[QGIS-Developer] QGIS vs GEOS validity check

Tue Jun 7 12:30:12 PDT 2022

[Intranet logo]

Thanks Jeff, I'll ask on the GEOS mailing list for their validity check. However, what about the QGIS specific validity check? Any hint on what is done differently?

Jean-François Bourdon, ing.f.
Analyste en télédétection
Direction des inventaires forestiers
Ministère des Forêts, de la Faune et des Parcs
5700, 4e Avenue Ouest, local A-108
Québec (Québec) G1H 6R1
Téléphone : 418 627-8669, poste 704304
jean-francois.bourdon at mffp.gouv.qc.ca
mffp.gouv.qc.ca

-----Message d'origine-----
De : QGIS-Developer <qgis-developer-bounces at lists.osgeo.org> De la part de Jeff McKenna via QGIS-Developer
Envoyé : 4 juin 2022 06:34
À : qgis-developer at lists.osgeo.org
Objet : Re: [QGIS-Developer] QGIS vs GEOS validity check

Hi JF,

Regarding GEOS, please consider asking for more details through the project's vibrant forum (subscribe at
https://can01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fgeos-devel&data=05%7C01%7Cjean-francois.bourdon%40mffp.gouv.qc.ca%7C334dac66b1924017ad1b08da4615caf3%7C8705e97737814f4790e1c84c8b884da1%7C0%7C0%7C637899356658306764%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=eOB3FPwleIHG1Fx%2BsmdQxEag8PdLpWVp7MEEwV5KG9E%3D&reserved=0 ), I know there was a big release made yesterday and some chatter (project home:
https://can01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flibgeos.org%2F&data=05%7C01%7Cjean-francois.bourdon%40mffp.gouv.qc.ca%7C334dac66b1924017ad1b08da4615caf3%7C8705e97737814f4790e1c84c8b884da1%7C0%7C0%7C637899356658306764%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=sfLgVSdaKdsEHhUaiLgmGi6m0%2BJq6%2FJ2Vev2MtQDXA4%3D&reserved=0 )  GEOS is one of those core libraries, who would greatly appreciate your direct feedback.

PS. hello from the east coast

Thanks,

-jeff

--
Jeff McKenna
GatewayGeo: Developers of MS4W, MapServer Consulting and Training co-founder of FOSS4G
https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgatewaygeo.com%2F&data=05%7C01%7Cjean-francois.bourdon%40mffp.gouv.qc.ca%7C334dac66b1924017ad1b08da4615caf3%7C8705e97737814f4790e1c84c8b884da1%7C0%7C0%7C637899356658306764%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=brYlwYiuoO%2FGu2Du5XWHus%2BnKwyazc4Nrs661jfhEO0%3D&reserved=0

On 2022-06-03 4:25 p.m., Bourdon, Jean-François (DIF) via QGIS-Developer
wrote:
> Intranet logo
>
> Hi Devs,
>
> I had a surprising issue with a specific vector layer and a clip
> operation. Validity check of the geometries seem to be done differently
> if native:clip is used inside a processing script or manually through
> the GUI as a vector layer containing a linestring with duplicate node
> like LINESTRING ((0 0, 1 0, 1 0))  won't cause an issue when the clip is
> done with the GUI but will halt if done inside a processing script (on
> QGIS 3.22.6).
>
> Also, if I run */qgis:checkvalidity/* with the *GEOS* method, no error
> is found, but if I run it with the *QGIS* method, it finds one error
> (/line 1 contains 2 duplicate nodes starting at vertex 2/). So here are
> my questions: what exactly is checked when using the GEOS method and
> what is checked using the QGIS method? Also, do all processing tools
> (qgis: and native: ones) use the same kind of check?
>
> I didn't find anywhere the details of what would be considered an error
> according to the "QGIS spec". Is it documented somewhere or do I need to
> look for hints inside the source code? As for the GEOS method, I only
> found some error examples in the PostGIS documentation and in a FME page
> (https://can01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcommunity.safe.com%2Fs%2Farticle%2Finvalid-ogc-geometry-examples&data=05%7C01%7Cjean-francois.bourdon%40mffp.gouv.qc.ca%7C334dac66b1924017ad1b08da4615caf3%7C8705e97737814f4790e1c84c8b884da1%7C0%7C0%7C637899356658306764%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=iAvp2%2FdNUCBjYFdhKug6dNgJSEYn495pZUPbjv9RUdA%3D&reserved=0
> <https://can01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcommunity.safe.com%2Fs%2Farticle%2Finvalid-ogc-geometry-examples&data=05%7C01%7Cjean-francois.bourdon%40mffp.gouv.qc.ca%7C334dac66b1924017ad1b08da4615caf3%7C8705e97737814f4790e1c84c8b884da1%7C0%7C0%7C637899356658306764%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=iAvp2%2FdNUCBjYFdhKug6dNgJSEYn495pZUPbjv9RUdA%3D&reserved=0>).
> Is there an official documentation of what geometries are invalid
> regarding GEOS?
>
> Thanks a lot for any pointer
>
> *Jean-François Bourdon, ing.f.*
>
> *Analyste en télédétection*
> *Direction des inventaires forestiers*
> *Ministère des Forêts, de la Faune et des Parcs*
> 5700, 4^e Avenue Ouest, local A-108
> Québec (Québec) G1H 6R1
> Téléphone : 418 627-8669, poste 704304
> *_jean-francois.bourdon at mffp.gouv.qc.ca_*
> *mffp.gouv.qc.ca* <http://www.mffp.gouv.qc.ca/accueil.jsp>
>
>

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