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Viewshed Calculations

A "viewshed" is a region visible to an observer. "Visibility" refers to line of sight, but the same concept and calculations apply to transmission of signals in other media: radio and microwave frequency waves, sonar, and radar.

Viewsheds can help answer many different kinds of questions:

  • How to situate infrastructure, such as pipelines and highways, in out-of-the way places that do not destroy the quality of natural scenery
  • Where to site transmission towers to avoid spatial gaps in reception
  • How to characterize regions under surveillance (or not under surveillance)

The simplest viewshed calculations suppose that light moves in straight lines in a Euclidean space (the earth is not curved and no refraction occurs). This is a good approximation for distances of several kilometers or miles. Corrections for the earth's curvature and for optical refraction in the earth's atmosphere are needed for accurate results over longer distances.

See Also