In QGIS after creating contour lines by extracting them from a DEM (Extraction > Contour) and smoothing them (Line Smoothing) I noticed this situation:

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In order to smooth out the corners displayed in the screen more, I set the parameters of the tool in this way:

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The result is this:

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Every line is broken. Is there an easy way to join them without having to modify them one by one and without losing the data for all of them?

  • That looks like a bug to me, please report it at github.com/qgis/qgis/issues – bugmenot123 Nov 6 '20 at 7:34
  • 2
    Not an answer, but I always follow the creation of contours in gdal from LiDAR by using the v.generalize tool but primary goal is to reduce the number of vertices hence file size instead of smoothing. For true smoothing you might instead consider making a "smoothed" DEM (e.g. Focal statistics or r.neighbors in GRASS) and then make the contours from it. – johns Nov 6 '20 at 14:14

From the Processing toolbox you can tryv.cleantool from GRASS. Make sure you use the snap option and that the snapping distance is adequate. However note that this tool afects the placement of your line but since you already went to several simplification steps this should an acceptable trade off for you.

  • I'm afraid it's not working. I've tried to adjust the parameters several times but the situation remains unchanged. – ddomizia Feb 8 '20 at 15:25

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