I'm fairly new to QGIS, and I'm trying to create a buffer around the outline of Spain (including the coastline and boarders). When I do so, it buffers all the country from center to the edge, I just need the edge if that makes sense.

the picture attached here shows the whole country, and I'd like to buffer the outline of it


3 Answers 3


For dissolving polygons for buffer, you can just check Dissolve result option in Buffer parameters:

enter image description here


You need to do the following:

  • Dissolve the detailed administrative boundaries based on a field in the attribute table that has same value
  • The output of the dissolve will have only one boundary that covers whole Spain.
  • Then you can use buffer to buffer the outline.
  • If you need only the mainland without considering the islands, then select the mainland and apply buffer on the selected feature.

The trick is to join all the polygons in your map together,

So given (for example) the GB constituencies:

enter image description here

You run dissolve (in the vector geometry menu of the processing toolbox) to give a single (multi)polygon:

enter image description here

Then you can buffer it as you want.

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