I created polygons from a raster on which I ran an edge detection filter. I turned the edges into a polygon layer (multipart splitted into single parts). The intention was to have circular polygons at the end, but now there many single polygons forming one circle but are not touching each other, so I cannot connect these. The single yellow polygon in the figure below is an example.

Can anybody tell me how to connect all polygons in order to form a circle? The polygon is available as a download here. I work in SAGA, GRASS, or QGIS, or in R.

enter image description here

  • Dear Cyril - no worries. Problem solved. – Jens Jan 23 '19 at 8:48
  • Good, I'm happy for you... – Cyril Mikhalchenko Jan 23 '19 at 10:36

Polygons are touching at a point.

Do a little Buffer, Dissolve, and Multipart to singleparts again.

There is no way to preserve exactly those geometries and to be merged.

If you wanted, you can then make a negative Buffer to return them to their original size, with Round type of End Cap Style, so they do not touch each other again.

| improve this answer | |
  • Perfect! Worked very well. I simply added a small buffer (distance = 0.01). Dissolve was then done while performing the buffering. Many thanks! – Jens Jan 23 '19 at 8:47
  • @Jens, most welcome! – Gabriel De Luca Jan 23 '19 at 10:22

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