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<p class="MsoNormal"><span lang="EN-GB">Hello GDAL devs! <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I’ve got a question about layer intersection detection.<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">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.
<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">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.<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">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.<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">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?<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">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><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"><o:p> </o:p></p>
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