Buffer (GIS)

From Wiki.GIS.com

In GIS, a buffer is a zone that is drawn around any point, line or polygon map feature that encompasses all the area within a specified distance of the feature. Buffer may also be used as a verb, as in "to buffer" a feature. Buffers are used to identify places at risk of impact from a specific point, line, or polygon feature. However, "negative buffers" may also be used for polygons to specify a distance inward from the boundaries of the area feature.^[1] A type of problem that a buffer would be required for is siting a landfill or power plant which must be a given distance away from homes and neighborhoods. A buffer would cover those residences at risk of a harm from a potential site. Buffers may be used for both raster and vector data model problems.^[2]

A buffer drawn around a point on a map.

A buffer drawn around a line on a map.

A buffer drawn around a polygon on a map.

Contents 1 Two Types of Buffers 1.1 Fixed Width Buffers 1.2 Variable Width Buffers 2 See also 3 References

[edit] Two Types of Buffers

There are two main types of buffers; fixed width buffers, and variable width buffers.

[edit] Fixed Width Buffers

The fixed width buffer is one of the most common buffers. A fixed width buffer is exactly as its name implies, a buffer that has a uniform unchanging width all the way around the object. This type of buffer is used with the assumption that the impact zone of the object being buffered has an equal impact all the way around itself. An example of this would be how far away from a stream or a river houses are allowed to be placed. Since laws may govern this, the distance doesn't change anywhere along the path of the stream.

[edit] Variable Width Buffers

Variable width buffers allow a varied width between the outside of the buffer and the object being buffered. This type of buffer takes into account variables that would cause the buffered zone around an object to be inconsistent. An example of when this type of buffer would be used is accounting for the fallout zone around a nuclear reactor being blown by the wind. In the event of an nuclear fallout, the wind could be blowing from east to west. The wind blowing the radiation to the west would cause the area to the west to have a much higher radiation hazard than the area to the east of the reactor. Buffering this area would show a very narrow buffer zone on the east side of the reactor, and a very elongated buffer zone to the west.

[edit] See also

• GIS Commons - Analysis > Neighborhood Operations > Buffering
• ArcGIS Desktop Help - Buffer (Analysis)
• ArcGIS Desktop Help - Buffer (Coverage)
• ArcGIS Desktop Help - Multiple Ring Buffer (Analysis)
• Geoprocessing

[edit] References