Buffer

The Buffer spatial operation generates buffer zones (or zones of influence) around the geometry of objects of a layer, considering a predefined distance. The figure bellow shows examples of buffer zones around a river or an municipality.

If the geometry of the objects are polygons it is possible to ask for internal and/or external buffers, as can be seen in the next figure.


Inside and outside buffer	Only outside buffer	Only inside buffer

It is possible to ask for several levels of buffers. Selecting a distance d and n levels will result in n buffers each at a distance d*(n-1). The next figure shows an example of buffers at multiple levels.

As the buffers around different objects might overlap, it is possible to request the dissolving of the boundaries inside the overlapping areas. This is illustrated in the next figure.

Interface usage

Go to Vector Processing > Buffer... to obtain the following interface:

Select the layer that contains the input objects.

Select "Fixed at" and inform a buffer distance that will be applied to all objects. This value must be in the same SRS unit of the input layer.

In the division "Rule for polygons", select the generation of inside and/or outside buffers (valid only for objects with polygon geometries.

In the division "Boundaries between buffers", select if overlapping buffers should be dissolved (default behavior) or not.

In the division "Multiple levels", select the number of buffer levels (default 1).

Select a layer name and a repository (data source) to store the operation result.

Click "OK" to perform the operation or "Cancel" to close the interface.

Usage tips

The buffer result can be stored in different TerraLib datasources. Check data source selector for more details on how to select a data source.

The option to use only selected objects from the Input layer is under development.

The option to use buffer distance for each object based on one of its attributes is under development.