Bug report #1758

Tools (Ftools): clip and difference tools give the same results

Added by Giovanni Manghi about 10 years ago. Updated almost 10 years ago.

Status:Closed
Priority:Low
Assignee:cfarmer -
Category:Python plugins
Affected QGIS version: Regression?:No
Operating System:All Easy fix?:No
Pull Request or Patch supplied: Resolution:worksforme
Crashes QGIS or corrupts data: Copied to github as #:11818

Description

a) pick a layer

b) pick a grid that overlaps the above layer

c) do a "clip" operation with ftools using the grid as "clip layer"

d) do a "intersect" operation with ftools using the grid as "clip layer"

e) compare the results, seems to me identical

Should the "Clip Tool "use just the borders of the "clip layer"?.

Here you can download the shapesfiles (epsg 20790) I used/resulted in my test (qgis 1.2 rev. 11023, Ubuntu 9.04). "Inso" is the base layer, the rest are pretty self-explanatory.

http://www.faunalia.pt/downloads/ftools_test.tar.gz

Screenshot-1.png (4.79 KB) Giovanni Manghi, 2009-08-11 01:33 AM

Associated revisions

Revision 52996e72
Added by cfarmer - about 10 years ago

Fix clip geoprocessing function: Fixes #1758

git-svn-id: http://svn.osgeo.org/qgis/trunk/[email protected] c8812cc2-4d05-0410-92ff-de0c093fc19c

Revision b466b2b6
Added by cfarmer - about 10 years ago

Fix clip geoprocessing function: Fixes #1758

git-svn-id: http://svn.osgeo.org/qgis/[email protected] c8812cc2-4d05-0410-92ff-de0c093fc19c

Revision ed40da8f
Added by cfarmer - about 10 years ago

Additional updates to 'Clip' Geoprocessing tool: Properly fixes #1758.

git-svn-id: http://svn.osgeo.org/qgis/trunk/[email protected] c8812cc2-4d05-0410-92ff-de0c093fc19c

Revision ad3028bb
Added by cfarmer - about 10 years ago

Additional updates to 'Clip' Geoprocessing tool: Properly fixes #1758.

git-svn-id: http://svn.osgeo.org/qgis/[email protected] c8812cc2-4d05-0410-92ff-de0c093fc19c

History

#1 Updated by cfarmer - about 10 years ago

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

Should now be fixed in b466b2b6 (SVN r11340). Please test and reopen ticket if not fixed properly.
Note: In some cases geometries may still be mis-formed. This is a separate issue, and will be addressed soon.

- Carson

#2 Updated by Giovanni Manghi about 10 years ago

Replying to [comment:2 cfarmer]:

Note: In some cases geometries may still be mis-formed. This is a separate issue, and > will be addressed soon.

See attached image. Is this one of this cases?

#3 Updated by cfarmer - about 10 years ago

Replying to [comment:4 lutra]:

See attached image. Is this one of this cases?

Yes. This appears to be an issue with the type of geometries that GEOS is returning. I have tried to eliminate these spurious geometries, but as you can see there is still some cleaning up to do...

-Carson

#4 Updated by Giovanni Manghi about 10 years ago

I don't know if it is important, but have you noticed that with Intersect this doesn't happens?

#5 Updated by cfarmer - about 10 years ago

Replying to [comment:4 lutra]:

See attached image. Is this one of this cases?

This should now be behaving properly in ad3028bb (SVN r11349). I have changed the underlying logic, so this tools should be slightly faster, and work better with large, complex datasets.

The test dataset provided with this ticket now works properly (as far as I can tell), however, please test and reopen this ticket if problem(s) persists.

-Carson

#6 Updated by Giovanni Manghi about 10 years ago

Replying to [comment:7 cfarmer]:

The test dataset provided with this ticket now works properly (as far as I can tell), however, please test and reopen this ticket if problem(s) persists.

Seems to work fine!

Thanks a lot,

-- Giovanni --

#7 Updated by Paolo Cavallini almost 10 years ago

  • Status changed from Closed to Feedback
  • Resolution deleted (fixed)

Now clip and difference seem to give the same result

#8 Updated by Giovanni Manghi almost 10 years ago

  • Resolution set to worksforme
  • Status changed from Feedback to Closed

Hi Paolo, I made a few tests and seems to me that clip and difference are giving the right results. Feel free to reopen if is the case.

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