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.
<p>
The plugin requires GEOS support compiled into PostGIS and the GEOS library
must be installed (see <ahref="http://geos.refractions.net">
http://geos.refractions.net</a> for details).
<p>
<h3>Settings</h3>
<center>
<imgalt=""src="bufferdialog.png"><p>
</center>
The options available in the buffer dialog are described in the table below.
<center>
<tablecellpadding=4border=1>
<tr><th>Setting</th><th>Explanation</th></tr>
<tr><td>Buffer distance in map units</td><td>The size of the buffer</td></tr>
<tr><td>Table name for the buffered layer</td><td>This name will be used when creating the buffered layer in the database</td></tr>
<tr><td>Spatial reference ID</td><td>The id from the spatial_references table that describes the coordinate system of the data</td></tr>
<tr><td>Geometry column</td><td>Name for the column to store the geometry for each buffered feature</td></tr>
<tr><td>Unique field to use as feature id</td><td>Name of the field to use as the primary key for the buffered layer. Select a field name from the list or choose <i>Create unique object id</i> to have the plugin create a primary key field</td></tr>
<tr><td>Schema</td><td>Choose the schema to use in creating the buffered layer. Only existing schemas are displayed in the drop-down box</td></tr>
<tr><td>Add the buffered layer to the map?</td><td>Checking this option will cause the buffer layer to be added to the map after processing is complete</td></tr>
</table>
</center>
<h3>Howto</h3>
To create a buffer:
<ol>
<li>Start QGIS
<li>Add a PostgreSQL/PostGIS layer (this example uses the Alaska layer)
<br>
<imgalt=""src="alaska_pglayer.png"><p>
<li>Select the layer by clicking on it in the legend
<li>Select Tools|Plugin Manager from the menu
<li>From the Plugin Manager, click the box to the left of the Geoprocessing plugin
<br><imgalt=""src="pluginmanager.png"><p>
<li>Click Ok to load the plugin
<li>A new menu (Geoprocessing) is added to the menu bar and a Buffer icon is added
to the toolbar.
<li>Click on the Buffer icon <imgsrc="buffericon.png"align="absmiddle"> in the toolbar
<li>The Buffer dialog appears. Set the buffer distance to the desired size (example 1000)<br>
<imgsrc="buffer.png">
<li>Clicking the <i>Add buffered layer to the map?</i> 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
