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– Representation
– A viewshed can be represented by raster data indicating visibility.
– Binary representation shows visibility with values of 1 (true) or 0 (false).
– Visibility in certain disciplines like radio communications may be probabilistic.
– Viewsheds for multiple points, lines, or areas may have counts or fractional values.
– Queries can involve determining how much of a certain feature is visible.

– Viewshed and total-viewshed computation
– A terrain is represented using a Digital Elevation Model (DEM).
– Viewshed calculation on large DEMs is computationally costly.
– Total-viewshed refers to calculating viewshed for all points of the DEM.
– Faster algorithms have been proposed for computing total-viewshed of large DEMs.

– History
– Clifford Tandy coined the term viewshed in 1967.
– The term was used in the Oakland Tribune in 1970.

– Related concepts
– Viewsheds are a type of visibility graph.
– Isovists are a related concept common in architecture studies.
– Zone of Visual Influence refers to the area from which a structure is visible.
– Total-viewshed map shows the visible area in a DEM.

– Zone of visual influence
– It is the area from which a structure is theoretically visible.
– Represented using color maps to indicate visibility.
– Used in landscape architecture for visual intrusion assessment.
– GIS tools are utilized to create zones of visual influence.

Viewshed (Wikipedia)

A viewshed is the geographical area that is visible from a location. It includes all surrounding points that are in line-of-sight with that location and excludes points that are beyond the horizon or obstructed by terrain and other features (e.g., buildings, trees). Conversely, it can also refer to area from which an object can be seen. A viewshed is not necessarily "visible" to humans; the same concept is used in radio communications to indicate where a specific combination of transmitter, antenna, and terrain allow reception of signal.

Viewshed of the Gusev crater on Mars from the Mars Exploration Rover (red) overlaid on an elevation map (other colors) – areas in red are visible from the landing site

Viewsheds are commonly used in terrain analysis, which is of interest to urban planning, archaeology, and military science. In urban planning, for example, viewsheds tend to be calculated for areas of particular scenic or historic value that are deemed worthy of preservation against development or other change. Viewsheds are often calculated for public areas — for example, from public roadways, public parks, or high-rise buildings. The preservation of viewsheds is frequently a goal in the designation of open space areas, green belts, and community separators.

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