Polygon Outlines in QGIS

I had an effect of an outline around the grid in the Glasgow Commercial Property Density heatmap. I really like the effect, but to create it I had to save the grid itself as a new file, dissolve it and then symbolise it. There should be a way to do it simply through symbology. When working on some categorised symbology I though symbol levels would be the way to do it, and QGIS 2.6 actually made it possible.

I am not a huge fan of how QGIS deals with polygon boundaries, shared boundaries usually become thicker than non-shared boundaries. But we can still achieve some really good outputs.

We will start out with a simple categorised symbology.


I would like to remove the borders, but that results in very small gaps. We can tell by turning the project background black.


So I will set a narrow white border, which is very unintrusive.


Now for the QGIS 2.6 touch. We can now turn a graduated symbology into a rule based one, simply set up a graduated symbology and then select rule based and your rules will be automatically generated.


For the border we create a catch-all rule that has our desired border.


Resulting in.


But then setting up our symbol levels.


We get the desired result.


Final output.

QGIS Polygon Borders

Desired result with one dataset, excellent.