A union turns two overlapping shapes into one. This task can be easily accomplished with the Processing Toolbox. In this recipe, we'll merge the outline of a covered building with the footprint of the main building.
You can download the building files from https://geospatialpython.googlecode.com/svn/union.zip and extract them to a directory named /qgis_data/union
.
All we need to do is run the qgis:union
algorithm, as follows:
Start QGIS.
From the Plugins menu, select Python Console.
Import the
processing
module:import processing
Now, run the algorithm by specifying the two input shapes and a single output file:
processing.runandload("qgis:union","/qgis_data/union/building.shp","/qgis_data/union/walkway.shp","/qgis_data/union/union.shp")