Tolerance (snapping) during analyses

[qgib]

Author Name: Paolo Cavallini (@pcav)
Original Redmine Issue: 9326

Redmine category:processing/qgis

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In case of layers with essentially the same shapes, with different precision, the diff between these layers produces a number of virtually 0 width polygons.
These microareas are tricky and time consuming to remove (if they are isolated, a possible solution is to select and remove those smaller than an arbitrary threshold, but if they are linked to some "real" polygons, this will not work).

I suggest to add a parameter in analyses, to either snap original data within a threshold before running the analysis, or to clean up the results afterwards

[qgib]

Author Name: Paolo Cavallini (@pcav)

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See a discussion on: http://lists.osgeo.org/pipermail/qgis-developer/2014-January/030119.html

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Probably this could be solved with a new command, allowing the user to arbitrarily reduce the precision of coordinates (filling up the rest with 0s).

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• category_id was changed from 44 to Processing/QGIS

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Still valid? With automatic reprojection now in Processing the issue can be even more serious.

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• status_id was changed from Open to Feedback
• description was changed from In case of layers with essentially the same shapes, with different precision, the diff between these layers produces a number of virtually 0 width polygons.
  These microareas are tricky and time consuming to remove (if they are isolated, a possible solution is to select and remove those smaller than an arbitrary threshold, but if they are linked to some "real" polygons, this will not work).

I suggest to add a parameter in analyses, to either snap original data within a threshold before running the analysis, or to clean up the results afterwards to In case of layers with essentially the same shapes, with different precision, the diff between these layers produces a number of virtually 0 width polygons.
These microareas are tricky and time consuming to remove (if they are isolated, a possible solution is to select and remove those smaller than an arbitrary threshold, but if they are linked to some "real" polygons, this will not work).

I suggest to add a parameter in analyses, to either snap original data within a threshold before running the analysis, or to clean up the results afterwards

[alexbruy]

Probably we can close this, as Processing now offers several tool for snapping which can be used before doing analysis.

[pcav]

Agreed, thanks