Viewshed Analysis Using Point Layer and DEM or TIN (GIS Applications) : Uses & Output (Especially for GATE-Geospatial 2022)

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A viewshed refers to the portion of the land surface that is visible from one or more viewpoints. The process for deriving viewsheds is called viewshed or visibility analysis.

Image Shows Example of Viewshed Analysis

A viewshed analysis requires two input data sets. The first is usually a point layer containing one or more viewpoints such as a layer containing communication towers. If a line layer such as a layer containing historical trails is used, the viewpoints are points that make up the linear features. The second input is a DEM or a TIN, which represents the land surface. Using these two inputs, viewshed analysis can derive visible areas, representing, for example, service areas of communication towers or scenic views from historical trails.

Viewshed Analysis Uses

A viewshed analysis can be used for other applications. For example, a viewshed analysis could estimate the impact of the addition of a large building. The viewshed analysis would show all the areas from which the building could be seen as well as any views that would be obscured from any particular location. Viewshed analyses also used to locate fire observation stations in mountain areas.

Picture Shows Viewshed Map from National Historic Trails in …

An example of using a viewshed analysis on a line segment is from the Wyoming State Office, Bureau of Land Management, in which the office used a viewshed analysis to determine the visibility from National Historic Trails across Wyoming.

Output from Viewshed Analysis

The output of a viewshed analysis is a binary map showing visible and not visible areas.

Given one viewpoint, a viewshed map has the value of 1 for visible and 0 for not visible.

Given two or more viewpoints, two options are common for presenting the output. The first option uses counting operations. The second option uses Boolean operations. A viewshed map based on two or more viewpoints is often called a cumulative viewshed map.

Cummulative Viewshed Map

In figure, two options for presenting a cumulative viewshed map: the counting option (a) and the Boolean option (b) .

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