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<p>Jukka,<br>
</p>
<div class="moz-cite-prefix">Le 22/03/2022 à 12:56, Rahkonen Jukka
(MML) a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:5834688c94fa4f32a773c3e91798323f@maanmittauslaitos.fi">
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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">See this question <a
href="https://gis.stackexchange.com/questions/426418/create-rectified-geotiff-given-aux-xml-produced-from-arcgis"
moz-do-not-send="true" class="moz-txt-link-freetext">
https://gis.stackexchange.com/questions/426418/create-rectified-geotiff-given-aux-xml-produced-from-arcgis</a>?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The GeoTIFF driver
documentation <a
href="https://gdal.org/drivers/raster/gtiff.html#georeferencing"
moz-do-not-send="true" class="moz-txt-link-freetext">
https://gdal.org/drivers/raster/gtiff.html#georeferencing</a>
says about the order in which the georeferencing is searched
“By default, information is fetched in following order
(first listed is the most prioritary): PAM (Persistent
Auxiliary metadata) .aux.xml sidecar file, INTERNAL (GeoTIFF
keys and tags), TABFILE (.tab), WORLDFILE (.tfw,
.tifw/.tiffw or .wld).”<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">However, in this case it
seems that GeoTIFF tags are used instead of PAM if not
especially asked with --config GDAL_GEOREF_SOURCES PAM</span></p>
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</blockquote>
<p>Yes I can see in the code that for that particular case with
standard TIFF tags expressing a geotransform (which is completely
buggy on the sample file of the stackexchange thread) an this ESRI
GeodataXform .aux.xml stuff, both will be reported. I've just
fixed this in
<a class="moz-txt-link-freetext" href="https://github.com/OSGeo/gdal/commit/acbd907896418330315f3e6febf620d4686023ac">https://github.com/OSGeo/gdal/commit/acbd907896418330315f3e6febf620d4686023ac</a><br>
</p>
<p>Adding -to SRC_METHOD=GCP_POLYNOMIAL or GCP_TPS to gdalwarp will
force the GCPs to be used.</p>
<blockquote type="cite"
cite="mid:5834688c94fa4f32a773c3e91798323f@maanmittauslaitos.fi">
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<p class="MsoNormal"><span lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I am also curious to
know how the SourceGCP values in this PAM file gets
converted into pixel rows and columns. For example these
values<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><SourceGCPs
xsi:type="typens:ArrayOfDouble"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
<Double>3.3670799903498199</Double><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">
<Double>14.344873843184562</Double><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">seem to turn into
(1010.12399710495,3376.53784704463). How does it happen and
where is it documented? I think there must happen some
scaling and offsetting but is this something ESRI specific?
I found this ESRI document but there the columns and rows
appear unscaled in the aux.xml file <a
href="https://doc.arcgis.com/en/imagery/workflows/browse-imagery/workflow/workflow-appendices.htm"
moz-do-not-send="true" class="moz-txt-link-freetext">
https://doc.arcgis.com/en/imagery/workflows/browse-imagery/workflow/workflow-appendices.htm</a>.</span></p>
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<p>I see support for the ESRI GeodataXform .aux.xml stuff was added
in <a class="moz-txt-link-freetext" href="https://github.com/OSGeo/gdal/commit/7025e356c28">https://github.com/OSGeo/gdal/commit/7025e356c28</a></p>
<p>The interesting part to explain the difference between the values
in the files and the ones reported by gdalinfo is in:<br>
</p>
<p>+ // The origin used is the bottom left
corner, <br>
+ // and raw values are in inches !<br>
+ pasGCPList[i].dfGCPPixel =
adfSourceGCPs[2*i] *<br>
+
CPLAtof(pszTIFFTagXRes);<br>
+ pasGCPList[i].dfGCPLine = nRasterYSize -<br>
+ adfSourceGCPs[2*i+1] *
CPLAtof(pszTIFFTagYRes);<br>
<br>
</p>
<p>At least this was found to be necessary on the sample file that
was used to develop this code. And actually trying with the file
in the stackexchange thread, this leads to correct georeferencing.<br>
</p>
<p>Even<br>
</p>
<blockquote type="cite"
cite="mid:5834688c94fa4f32a773c3e91798323f@maanmittauslaitos.fi">
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<p class="MsoNormal"><span lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-Jukka Rahkonen-<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<br>
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</blockquote>
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