This technical note shows a process for overlaying two polygon vector layers. The layers used here are the tundra and swamp layers from the Alaska sample data set.
Plugins : fTools. This is a core plugin and should be installed by default.
To complete this process, first the two vector layers into QGIS. This example is using
<small>Alaska project showing tundra (purple) and swamp (grey)</small>
To open the union dialogue, select Vector → Geoprocessing tools → Union
<small>Union tool dialogue box</small>
Fill in the box, and be a little patient.
<small>Resulting shape file showing the union of the tundra and swamp data</small>
- using the select button, layers that are not open in QGIS can be used in this analysis.
- remember, that vectors can only display point, line or polygons.