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<p>Javier,</p>
<p>I believe that registering a concatenated operation for ITRF2020
-> ETRS89 = ITF2020->ETRF2020+ETRF2020->ETRS89 in the
database should be enough for PROJ to infer the ITRF2020 ->
CH1903+ pipeline</p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 27/08/2024 à 19:29, Javier Jimenez
Shaw via PROJ a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CADRrdKuP1wWPOT4a_TUduBNM_0Hfgp0qfhEp1aadpECng8hyCg@mail.gmail.com">
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<div>Hi</div>
<div><br>
</div>
<div>I am now facing transformations with ITRF2020 with
time(yes, because Skylark, but I guess more NTRIPs are going
to do (or already doing) the same)</div>
<div><br>
</div>
<div>The point is when the destination CRS does not have a
direct transformation from ITRF2020 (or almost).</div>
<div><br>
</div>
<div>For instance, EPSG:4150, CH1903+ (the geographic of LV95,
in Switzerland) is only connected to ETRS89. See that CH1903+
is in the European tectonic plate, as ETRS89</div>
<div><br>
</div>
<div>A direct transformation is completely ballpark<br>
</div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">echo 42 6 0 2024.6 |
./cs2cs EPSG:9989 EPSG:4150 -d 9 --3d <br>
42.000000000 6.000000000 0.000000000 2024.6</span></div>
<div><br>
</div>
<div>However, from ITRF2020 to ETRS89 there is some change due
to the time (the European plate moving at 2.5 cm/a since
2015):<br>
</div>
<div><span style="font-family:monospace">echo 42 6 0 2024.6 |
./cs2cs EPSG:9989 EPSG:4937 -d 9 --3d <br>
41.999994981 5.999991317 -0.001861237 2024.6</span></div>
<div><br>
</div>
<div>and from ETRS89 to CH1903+ due to the datum offset:<br>
<span style="font-family:monospace">echo 42 6 0 2024.6 |
./cs2cs EPSG:4937 EPSG:4150 -d 9 --3d <br>
42.000742733 6.000670188 -60.682799297 2024.6</span></div>
<div><br>
</div>
<div>Looking at the pipelines, the steps would be ITRF2020 ->
ETRF2020 -> ETRS89 -> CH1903+</div>
<div>(btw, only since PROJ 9.4.1, when ETRF2020 was added)<br>
</div>
<div><br>
</div>
<div>I understand that the only way to get the proper
transformation is chaining these two manually. Via ETRS89 ...
because I know it. Right?</div>
<div><br>
</div>
<div>Well, the future does not look so promising to me: in EPSG
I only see transformations from ITRF2020 to ETRF family,
NAD83(2011) family and NAD83(CSRS)v8. That is Europe, USA and
Canada. That's all, folks.<br>
</div>
<div><br>
</div>
<div>Thanks,</div>
<div>
<div>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr">
<div>.___ ._ ..._ .. . ._. .___ .. __ . _. . __.. ...
.... ._ .__</div>
<div>Javier Jimenez Shaw</div>
<div>Mercator str 42.<br>
</div>
<div>Null-Island<br>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
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</blockquote>
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My software is free, but my time generally not.</pre>
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