Basic Overlay Geoprocessing Tools in QGIS

Creating buffer or clipping the polygon it will be using the Geoprocessing tools to demonstrate some of the task that might use every day while editing.

• Creating Buffer:

You have to create buffer all the time, it is fixed distance around the polygon, polyline or point file. To do that open the tool from Vector → Geoprocessing Tools → Buffer. Then you assign the layer under Input layer, buffer distance and output file name and click ok.


For example: Building layer is used here as input vector layer.

• Intersect:

Intersect tools allow you to exclude the area that is not overlapping. To do that open the tool from Vector → Geoprocessing Tools → Intersect.


Assign Input Vector layer i.e. Building and Intersect layer i.e. Building Buffer and finally assign the output file name.

• Union:

Union allow to merge two layer into one layer but it does not remove the boundary line. To do that open the tool from Vector → Geoprocessing Tools → Union. You assign Input Vector layer i.e. Building Buffer and Union layer i.e. Building and finally assign the output file name. Attributes from both the layer are copied.

• Symmetrical Difference:

Symmetrical Difference is opposite to intersect, it removes area that is overlapping. To do that open the tool from Vector → Geoprocessing Tools → Symmetrical Difference. You assign Input Vector layer i.e. Building and Difference layer i.e. Buffer and finally assign the output file name. Attributes from both the layer are copied.

• Clip:

Clipping allows you to clip the feature with the defined boundary line. To do that open the tool from Vector → Geoprocessing Tools → Clip. You assign Input Vector layer that you want to clip and Clip layer that’s boundary line will be used to clip and finally assign the output file name. It is similar to intersection tools, only difference is input layer attributes are copied

• Difference

Difference layers allows to create area of input layer that is not overlapped. To do that open the tool from Vector → Geoprocessing Tools → Difference. You assign Input Vector layer that you want to create that is not overlapped (Buffer layer is used in example) and Difference layer that is overlapping some area of input layer (Building layer is used in example) and finally assign the output file name. Attribute table holds the values of input layer.

• Dissolve:

Dissolve layer is similar to union but in this everything is merged by the common field and it works on single layer. To do that open the tool from Vector → Geoprocessing Tools → Dissolve. You assign Input Vector layer ( Building layer is use in example) that you want to work on and dissolve field that is common and finally assign the output file name.