171:. Viewsheds and isovists are sometimes said to be equivalent, however others have found differences between them. It has been argued that isovists are more focused on representing space whereas viewsheds are about the visibility of features. Also, the problems they are used in have different scales. Planners use viewsheds where terrain heights come into play whereas architects do not typically take that into account with isovists.
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74:. 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 â for example, from public roadways, public parks, or high-rise buildings. The preservation of viewsheds is frequently a goal in the designation of
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Viewshed calculation on a large DEM is costly from a computational point of view. This cost is much higher when calculating the viewshed for all the points of the DEM, also called total-viewshed. A faster algorithm for computing the total-viewshed of large DEMs was proposed on.
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and therefore the viewshed may be represented with non-integer values. Viewsheds for multiple points, lines, or areas may have counts or fractional values for queries involving "how much" or "how many" (e.g., how much of a highway is visible?).
102:) with a value of 1 (or "true") indicates that the viewpoint is visible from that cell, while a value of 0 (false) indicates that the viewpoint is not visible. In certain disciplines, such as radio communications, "visibility" may be
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A terrain can be represented using a regular grid of points called
Digital Elevation Model (DEM). Where each point of the DEM is represented by its coordinates X, Y and its height Z.
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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 "
284:. Washington, DC: U.S. Department of Transportation, Federal Highway Administration, Office of Environmental Policy. September 1990. pp. 26â33, 123.
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is the area from which a development or other structure is theoretically visible. It is usually represented as a map using color to indicate visibility.
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Cervilla, A; Tabik, S; VĂas, J; MĂ©rida, M; Romero, F (2016). "Total 3Dâviewshed Map: Quantifying the
Visible Volume in Digital Elevation Models".
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that are visible from a particular area. A cumulative zone of visual influence is used to define the cumulative effects of many developments.
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Zones of visual influence are used to identify the parts of a landscape that will be affected by a development. They are of particular use to
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Tabik, S; Cervilla, A; Zapata, E; Romero, F (2015). "Efficient data structure and highly scalable algorithm for total-viewshed computation".
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indicating the visibility of a viewpoint for or from an area of interest. In a binary representation, a cell (shown graphically as a
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Total-viewshed map refers to the map, where each point represents the number of KmÂČ visible at that point in the DEM.
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to indicate where a specific combination of transmitter, antenna, and terrain allow reception of signal.
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is the geographical area that is visible from a location. It includes all surrounding points that are in
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The 3D-viewshed of a point (X,Y) of the DEM consists of the visible space from that point.
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Wind Energy - The Facts: "A Guide to the
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IEEE Journal of
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Association, European Wind Energy
European Wind Energy (2012-05-04).
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Nijhuis, Steffen; van
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are a closely related concept that is more common in the study of
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The area from which a structure can be seen may be called the "
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with that location and excludes points that are beyond the
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development. A map will be created showing the number of
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559:Morris, Peter; Therivel, Riki (2009-03-05).
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286:Publication number FHWA-HI-88-054.
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441:Weitkamp, Gerd (September 2011).
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610:Environmental impact assessment
205:environmental impact assessment
58:Viewsheds are commonly used in
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257:Euclidean influence zone
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176:Zone of Visual Influence
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139:. The lexicographer
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594:Categories
375:"viewshed"
263:References
76:open space
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384:March 10,
209:wind farm
136:watershed
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329:23232474
226:See also
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453:: 208.
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237:Isovist
222:tools.
129:History
78:areas,
49:visible
45:horizon
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282:(PDF)
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567:ISBN
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