I seem to have great difficulty using the geoprocessing tools in QGIS. Sometimes they work fine, sometime no matter what I do I get a null result, even though I can see I should be getting a selection. I am mostly using overlap and clip, and I have made sure the two (polygon) shapefiles use the same CRS and that if a selection is used that it overlaps.

I must make it clear that this does seem to be an intermittent problem, but restarts don't cure it.

Is there anything else I should be looking for?

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    Welcome! Please take the tour and see how to ask a good question. It would be best to focus on one of these issues and include what results you are seeing vs what you are expecting as well as more information about the data types you are using. Are you connecting to a database? What type? What errors, if any, do you receive? – MaryBeth Jan 5 '16 at 15:25
  • I am using ESRI shapefiles. The result is simple, two overlapping datasets that share the same CRS are failing to produce any polygons in the resulting shapefile when I use either the clip or intersect tools. – Stub Mandrel Jan 6 '16 at 13:11
  • @StubMandrel - Sometimes the version of QGIS matters (i.e. older versions of QGIS performs geoprocessing operations correctly compared to the latest versions). You could upload your shapefiles to a public server so that others could test your data. – Joseph Jan 12 '16 at 10:18

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