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I have many polygons in a single shapefile and they are overlapping (first figure).

Is there a tool in QGIS to only keep one overlapping area as the one shows in the second figure?

There is a "update" function in ArcGIS but the polygons must be in separate shapefiles.

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PolyGeo
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Bo Wang
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  • I saw the same question posted before but has not yet been solved. https://gis.stackexchange.com/questions/201668/removing-overlapping-part-of-polygons-using-qgis – Bo Wang Jan 01 '21 at 01:09
  • Good question. These polygons are circles created by the "minimum enclosing circle", the results I hope to get are like the circles are eaten by nearby ones. – Bo Wang Jan 01 '21 at 03:00
  • What is the "minimum enclosing circle"? What should the input look like for the polygons in your first picture? Is it always the earlier drawn polygon that gets updated? – PolyGeo Jan 01 '21 at 03:02
  • This algorithm calculates the minimum enclosing circle which covers each feature in an input layer (river centerline in my case). You can find it in the QGIS processing toolbox. – Bo Wang Jan 01 '21 at 03:24
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    Does this answer your question? Removing overlapping part of polygons using QGIS? – Ahsan Mukhtar Jan 01 '21 at 04:11
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    If you have ArcGIS and an advanced license you can use feature to polygon https://resources.arcgis.com/en/help/main/10.2/index.html#//00170000003n000000 to planarize your polygons (no overlaps) however the overlap area does not belong to any of the source polygons you will need to find a hierarchy to merge the planar polygons by, if you don't have a preference a tool like Eliminate https://resources.arcgis.com/en/help/main/10.2/index.html#//00170000005p000000 will dissolve overlaps into the adjacent features based on longest side or largest overlap area. – Michael Stimson Jan 01 '21 at 05:20
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    If you don't have ArcGIS and an advanced license have a look at https://gis.stackexchange.com/questions/303430/removing-overlapping-polygon-boundaries-within-same-layer-in-qgis and see if that suits your purpose. – Michael Stimson Jan 01 '21 at 05:20

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The methods mentioned by @Michael Stimson work very well. I tried both ArcGIS and QGIS. The "feature to polygon" in ArcGIS and "Polygon self-intersection" in QGIS do the same thing. They "return a new layer with sub-divided polygons (while only one of the duplicated overlapping area is retained)". The only difference is that in ArcGIS, the new vector lost the original attribute (e.g. segment ID) while it is preserved in QGIS. Therefore, QGIS is better at doing this. Detailed methods are described here by Kazuhito.

  1. SAGA | Vector polygon tools - Polygon self-intersection tool. This tool returns a new layer with sub-divided polygons (while only one of the duplicated overlapping area is retained).
  2. Vector selection - Select by expression tool. Use an expression to select the sliver polygons (see below example).
  3. List item Vector geometry - Eliminate selected polygons tool will remove these selected features. (I would suggest the Largest common boundary option... it will give more naturally-looking output.)

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Bo Wang
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