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I am an absolute beginner in GIS software.

My goal is to get a list (or something similar) of all the empty polygons/areas between the colored ones. It would be perfect if the size and location of the polygons would be visible too.

My current work:

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    Are these "blank space" actually polygon ? how did you get the colored polygon ?
    – J.R
    Commented Mar 4, 2022 at 14:06
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    Create a dummy polygon covering the whole area, use difference to substract the coloured areas, tada.
    – Erik
    Commented Mar 4, 2022 at 14:15
  • @J.R it's actually blank space! The colored areas are WFS Layers.
    – Mabignix
    Commented Mar 7, 2022 at 10:51

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I guess that you've got different polygon layers for the colored areas and another polygon layer with the provinces.

What I would do, first is to filter the provinces layer (right click > filter),

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selecting the one that you want to work with (double click on the field with the provinces names; equal sign; All button; double click on the selected province).

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After that, combine all "coloured" layers using vectorial > Data Management Tools > Combine vector layers

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Select all layers and run the algorithm and you'll get a new combined layer. Now, execute the Difference tool vectorial > Geoprocess > Difference with the provinces layer as the imput layer and the new combined layer as the overlay layer.

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You'll get a new layer with the "uncoloured" polygons. After that, you can create a new field for that new layer, using the field calculator

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with the following settings

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You'll get the area of each polygon in the units of the layer.

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  • Hey @jpinilla, first of all: Many thanks for your effort, I appreciate it very much. So the problem is that the purple lines define the area where I want to do the "difference" Process. I googled a lot on how to convert the purple Raster file into a useable shape file, so I can remove the colored polygons from it, but it always throws an Error. Do you know a solution? I think the error occurs because the Raster is also an WFS import...
    – Mabignix
    Commented Mar 7, 2022 at 12:21
  • Moreover I tried to create my own polygon in the shape of the purple raster layer. After I created the combined vector layer of the colored polygons, I did the "difference" process with my self-created polygon and the new combined one. It throwed an error because the geometry of some objects aren't fitting. I went to the properties and enabled "Ignore features with invalid geometries" but I would like to do the process without any ignoring of bugs. Is that somehow possible? Maybe with converting the combined file into one shape file with only one "layer" in it?
    – Mabignix
    Commented Mar 7, 2022 at 13:13
  • What I would do is try to obtain the provinces limits in a vector format, since converting raster to vector is quite often a bad idea. Administrative boundaries are usually available through official sites, regional or national. After that, run the "correct invalid geometries" algorithm for the vector layers you're working with before any other operation.
    – jpinilla
    Commented Mar 7, 2022 at 13:29
  • Perfect. I will try that. Thanks a lot!
    – Mabignix
    Commented Mar 8, 2022 at 11:55
  • I found provinces limits in vector format and it worked just fine. Thanks a lot!
    – Mabignix
    Commented Apr 2, 2022 at 10:16

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