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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> Looking at the pipelines, the steps would be ITRF2020 -> ETRF2020 -> ETRS89 -> CH1903+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am pretty sure Switzerland uses ETRF2000 as ETRS89 realisation, not ETRF2020. So, the correct transformation would be:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">ITRF2020 -> ETRF2000 -> ETRS89 -> CH1903+</span><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The difference between ETRF2000 and ETRF2020 is about 7 cm. ETRF2000 is recommended for use by national mapping agencies.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Jochem<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></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"> PROJ <proj-bounces@lists.osgeo.org>
<b>On Behalf Of </b>Javier Jimenez Shaw via PROJ<br>
<b>Sent:</b> dinsdag 27 augustus 2024 19:30<br>
<b>To:</b> proj <PROJ@lists.osgeo.org><br>
<b>Subject:</b> [PROJ] Transformations in ITRF2020<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">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)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The point is when the destination CRS does not have a direct transformation from ITRF2020 (or almost).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">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<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">A direct transformation is completely ballpark<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">echo 42 6 0 2024.6 | ./cs2cs EPSG:9989 EPSG:4150 -d 9 --3d
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42.000000000 6.000000000 0.000000000 2024.6</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">However, from ITRF2020 to ETRS89 there is some change due to the time (the European plate moving at 2.5 cm/a since 2015):<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">echo 42 6 0 2024.6 | ./cs2cs EPSG:9989 EPSG:4937 -d 9 --3d
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41.999994981 5.999991317 -0.001861237 2024.6</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">and from ETRS89 to CH1903+ due to the datum offset:<br>
<span style="font-family:"Courier New"">echo 42 6 0 2024.6 | ./cs2cs EPSG:4937 EPSG:4150 -d 9 --3d
<br>
42.000742733 6.000670188 -60.682799297 2024.6</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Looking at the pipelines, the steps would be ITRF2020 -> ETRF2020 -> ETRS89 -> CH1903+<o:p></o:p></p>
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<p class="MsoNormal">(btw, only since PROJ 9.4.1, when ETRF2020 was added)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I understand that the only way to get the proper transformation is chaining these two manually. Via ETRS89 ... because I know it. Right?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">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.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks,<o:p></o:p></p>
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<p class="MsoNormal">.___ ._ ..._ .. . ._. .___ .. __ . _. . __.. ... .... ._ .__<o:p></o:p></p>
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<p class="MsoNormal">Javier Jimenez Shaw<o:p></o:p></p>
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<p class="MsoNormal">Mercator str 42.<o:p></o:p></p>
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<p class="MsoNormal">Null-Island<o:p></o:p></p>
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