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<p>Michael,</p>
<p>it is well possible this might have worked in the past due to
slightly different behavior of GDAL and/or PROJ, but the current
behavior seems consistent to me. You're trying to transform
between 2 compound CRS, the source one with a unknown vertical
datum and the target one with EGM2008 height. There's nothing
reasonable that PROJ can do regarding the vertical transformation
in that situation, in particular it would be quite a bold
assumption to assume that the source CRS is actually meant to be
refering to ellipsoidal heights. If you override with -s_srs
EPSG:32617 (or drop REPORT_COMPD_CS=TRUE), then GDAL will
auto-promote the source CRS to a 3D CRS with ellipsoidal heights,
which could also be questionable from a purist point of view, but
is the behaviour we have had for long now.</p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 12/04/2023 à 10:36, Michael Smith a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:AADE155E-B951-4290-9DA1-CE5C41CF37F9@gmail.com">
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<p class="MsoNormal">I have a file with a projection shown,
using REPORT_COMPD_CS=TRUE of:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">COMPOUNDCRS["WGS 84 / UTM zone 17N +
unknown",<o:p></o:p></p>
<p class="MsoNormal"> PROJCRS["WGS 84 / UTM zone 17N",<o:p></o:p></p>
<p class="MsoNormal"> BASEGEOGCRS["WGS 84",<o:p></o:p></p>
<p class="MsoNormal"> DATUM["World Geodetic System
1984",<o:p></o:p></p>
<p class="MsoNormal"> ELLIPSOID["WGS
84",6378137,298.257223563,<o:p></o:p></p>
<p class="MsoNormal">
LENGTHUNIT["metre",1]]],<o:p></o:p></p>
<p class="MsoNormal"> PRIMEM["Greenwich",0,<o:p></o:p></p>
<p class="MsoNormal">
ANGLEUNIT["degree",0.0174532925199433]],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",4326]],<o:p></o:p></p>
<p class="MsoNormal"> CONVERSION["UTM zone 17N",<o:p></o:p></p>
<p class="MsoNormal"> METHOD["Transverse Mercator",<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",9807]],<o:p></o:p></p>
<p class="MsoNormal"> PARAMETER["Latitude of natural
origin",0,<o:p></o:p></p>
<p class="MsoNormal">
ANGLEUNIT["degree",0.0174532925199433],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",8801]],<o:p></o:p></p>
<p class="MsoNormal"> PARAMETER["Longitude of natural
origin",-81,<o:p></o:p></p>
<p class="MsoNormal">
ANGLEUNIT["degree",0.0174532925199433],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",8802]],<o:p></o:p></p>
<p class="MsoNormal"> PARAMETER["Scale factor at
natural origin",0.9996,<o:p></o:p></p>
<p class="MsoNormal"> SCALEUNIT["unity",1],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",8805]],<o:p></o:p></p>
<p class="MsoNormal"> PARAMETER["False
easting",500000,<o:p></o:p></p>
<p class="MsoNormal"> LENGTHUNIT["metre",1],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",8806]],<o:p></o:p></p>
<p class="MsoNormal"> PARAMETER["False northing",0,<o:p></o:p></p>
<p class="MsoNormal"> LENGTHUNIT["metre",1],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",8807]]],<o:p></o:p></p>
<p class="MsoNormal"> CS[Cartesian,2],<o:p></o:p></p>
<p class="MsoNormal"> AXIS["easting",east,<o:p></o:p></p>
<p class="MsoNormal"> ORDER[1],<o:p></o:p></p>
<p class="MsoNormal"> LENGTHUNIT["metre",1]],<o:p></o:p></p>
<p class="MsoNormal"> AXIS["northing",north,<o:p></o:p></p>
<p class="MsoNormal"> ORDER[2],<o:p></o:p></p>
<p class="MsoNormal"> LENGTHUNIT["metre",1]],<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",32617]],<o:p></o:p></p>
<p class="MsoNormal"> VERTCRS["unknown",<o:p></o:p></p>
<p class="MsoNormal"> VDATUM["unknown"],<o:p></o:p></p>
<p class="MsoNormal"> CS[vertical,1],<o:p></o:p></p>
<p class="MsoNormal"> AXIS["up",up,<o:p></o:p></p>
<p class="MsoNormal"> LENGTHUNIT["metre",1,<o:p></o:p></p>
<p class="MsoNormal"> ID["EPSG",9001]]]]]<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">When trying to gdalwarp to EGM2008 using
gdalwarp -t_srs epsg:32617+3855, vertical datum reprojection
does not occur unless I overwride the source srs with -s_srs
epsg:32617. Using GDAL 3.6.2 and proj 9.1.1. With proj_debug,
I can see that the PROJ_TRACE: vgridshift: is not occurring
unless the srs is overridden. I’m fairly sure that this has
worked in the past but I can’t say exactly which version. This
is an older geotiff that was written about 7 years ago. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal">-- <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Michael Smith<o:p></o:p></p>
<p class="MsoNormal">US Army Corps / Remote Sensing GIS
Center<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<br>
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</blockquote>
<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.spatialys.com">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
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