[Qgis-user] Fix Geometries

[Tobias Wendorff]

Just do it the hard/smart way.

Google for some test suits with invalid geometries, run them in QGIS with the different methods and write a summary.

Or so it the fun(ny) way and create your own invalid geodata. Self-intersecting, overlapping etc.

— 
Von einem iPhone gesendet und wird daher Fehler enthalten.

> Am 22.05.2019 um 12:08 schrieb DelazJ <delazj at gmail.com>:
> 
> Hi Jürgen,
> 
> I know that we don't have black box and this was certainly not the appropriate term to use. Sorry. Still, most of the users have no means to read the code but need to use any of these options. Without understanding what they do, it becomes simply a click-click business (not empowering them). So it could be nice we shed some light on them (maybe something for a grant proposal?).
> 
> Greetings,
> Harrissou
> 
>> Le mer. 22 mai 2019 à 11:55, Jürgen E. Fischer <jef at norbit.de> a écrit :
>> Hi Harrissou,
>> 
>> On Wed, 22. May 2019 at 11:03:56 +0200, DelazJ wrote:
>> > *> 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).
>> 
>> We don't have a blackbox.  The ultimate source of information about the QGIS
>> method is the QGIS method:
>> 
>> https://github.com/qgis/QGIS/blob/master/src/core/qgsgeometryvalidator.cpp
>> 
>> But there isn't a comparison on what GEOS and that method do differently.
>> 
>> 
>> Jürgen
>> 
>> -- 
>> Jürgen E. Fischer           norBIT GmbH             Tel. +49-4931-918175-31
>> Dipl.-Inf. (FH)             Rheinstraße 13          Fax. +49-4931-918175-50
>> Software Engineer           D-26506 Norden            https://www.norbit.de
>> QGIS release manager (PSC)  Germany                    IRC: jef on FreeNode
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