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I have a set of buildings in a polygon layer which I'm going to use in a 50k map. Since the buildings are tiny I cannot show the actual form of the building, instead I'm taking the centroid of the polygon and then make a point symbol (a square) which is a lot larger than the buildings original form.

When I do this in rural areas this is fine, but when there are a lot of tiny buildings near each other I have to do some kind of generalisation.

I have managed to remove smaller buildings that are in a certain distance from larger buildings (using buffer), but when I have a lot of buildings with the same size I'm not sure how to solve this.

Here are some images: original building polygons This image shows the original size of the building polygons

centroid point building symbols This image shows building symbols created from centroid of each building. As you can see this doesn't look good

the goal This is somewhat what I'd like to achieve. I have removed some of the buildings manually.

Any ideas?

I've seen that ArcGIS has a function called Simplify Building which is similar to whad I'd like to achieve. Unfortunately Open Source applications on OSX is the only possibility right now.

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It might be worth checking out GeOxygene. I believe that has various generalisation algorithms so there may be something for building aggregation or building displacement within that: http://sourceforge.net/projects/oxygene-project/ It is OpenSource but not for QGIS. I did used to have the OpenJump plugin for it installed, but not any longer so I can't check it out for you unfortunately.

Another option might be to try and improve the aesthetics of the results of your centroid method. Perhaps by using a line simplification algorithm on the polygon geometry. It won't look like your intended display but might communicate clusters of buildings sufficiently well for a 50k map. You could try using GRASS using v.generalize to do this and there maybe QGIS plugins too.

The aim would be to create a polygon areas representing clumps of buildings or the whole urban zone, rather than buildings. Bearing in mind this is 50k this might be OK.

  • I'll look into GeOxygene. Could you explain more what you mean about the other option? Simplify the geometries in order to get a little displaced centroids? – oskarlin Feb 5 '16 at 20:15
  • What I meant is use the output from your current method (the black polygons of image 2) within a line/polygon simplify routine. I thought maybe the main reason this is not aesthetically pleasing is the jagged boundaries. – Julian Rosser Feb 9 '16 at 10:51
  • I updated my other answer – Julian Rosser Feb 9 '16 at 10:58
  • The black objects aren't polygons. They are point objects which have the symbol of a black square! – oskarlin Feb 9 '16 at 15:16
  • Aha, I see what you mean now. Yes That's an option too actually. But most of the times these clusters are too small for using a settlement polygon I think. I think it would make people think it's more settlement than it is (just a few houses). – oskarlin Feb 9 '16 at 15:18

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