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Tobias,<br>
<br>
Buffer 0 (by the creator of the dataset) is there to prevent that
VALID geometries being written to the shapefile in an INVALID way.<br>
<br>
Buffer 0 on VALID geometries should IMHO never lead to data loss. <br>
<br>
Buffer 0 on INVALID geometries IMHO can lead to good results
depending on the nature of the invalidity. To my experience
repeating points, wrong coordinate ordering and holes touching outer
shells in one point are being repaired well without data loss.<br>
<br>
Please enlighten me with a few links to the tons of tests on the web
showing that buffer 0 is destroying data. My Google skills are not
up to it.<br>
<br>
Regards, Marco<br>
<br>
<div class="moz-cite-prefix">On 29-10-19 10:37, Tobias Wendorff
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:E42C556A-7E3B-4743-8903-C81E4F820612@tu-dortmund.de">
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No! Please NEVER buffer with 0.
<div><br>
</div>
<div>There are tons of tests on the web that proof that this
recommendation of 1980ies GIS experts is destroying data.</div>
<div><br>
</div>
<div>There are modern feature, like „fix geometries“ in GEOS and
others (pprepair).</div>
<div><br>
</div>
<div>We really need the web to forget about this recommendation.<br>
<br>
<div id="AppleMailSignature" dir="ltr">— <br>
<div>Von einem iPhone gesendet und wird daher Fehler
enthalten.</div>
</div>
<div dir="ltr"><br>
Am 29.10.2019 um 10:18 schrieb Marco <<a
href="mailto:deduikertjes@xs4all.nl" moz-do-not-send="true">deduikertjes@xs4all.nl</a>>:<br>
<br>
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<div dir="ltr">
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Hi,<br>
<br>
Validity checks don't check the file format. They check the
validity of the geometries once they are read from the file
into the software.<br>
<br>
The shape file format is a partly documented format. It is
very easy to write a shape file which is not according to
the specs. To my experience ESRI software will do that every
now and again. Very probably you have one of those shape
files.<br>
<br>
You might ask the person who created the files to:<br>
- buffer the geometries with a distance of 0 and the save
the resulting file again.<br>
- and/or export to a different file format (eg geopackage)<br>
<br>
Regards, MArco<br>
<br>
<div class="moz-cite-prefix">On 29-10-19 09:19, Casper
Børgesen wrote:<br>
</div>
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cite="mid:32a3f0fc43bc41908e81ff0af0c7de28@sdfe.dk">
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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Hi
Pepa<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US">I have tried loading and exporting the
multipolygons as WKT using OGR/python and it looks
like the holes are interpreted as polygons.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US">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?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US">My reply doesn’t fix your problem
though, just a few thoughts from me.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US">Regards, Casper<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif"
lang="EN-US">From:</span></b><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif"
lang="EN-US"> gdal-dev <a
class="moz-txt-link-rfc2396E"
href="mailto:gdal-dev-bounces@lists.osgeo.org"
moz-do-not-send="true"><gdal-dev-bounces@lists.osgeo.org></a>
<b>On Behalf Of </b>Pepa Beneš<br>
<b>Sent:</b> 29. oktober 2019 08:10<br>
<b>To:</b> <a class="moz-txt-link-abbreviated"
href="mailto:gdal-dev@lists.osgeo.org"
moz-do-not-send="true">gdal-dev@lists.osgeo.org</a><br>
<b>Subject:</b> [gdal-dev] Fwd: Gdal - multipolygon
- geometry errors instead holes<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<div>
<p class="MsoNormal">HI, <o:p></o:p></p>
</div>
<div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">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. <br>
<br>
Please, write me, how to work with such
geometries in gdal / grass / QGIS / geos world
to see holes too, instead errors?<br>
<br>
In <a
href="https://drive.google.com/file/d/1oRJQVKYDkZji-GLmobov995m9vF00vwf"
moz-do-not-send="true">geometry_problem.zip</a>
there are:<br>
<br>
geometry_problem.qgz .. vizualization in QGIS<br>
<br>
original.shp .. original data prepared in ESRI<br>
original_esri.png .. original.shp seen in
ArcMap (With holes. Author of shp wants have
holes there.)<br>
<br>
original_errors.shp .. geometry errors
prepared by "QGIS Desktop 3.8.3 with GRASS
7.6.1"<br>
original_qgis.png .. original.shp seen in QGIS<br>
<br>
MI/original_to_MI_by_UN.tab .. original.shp
translated from shp to tab by MapInfo -
UniversalTranslator (tried defferent versions
with the same results).<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Thanks <o:p></o:p></p>
</div>
<div>
<div>
<div>
<p class="MsoNormal">Pepa Beneš<o:p></o:p></p>
</div>
</div>
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