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<p class="MsoNormal">Hey Even,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-GB">thank you for the exceptionally quick and helpful reply! Switching to the GPKG/MEMORY drivers did indeed fix the problem, and since I don’t rely on the output being a shapefile this works perfectly fine for me. I never
thought about switching to a different driver.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thanks again for the great work!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">- Luis<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:DE">From:</span></b><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:DE"> Even Rouault <even.rouault@spatialys.com>
<br>
<b>Sent:</b> 20 June 2024 19:43<br>
<b>To:</b> Michaelis, Luis <luis.michaelis@iee.fraunhofer.de>; gdal-dev@lists.osgeo.org<br>
<b>Subject:</b> Re: [gdal-dev] Question: Layer intersection in Python<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p>Luis,<span style="mso-ligatures:none;mso-fareast-language:DE"><o:p></o:p></span></p>
<p>the issue is that shapefile layers do not really support a genuine unknown layer geometry type. They accept it on layer creation, but as soon as you write the first feature into it, the feature layer geometry type is used as the layer geometry type, and
shapefile don't accept a mix of points and multipoints. Which brings to another issue is that
<span lang="EN-GB">PROMOTE_TO_MULTI until now only affected lines and polygons, not points. I've fixed this with
<a href="https://github.com/OSGeo/gdal/pull/10258">https://github.com/OSGeo/gdal/pull/10258</a> .</span><o:p></o:p></p>
<p><span lang="EN-GB">One workaround for you is to write your result in a Memory layer or a GeoPackage layer for example, and then use gdal.VectorTranslate() to convert it to a multipoint shapefile</span><o:p></o:p></p>
<p><span lang="EN-GB">Even</span><o:p></o:p></p>
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<p class="MsoNormal">Le 20/06/2024 à 14:11, Michaelis, Luis via gdal-dev a écrit :<o:p></o:p></p>
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<p class="MsoNormal"><span lang="EN-GB">Hello GDAL devs! </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">I’ve got a question about layer intersection detection.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">I’d like to use the GDAL Python interface to do batched intersection checks between two vector layers, one containing only two-point line strings and one containing terrain contour lines. To compute these intersections,
I would like to use the `ogr.Layer.Intersection` function, since it is supposed do batched intersection detection in native code.
</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">Since all of the intersections will either be points or multi points, I was expecting to use the `KEEP_LOWER_DIMENSION_GEOMETRIES` and `PROMOTE_TO_MULTI` options, to record the intersections into a new layer with a multi-point
geometry. This, however, does not work and I simply don’t get any intersections at all. Setting the geometry to just points does also not work. In neither of these cases are any errors or warnings issued.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">When I use a destination layer with a `wkbUnknown` geometry however, I do get warnings about it trying to add muti-point geometries to a point layer (which I would sort of expect). Setting `SKIP_FAILURES` and saving the
resulting shape, I can actually see the intersection points but as expected, I can’t see the multipoint intersections. They’re simply missing.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">So, the question is: am I missing something? Do need to add some metadata information to the destination layer before computing the intersections or is what I’m trying to do impossible?</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">Here’s the code I’ve written: <a href="https://gist.github.com/lmichaelis-fhg/3ae5ba63b92c1a6ad609baa3ccbfbf80#file-dem-generate-rix-gdal-py-L109-L121">
https://gist.github.com/lmichaelis-fhg/3ae5ba63b92c1a6ad609baa3ccbfbf80#file-dem-generate-rix-gdal-py-L109-L121</a></span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-GB">- Luis</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE"><br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>gdal-dev mailing list<o:p></o:p></pre>
<pre><a href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><o:p></o:p></pre>
<pre><a href="https://lists.osgeo.org/mailman/listinfo/gdal-dev">https://lists.osgeo.org/mailman/listinfo/gdal-dev</a><o:p></o:p></pre>
</blockquote>
<pre>-- <o:p></o:p></pre>
<pre><a href="http://www.spatialys.com">http://www.spatialys.com</a><o:p></o:p></pre>
<pre>My software is free, but my time generally not.<o:p></o:p></pre>
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