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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">and https://gdal.org/programs/gdaltransform.html<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:#1F497D">-Matt</span><i><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></i></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> gdal-dev <gdal-dev-bounces@lists.osgeo.org>
<b>On Behalf Of </b>Simon Eves<br>
<b>Sent:</b> December 10, 2021 12:21 PM<br>
<b>To:</b> Yann-Sebastien Tremblay-Johnston <yanns.tremblay@gmail.com><br>
<b>Cc:</b> gdal dev <gdal-dev@lists.osgeo.org><br>
<b>Subject:</b> Re: [gdal-dev] Transforming Raster Points from GeoTIFF with GCPs<o:p></o:p></span></p>
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<pre><strong><span style="font-family:"Courier New";color:black">*** External email: Do not click on links or attachments except from trusted senders. ***<o:p></o:p></span></strong></pre>
<pre><strong><span style="font-family:"Courier New";color:black">******************************************************************************************</span></strong><span style="color:black"><o:p></o:p></span></pre>
<pre><span style="color:black"><br><br><o:p></o:p></span></pre>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Aha! That's the bit I hadn't found. Thank you! :)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">On Fri, Dec 10, 2021 at 10:38 AM Yann-Sebastien Tremblay-Johnston <<a href="mailto:yanns.tremblay@gmail.com">yanns.tremblay@gmail.com</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Simon,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">See the Transformer API, in particular <a href="https://gdal.org/api/gdal_alg.html?highlight=transformer#_CPPv419GDALTransformerFunc" target="_blank">https://gdal.org/api/gdal_alg.html?highlight=transformer#_CPPv419GDALTransformerFunc</a>
(or gdal.Transformer in Python). <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Sebastien<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">On Fri, Dec 10, 2021 at 10:24 AM Simon Eves <<a href="mailto:simon.eves@omnisci.com" target="_blank">simon.eves@omnisci.com</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">So we have a GeoTiFF of Sentinel-1 imagery which `gdalinfo` reports as having a GCP projection with 210 points, which we'd (perhaps naively?!) like to import directly, transforming
to WGS84 on the fly.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Obviously a simple OGRSpatialReference/OGRCoordinateTransformation transform isn't going to do anything, so I assume we have to do the GCP transform manually.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">I found the GCPCoordinateTransformation class and other supporting code in ogr2ogr_lib.cpp as used by gdaltransform, which seems to do what we need, but of course it's not
in the core GDAL library so we can't "just use it".<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Before embarking on lifting out that code to implement an on-the-fly transformer in our system, I just wanted to make sure I wasn't missing any functionality elsewhere that
would make it easier.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">It may also be more efficient to just kick off a gdalwarp to pre-convert the file so we can just import it with no transformation required, but that seems ugly unless it's
gonna be WAY more efficient?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Thanks,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Simon<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><a href="http://www.omnisci.com/" target="_blank"><span style="text-decoration:none"><img border="0" id="_x0000_i1025" src="http://www2.omnisci.com/l/298412/2018-09-18/3sqpg/298412/61753/OmniSci_Email_Header2.png"></span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#0E4C90">Simon Eves</span></b><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#000001">Senior Graphics Engineer, Rendering Group<br>
100 Montgomery St (5th Floor), San Francisco, CA 94104, USA</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#000001">Email: <a href="mailto:simon.eves@omnisci.com" target="_blank">simon.eves@omnisci.com</a> | Cell: </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#000001">+1 (415) 902-1996</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">_______________________________________________<br>
gdal-dev mailing list<br>
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<a href="https://lists.osgeo.org/mailman/listinfo/gdal-dev" target="_blank">https://lists.osgeo.org/mailman/listinfo/gdal-dev</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><a href="http://www.omnisci.com/" target="_blank"><span style="text-decoration:none"><img border="0" id="_x0000_i1026" src="http://www2.omnisci.com/l/298412/2018-09-18/3sqpg/298412/61753/OmniSci_Email_Header2.png"></span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#0E4C90">Simon Eves</span></b><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#000001">Senior Graphics Engineer, Rendering Group<br>
100 Montgomery St (5th Floor), San Francisco, CA 94104, USA</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#000001">Email: <a href="mailto:simon.eves@omnisci.com" target="_blank">simon.eves@omnisci.com</a> | Cell: </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#000001">+1 (415) 902-1996</span><o:p></o:p></p>
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