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<p class="MsoNormal"><span lang="EN-GB">Dear list members,<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 work at Dutch NMA responsible for the Dutch national CRS named RDNAP. We recommend the use of PROJ for coordinate transformations, as it uses our official transformation to ETRS89 from EPSG.
<o:p></o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">Horizontal:
<a href="https://epsg.org/transformation_9282/Amersfoort-to-ETRS89-9.html">https://epsg.org/transformation_9282/Amersfoort-to-ETRS89-9.html</a> (and
<a href="https://epsg.org/transformation_9281/Amersfoort-to-ETRS89-8.html">https://epsg.org/transformation_9281/Amersfoort-to-ETRS89-8.html</a>)<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">Vertical:
<a href="https://epsg.org/transformation_9597/ETRS89-to-ETRS89-NAP-height-2.html">
https://epsg.org/transformation_9597/ETRS89-to-ETRS89-NAP-height-2.html</a> (and <a href="https://epsg.org/transformation_9283/ETRS89-to-NAP-height-2.html">
https://epsg.org/transformation_9283/ETRS89-to-NAP-height-2.html</a>)<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">However, I noticed that at the moment PROJ doesn't by default use the transformation we recommend for transformation to ITRF2014.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-GB">RDNAP to ETRF2000:<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">echo 128410.0957 445806.4960 -0.4754 2023.00 | cs2cs epsg:7415 epsg:7931 -d 9<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The result is in accordance with our official transformation:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">52.000000000 5.000000000 43.0000 2023.00<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-GB">RDNAP to WGS84:<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">echo 128410.0957 445806.4960 -0.4754 2023.00 | cs2cs epsg:7415 epsg:4326 -d 9<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The result is a null transformation in accordance with our recommendation:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">52.000000000 5.000000000 43.0000 2023.00<o:p></o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-GB"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b>RDNAP <u>via ETRF2000</u> to ITRF2014:<o:p></o:p></b></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">echo 128410.0957 445806.4960 -0.4754 2023.00 | cs2cs epsg:7415 epsg:7931 -d 9 | cs2cs epsg:7931 epsg:7912 -d 9<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The result is a time-dependant transformation in accordance with our recommendation:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">52.00000<u>5512</u> 5.00000<u>8256</u> 43.0<u>197</u> 2023.00<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-GB">RDNAP to ITRF2014:<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">echo 128410.0957 445806.4960 -0.4754 2023.00 | cs2cs epsg:7415 epsg:7912 -d 9
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The result is a null transformation, which is
<u>not</u> what we recommend:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">52.00000<u>0000</u> 5.00000<u>0000</u> 43.0<u>000</u> 2023.00<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 assume that the best way to fix this is to ask EPSG to link RDNAP to ETRF2000 instead of the ETRS89 datum ensemble. Would that indeed solve the problem in PROJ?<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">Kind regards, Jochem<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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