Bug report #14292

'Merge Selected Features' does not remove unnecessary nodes

Added by Paul Kanelli almost 4 years ago. Updated almost 4 years ago.

Status:Closed
Priority:Normal
Assignee:-
Category:Digitising
Affected QGIS version:master Regression?:No
Operating System: Easy fix?:No
Pull Request or Patch supplied:No Resolution:wontfix
Crashes QGIS or corrupts data:No Copied to github as #:22283

Description

1.) add a new polygon feature
2.) use 'Split Features' tool to split the feature
3.) use 'Merge Selected Features' tool to merge the features

Now there are new nodes where the features were merged. This may cause trouble processing geometries:

http://gis.stackexchange.com/questions/180593/unexpected-behaviour-using-st-equals-with-qgis

History

#1 Updated by Nyall Dawson almost 4 years ago

  • Resolution set to wontfix
  • Status changed from Open to Closed

I don't think this is a bug... It's not safe to auto remove these, as floating point inaccuracies will slightly alter the geometry when the split operation is performed. Use the hausdorff distance instead as a "fuzzy" comparison (http://postgis.net/docs/ST_HausdorffDistance.html), or run a simplify on the resultant geometry with a very small tolerance to try and remove these extra vertices.

#2 Updated by Paul Kanelli almost 4 years ago

Thanks for your detailed explanation!

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