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<div class="moz-cite-prefix">Le 16/01/2024 à 11:59, andy via
QGIS-User a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CAHEdGZMfzdKpArRj6zL6Js-nEzz1tzZprTq-GdhTQr=EdEHyQg@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Hi,
<div>I'm doing NTv2-transformation, using this gsb file:</div>
<div><a
href="https://web.archive.org/web/20201018143532/https://provincia.agrigento.sitr.it/scaricabili/NTv2/ItalyED50toWGS84_NTV2_GN.gsb"
moz-do-not-send="true" class="moz-txt-link-freetext">https://web.archive.org/web/20201018143532/https://provincia.agrigento.sitr.it/scaricabili/NTv2/ItalyED50toWGS84_NTV2_GN.gsb</a></div>
<div><br>
</div>
<div>I have copied it in "C:\OSGeo4W\share\proj" and I have
defined this custom projection:</div>
<div>+proj=utm +zone=33 +ellps=intl
+nadgrids=ItalyED50toWGS84_NTV2_GN.gsb +units=m +no_defs
+type=crs<br>
</div>
<div><br>
</div>
<div>If I test it in QGIS, in the custom CRS window, using
lon=13 and lat=38, I have in output:</div>
<div>324388.7743<br>
</div>
<div>4207772.1972<br>
</div>
</div>
</blockquote>
<p>Did you try with the full path +nadgrids=C:\OSGeo4W\share\proj\ItalyED50toWGS84_NTV2_GN.gsb ?</p>
<p>If I do that (well on Linux: "+proj=utm +zone=33 +ellps=intl +nadgrids=/home/even/qgis/qgis/build_ubuntu2204/ItalyED50toWGS84_NTV2_GN.gsb +units=m +no_defs"), I do get the correct result 324454.6136 4207894.9261 in QGIS (master)</p>
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<p>
</p>
<p>But, what is the history of this "ghost" grid that requires fetching it from web.archive.org ? Has it had some official status, and could it be provided under an open data license ? If so, it would be great if Italian authorities could register to IOGP/EPSG this grid for ED50 -> WGS 84 for Italy... Then we could ship it in PROJ-data.</p>
<p>But I remember complicated discussion at FOSS4G Firenze with the guys from the geodetic authority (<a class="moz-txt-link-freetext" href="https://www.igmi.org">https://www.igmi.org</a>).... Not sure if that has lead to anywhere.</p>
<p>Even
</p>
<span style="white-space: pre-wrap">
</span>
<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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