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OPERATIONS ON EXTENDED NEIGHBORHOODS Distance calculate the distance of each cell from a cell or the nearest of several cells o each pixel's value in the new layer is its distance from the given cell(s) Buffer zones buffers around objects and features are very useful GIS capabilities o e.g. build a logging buffer 500 m wide around all lakes and watercourses buffer operations can be visualized as spreading the object spatially by a given distance the result could be a layer with values: 1 if in original selected object 2 if in buffer 0 if outside object and buffer applications include noise buffers around roads, safety buffers around hazardous facilities in many programs the buffer operation requires the user to first do a distance operation,
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Unformatted text preview: then a reclassification of the distance layer • the rate of spreading may be modified by another layer representing "friction" o e.g. the friction layer could represent varying cost of travel o this will affect the width of the buffer - narrow in areas of high friction, etc. Visible area or "viewshed" • given a layer of elevations, and one or more viewpoints, compute the area visible from at least one viewpoint o e.g. value = 1 if visible, 0 if not o useful for planning locations of unsightly facilities such as smokestacks, or surveillance facilities such as fire towers, or transmission facilities...
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