I have to create a map with the land register of a place. The data that I already have is unfortunately built out of lines and not polygons. Is there a possibility to create polygons? enter image description here

I already tried the tool “lines to polygons”, but the result is not as good as it should be (sometimes it just summarize a lot of lines to one big square). I also followed that tutorial “Lines to poly QGIS” (https://www.youtube.com/watch?v=bsiSAK3s_jE) but I have no idea how this method should work (I tried it and the result was just one big polygon…).

Is there another good way to do so?

The aim is to get in the end one map with polygons, so that I can “click” on it and get from that polygon the information of its land register number and so on. I use QGIS 2.12.3. -lyon

EDIT: After using the polygonizer tool I got a good result, besides the middle part where a lot of small squares are located. The shapefile has thin lines which are connected through a circle and the polygonizer tool used those circles as polygon and not the whole square. Do I have to do something before with the lines and delete those circles? enter image description here

2 Answers 2


If many of your lines generalize to one big square, this most probably means that their topology is not good (line are not exactly touching, therefore the polygon cannot be delineated).

You could use the GRASS GIS v.clean command in order to snap the lines that are nearly touching. Make sure that you work on a copy because this modify the whole dataset. There is a GRASS plugin to use GRASS from QGIS.

  • when I search for GRASS, I just get a tool called "generalizer". Is it this? And if, which algorithm I should use?
    – user69896
    Commented Apr 15, 2016 at 6:43

Try the polygonize tool vector instead, it can give good results where the lines to polygons tool fails. You can find it by searching the processing toolbox.

enter image description here

  • where exactly can I find that tool? If I go to Processing Toolbox I can choose between geoalgorithms, model and script... is that right so far?
    – user69896
    Commented Apr 15, 2016 at 6:52
  • You can either search in the search bar at the top of the window (where I wrote 'Polygonize' in the screenshot above), or go to QGIS geoalgorithms > Vector geometry tools > Polygonize. Commented Apr 15, 2016 at 7:31
  • I am sorry, but when I write this, there is no result at all... Do I have to install it first or use a different programm but QGIS? I also can't find it as a plugin.. can that be?
    – user69896
    Commented Apr 15, 2016 at 7:47
  • @user69896 - Check in the bottom of the Processing Toolbox that is says "Advanced interface" and not "Simplified interface".
    – Joseph
    Commented Apr 15, 2016 at 8:54
  • ahh great, now I found it! Thanks a lot! It's processing right now, I will let you know about the result :)
    – user69896
    Commented Apr 15, 2016 at 9:27

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