[Qgis-user] Fix Geometries

[DelazJ]

Hi,
Andreas, this is a question that I regularly see and let me quote an early
reply of Jürgen Fischer (on qgis-user list, 2017/04/27 in a discussion
entitled "Difference between QGIS and GEOS method?" - I fail to find the
discussion in the archives):





*> The QGIS method is an internal method that can return multiple errors
and was > IIRC introduced, when GEOS could just report one error at a time
without a > location and we couldn't or didn't yet use it threaded.
Essentially it was > just made to highlight digitizing errors.  It might
miss some rules or > interpret some edge cases differently than GEOS.*

So there are some historical reasons. Unfortunately, this does not seem
enough to clarify things and wouldn't deserve a place in the docs (I may be
wrong!).  If anyone has more details, please tell us. I think it could be
worth clarify and document the differences if they are clear enough or
merge the tools in the future if possible, avoiding confusion for users (we
should not have kind of black box ;) in QGIS).

Regards,
Harrissou


Le mer. 22 mai 2019 à 09:53, Andreas Wicht <a.wicht at gmail.com> a écrit :

> Hi,
>
> > The most predictable tool is the vector/geometry tools/Check validity
> > using the 'QGIS' Method (not GEOS).
>
> Is there actually a documentation/information on the difference of
> validation here or why one would want to use 'QGIS' instead of 'GEOS'
> for validation?
>
> https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/qgis/vectorgeometry.html#check-validity
> does not provide much information on that.
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