[gdal-dev] Fwd: Gdal - multipolygon - geometry errors instead holes

[Casper Børgesen]

Hi Pepa

I have tried loading and exporting the multipolygons as WKT using OGR/python and it looks like the holes are interpreted as polygons.

FME displays the data (correctly?) with holes and its validation engine doesn’t find any errors. BUT a year ago I sent a bug report to SAFE because FME did some automatic geometry repair when loading data => the various programs could be fixing issues automatic which means you won’t see them. Not to imply that ESRI does automatic geometry repair in the background, but which program can you definitely trust to correctly represent the contents of your data set?

I tend to trust GDAL/OGR (which means I also trust QGIS) because its open source and the developers are normally pretty good at reporting back how the software treats data.

My reply doesn’t fix your problem though, just a few thoughts from me.

Regards, Casper

From: gdal-dev <gdal-dev-bounces at lists.osgeo.org> On Behalf Of Pepa Beneš
Sent: 29. oktober 2019 08:10
To: gdal-dev at lists.osgeo.org
Subject: [gdal-dev] Fwd: Gdal - multipolygon - geometry errors instead holes

HI,

I recieved one shapefile. Gdal / Grass / QGIS finds two geometry errors in it. Other GIS SW (ArcMap, MapInfo (via Universal translator or opening shp natively)) theay can't see this geometries as errors. Instead errors they can see regular multipolygons with holes there. Author of this shp wants to see holes there too = in his opinion there are correct data only.

Please, write me, how to work with such geometries in gdal / grass / QGIS / geos world to see holes too, instead errors?

In geometry_problem.zip<https://drive.google.com/file/d/1oRJQVKYDkZji-GLmobov995m9vF00vwf> there are:

geometry_problem.qgz .. vizualization in QGIS

original.shp .. original data prepared in ESRI
original_esri.png .. original.shp seen in ArcMap (With holes. Author of shp wants have holes there.)

original_errors.shp .. geometry errors prepared by "QGIS Desktop 3.8.3 with GRASS 7.6.1"
original_qgis.png .. original.shp seen in QGIS

MI/original_to_MI_by_UN.tab .. original.shp translated from shp to tab by MapInfo - UniversalTranslator (tried defferent versions with the same results).

Thanks
Pepa Beneš
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