Bug report #18201

Dissolve creates wrong output

Added by Erik Sigra over 2 years ago. Updated over 2 years ago.

Status:Closed
Priority:Normal
Assignee:Victor Olaya
Category:Processing/QGIS
Affected QGIS version:2.18.16 Regression?:No
Operating System:Gentoo Easy fix?:No
Pull Request or Patch supplied:No Resolution:invalid
Crashes QGIS or corrupts data:No Copied to github as #:26092

Description

The attached screenshot shows polygons coloured by Id. On top of them are red dotted lines showing the borders of other polygons created by the Dissolve command.

The red dotted lines seem to mostly be in the right places, but near the bottom right corner is an erroneous line. It seems like two of the polygons created by Dissolve overlap.

dissolve_issue.png - screenshot (320 KB) Erik Sigra, 2018-02-24 12:53 AM

dissolve_issue.qgs - project (24 KB) Erik Sigra, 2018-02-24 12:54 AM

test-polygons.dbf - data (1.39 KB) Erik Sigra, 2018-02-24 12:54 AM

test-polygons.prj - data (377 Bytes) Erik Sigra, 2018-02-24 12:54 AM

test-polygons.qpj - data (568 Bytes) Erik Sigra, 2018-02-24 12:54 AM

test-polygons.shp - data (18.5 KB) Erik Sigra, 2018-02-24 12:54 AM

test-polygons.shx - data (1.06 KB) Erik Sigra, 2018-02-24 12:54 AM

voronoi_issue.png - screenshot (355 KB) Erik Sigra, 2018-02-24 02:38 AM

test-voronoi.dbf - data (1.39 KB) Erik Sigra, 2018-02-24 02:38 AM

test-voronoi.qpj - data (568 Bytes) Erik Sigra, 2018-02-24 02:38 AM

test-voronoi.prj - data (377 Bytes) Erik Sigra, 2018-02-24 02:38 AM

test-voronoi.shx - data (1.06 KB) Erik Sigra, 2018-02-24 02:38 AM

test-voronoi.shp - data (3.46 KB) Erik Sigra, 2018-02-24 02:38 AM

voronoi_issue.qgs - project (26.3 KB) Erik Sigra, 2018-02-24 02:38 AM

History

#1 Updated by Erik Sigra over 2 years ago

  • Assignee changed from Victor Olaya to Erik Sigra
  • Status changed from Open to Closed

Sorry, seems like I had a bad GIS day. There is overlap in the input to dissolve.

#2 Updated by Erik Sigra over 2 years ago

There might be a bug in QGIS after all. But in Voronoi. It seems to create overlapping polygons. The attached screenshot shows the points used as input to Voronoi and the generated polygons with half transparency so that overlap can be seen.

#3 Updated by Giovanni Manghi over 2 years ago

  • Status changed from Reopened to Closed
  • Resolution set to invalid

Erik Sigra wrote:

There might be a bug in QGIS after all. But in Voronoi. It seems to create overlapping polygons. The attached screenshot shows the points used as input to Voronoi and the generated polygons with half transparency so that overlap can be seen.

confirmed, but this is a different issue and you need to file a separate ticket.

#4 Updated by Erik Sigra over 2 years ago

#5 Updated by Alexander Bruy over 2 years ago

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