I have 14 polygon layers. I have plotted them as transparent layers, so I can get a final layer with 6 different colours, which represent different categories. I want to create a new layer made by the 14 layers, but keeping the 6 different colours. The main problem is that the colours in the original layer aren’t attributes of the layers but that’s a single representation, so when I try to reclassify them or use the raster calculator, the final result is not useful at all. I have attached one image and the 14 transparent layers together, with the 6 different colours (light, medium and dark green and light, medium and dark red).

Someone knows how to get a single layer which allow to classify it in those 6 categories?

enter image description here

enter image description here

1 Answer 1


You have the union tag in your question all that is missing is adding an attribute for the colour you want to each layer before doing the union. The results will have a lot of spurious slivers. You say you have polygons but also that you are using raster calculator - a raster approach might be better but again you need to get your values sorted in the data rather than just how they are symbolised

  • Each layer has a colour associated with an attribute, but the main problem is that I get my final layer after overlay 14 transparent layers, which means that if I use the union tool, the resultant layer has 7053 polygons and it is very difficult to give them the correct colour. To use raster calculator I transformed polygons to rasterbut it didn’t work. Do you know how to add two colours per layer as an attribute? And, which tool can I use so when I overlay all layers, the resultant layer has not only the characteristic of the upper layer but the all layers that are below the last one?
    – Krahsin
    Commented Jan 4, 2015 at 18:54
  • I don't see how you are getting 6 colours when combining 14 layers. Some of the layers have the same colour ? if so it might be an idea to merge the layers that have the same attributes/ colours. Even then I don't get the mathematics. 2 colours gives 4 possible combinations and 3 gives 8.
    – Sethinacan
    Commented Jan 4, 2015 at 21:39
  • All the layers have the same colours (green and red), and as it is possible to see from the attached figures, there are 6 different colours, maybe more, if you are looking at smallest scale. Merge tool only doesn't allow to get the information of all layers, just the upper one.
    – Krahsin
    Commented Jan 4, 2015 at 22:35
  • create one layer with all the red features and one with all the green features then do your union.
    – Sethinacan
    Commented Jan 5, 2015 at 21:39

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