsp?id=364330)
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GPS works using a method called triangulation. Using only two sattelites, and some basic geometrical equations it is possible to calculate the exact location of GPS units on the earth. The calculation becomes increasingly accurate as more satellites are involved.
(http://www.how-gps-works.com/faq/q0110.shtml)

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Today, GPS is funded by and controlled by the U. S. Department of Defense (DOD). The cost of maintaining the satellite system is approximately $400 million per year, including the replacement of aging satellites. The satellites are a sort of "man made constellation," called a GPS Nominal Constellation, which consists of 24 satelittes in 6 orbital planes with 4 satellites in each, which orbit the earth in approximately 12 hours. There are often new satellites launched into orbit to replace the old ones, thus causing there to actually be more than 24 in orbit at a time. (article: http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html)
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GPS is free for civilian use as a public good. Now more and more companies are coming up with products to utilize the GPS, such as phone companies that put GPS into their products so that parents can keep track of their children so they know at all times where they are. Another common use now is GPS devices in cars to help people navigate around roads and highways.


Applications



Today there are many uses for the GPS system. GPS is integrated in to various devices in order to secure accuracy, easy, navigation, and safety.

  • GPS navigation devices are becoming more and more prevalent in automobiles. Many, especially luxury vehicles, come with these road navigation devices preinstalled. There is also a growing marked for aftermarket devices as well. They rely on preloaded maps and locations as well as the positioning of the GPS to remain as reliant and accurate as possible.
  • Both aircraft and boats also use various forms of GPS navigation systems. While all systems are useful in Navigation there are other uses for the system. Many maritime GPS units hold the ability to mark any location. This is useful to find a underwater location or of an overboard member, this can be a godsend when out in open water where markers like trees or roads cannot be used to pinpoint a location.
  • Hikers and climbers can acquire hand help devices that allow them to navigate thee terrain in much the same way. However and perhaps more importantly, devices can use the GPS system to aid in locating and rescuing any stranded or lost outdoorsman. Even with a less than pin point accuracy a GPS distress beacon can quickly narrow a search.
  • Commercially the GPS system can be used to aid in the organization and execution of tasks such as harvesting or crop dusting. Also the blades and buckets of construction equipment are controlled automatically in GPS-based machine guidance systems.
  • There are even companies that seek to increase the independent and mobility of the visually impaired using the GPS system. This system works much like the navigation systems of a car but uses cellular technology to create a text-to-speech form of directions.