[QGIS-Developer] Split parts tool - invalid output

Andreas Wicht a.wicht at gmail.com
Mon Jun 19 06:54:03 PDT 2017


I would like to raise attention for an issue which was discussed in
length in the qgis-users list [1]

You can ignore the beginning of the discussion where I mixed up "Split
parts" and "Split features".

The split features tool does not produce valid geometries. This can be
easily reproduced by splitting one part of a multipart feature and
then try to split that part again (or save and check the feature with
e.g. postgis' st_isvalid()). This goes hand-in-hand with the comments
in a related, older issue [2].

This makes the workflow much more complex [see 3], if you want to have
a valid output at the end.

The discussion ended in a new Tool in the DigitizingTools (0.11.0)
plugin (thank you Bernhard), which acts much more intuitive from a
users' perspective.
- singlepart features are split and one half inserted as a new feature
- multipart features are split and the user has to choose which part
gets inserted as a new feature, while the other half stays a multipart
feature with all other parts still connected

This raises the question if and how to get that to replace the core tools.

Happy for any input :)


[1] http://osgeo-org.1560.x6.nabble.com/Split-features-tool-behavior-td5321288.html#none
[2] https://issues.qgis.org/issues/12799
[3] http://osgeo-org.1560.x6.nabble.com/Split-features-tool-behavior-tp5321288p5322315.html

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