Union

The Union operation make an especial kind of union. It makes a intersection between the Input Layer and the Overlay Layer.

Where the layers intersects, it make a gometry with the difference between de Input Layer geometry with Overlay Layer geometry, a geometry with the intersection between both layers geometries and an other geometry with the difference between the Overlay Layer geometry and the Input Layer geometry.

With the layers attributes will work the same way, the first geometry will have only informations about the Input Layer, the secound geometry will receive the attributes of the Input Layer and the Overlay Layer and third gometry will receive only attributes of the Overlay Layer.

It is accessed through:

    Processing > Vector Processing > Union...

1. Select the Input layer to apply the union operation. 
2. Optionally check  Only Selected box to apply the union only over selected objects.
3. Select the Overlay layer to union with. 
4. Optionally check  Only Selected  box to apply the union only over selected objects.
5. Choose the attributes from both Layer changing to the right side.
6. Choose the Output Object Type, that define if the geoemtries will be grouped (Multi Geometry) or not (Single Geometry).
   
7. Inform the Output Repository by clicking on:
1. to select the output directory and also inform the new layer name to store the result, or
2.  to select the output Data Source.
8. Inform the new Layer Name to store the Union result, if the repository is a data source.
9. Click OK to perform the operation or Cancel to close the interface.

Usage tips:

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