In addition, users can choose to dissolve or not dissolve the boundaries between overlapping, coincident buffer areas. Variable width buffers Regions of variable width around points, lines, or polygons., on the other hand, call on a premade buffer field within the attribute table to determine the buffer width for each specific feature in the dataset ( Figure 7.2 "Additional Buffer Options around Red Features: (a) Variable Width Buffers, (b) Multiple Ring Buffers, (c) Doughnut Buffer, (d) Setback Buffer, (e) Nondissolved Buffer, (f) Dissolved Buffer"). require users to input a value by which features are buffered ( Figure 7.1 "Buffers around Red Point, Line, and Polygon Features"), such as is seen in the examples in the preceding paragraph. Constant width buffers Regions of constant width around points, lines, or polygons. Two primary types of buffers are available to the GIS users: constant width and variable width. If no features are selected, all features will be buffered. For example, the buffer tool will typically buffer only selected features. Several buffering options are available to refine the output. In either case, the use of buffers provides a quick-and-easy tool for determining which areas are to be maintained as preserved habitat for the endangered fly.įigure 7.1 Buffers around Red Point, Line, and Polygon Features In this case, he or she could create a 1,000-foot buffer around all polygons labeled as “Delhi Sands” on a soil formations dataset. Alternatively, the manager may decide that there is not enough point-specific location information related to this rare species and decide to protect all Delhi Sands soil formations. To accomplish this task, a 1,000-foot protection zone (buffer) could be created around all the observed point locations of the species. This species is found only in the few remaining Delhi Sands soil formations of the western United States. For instance, suppose that a natural resource manager wants to ensure that no areas are disturbed within 1,000 feet of breeding habitat for the federally endangered Delhi Sands flower-loving fly ( Rhaphiomidas terminatus abdominalis). Geoprocessing usually involves the input of one or more feature datasets, followed by a spatially explicit analysis, and resulting in an output feature dataset.īuffers are common vector analysis tools used to address questions of proximity in a GIS and can be used on points, lines, or polygons ( Figure 7.1 "Buffers around Red Point, Line, and Polygon Features").
is a suite of tools provided by many geographic information system (GIS) software packages that allow the user to automate many of the mundane tasks associated with manipulating GIS data. Geoprocessing Any operation used to manipulate spatial data. Buffers are particularly suited for determining the area of influence around features of interest. is the process of creating an output polygon layer containing a zone (or zones) of a specified width around an input point, line, or polygon feature. Buffering Placing a region of specified width around a point, line, or polygon.