This unique addition to reference literature provides an introduction to the major concepts and contemporary issues that are essential for students of environmental science and environmental studies to know. With over 200 entries authored by world-class names like Anthony Brazel, John Day and Edward Keller, this text is divided into six sections: Environmental Science, Environments, Paradigms & Concepts, Processes & Dynamics, Scales & Techniques, and Environmental Issues.  

Global Positioning Systems (GPS)

Global positioning systems (GPS)

The Global Positioning System (GPS) is a navigation system that uses a constellation of 24 satellites placed into orbit by the US Department of Defense.

First launched into orbit in 1978 by the US Department of Defense (USDoD) for its exclusive use, the system became fully available for international public use in 1994. The ‘man-made stars’ circle 20,000 km above the Earth at about 11,000 km per hour, twice a day in very precisely determined orbits, and they continuously transmit signal information back to Earth. GPS works anywhere in the world, in all weather conditions, 24 hours a day. The signals travel by line of sight, so that they pass through clouds, glass, and plastic, but they cannot go through ...

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