PostGIS Buffer Plugin

QGIS PostGIS Buffer Plugin 0.1

Documentation

The buffer plugin creates a user specified buffer around features in a PostGIS layer. The results of the buffer operation are stored in a new layer in the PostgreSQL database.

The plugin requires GEOS support compiled into PostGIS and the GEOS library must be installed (see http://geos.refractions.net for details).

Settings

The options available in the buffer dialog are described in the table below.

Setting	Explanation
Buffer distance in map units	The size of the buffer
Table name for the buffered layer	This name will be used when creating the buffered layer in the database
Spatial reference ID	The id from the spatial_references table that describes the coordinate system of the data
Geometry column	Name for the column to store the geometry for each buffered feature
Unique field to use as feature id	Name of the field to use as the primary key for the buffered layer. Select a field name from the list or choose Create unique object id to have the plugin create a primary key field
Schema	Choose the schema to use in creating the buffered layer. Only existing schemas are displayed in the drop-down box
Add the buffered layer to the map?	Checking this option will cause the buffer layer to be added to the map after processing is complete

Howto

To create a buffer:

Start QGIS
Add a PostgreSQL/PostGIS layer (this example uses the Alaska layer)
Select the layer by clicking on it in the legend
Select Tools|Plugin Manager from the menu
From the Plugin Manager, click the box to the left of the Geoprocessing plugin
Click Ok to load the plugin
A new menu (Geoprocessing) is added to the menu bar and a Buffer icon is added to the toolbar.
Click on the Buffer icon in the toolbar
The Buffer dialog appears. Set the buffer distance to the desired size (example 1000)
Clicking the Add buffered layer to the map? will cause the layer to be added as soon as the buffer is complete. The buffered layer can also be added to the map using the Add a PostGIS toolbar button.