Specify distance buffers¶
Buffer operations will result in (multi)polygons that cover all areas that are closer to the input feature geometry than the given buffer distance(s).
The buffer tool (under Vector-> Geoprocessing Tools, and under Vector Geometry Tools in Processing) offers two buffer variants:
- Buffering with a user provided buffer distance (given in the Buffer distance field).
For polygon layers, a negative value can be used to remove the outer part of the polygons (to buffer inward).
- Buffering based on the values of an attribute (selected in the Buffer distance field chooser).
Each feature geometry will be buffered using its value for this attribute.
For both variants, the accuracy of the buffer can be specified using the Segments to approximate field. A larger value will give a better approximation of the buffer, but will require more processing time. Segments to approximate specifies the number of segments to use to approximate a quarter of a circle.
By choosing Dissolve buffer results, the polygons resulting from the buffer operation are merged to form a single multipolygon.
Both GRASS and SAGA offer Buffer operations that are available in Processing. SAGA has some interesting options (Arc Vertex Distance and Number of Buffer Zones).
The Multiple Distance Buffer Python plugin can be used to create multi-distance buffers (also called multiple buffer zones / multi-ring buffers).
The user specifies the buffer distances.
The resulting dataset consists of non-overlapping multipolygons (one for each buffer distance). The distance attribute gives the buffer distance for each multipolygon.
In Processing, SAGA offers multi-distance buffers with zones of equal width (the Number of Buffer Zones option).