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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Dear Fabian,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">For this transformation push/pop is not needed. That only makes sense in other situations, like when you use a geoid.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">If the scale factor also differs from the primary source (EPSG is a secondary source), it should be adapted in the example to avoid confusion. If EPSG differs with the primary source,
EPSG should be notified that there might be a mistake in their registry.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Kind regards, Jochem<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b>From:</b> PROJ <proj-bounces@lists.osgeo.org> <b>On Behalf Of
</b>Fabian Gross<br>
<b>Sent:</b> Friday, June 14, 2019 3:41 PM<br>
<b>To:</b> proj@lists.osgeo.org<br>
<b>Subject:</b> [PROJ] How to apply Helmert trafo<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Dear proj-members,</span>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">I would like to apply a Helmert trafo as part of a datum shift.</span>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">The example follows the EPSG geomatics guidance 7/2 (report 373-7-2):</span>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">From WGS72 (</span><span style="font-size:12.0pt;font-family:"Courier New";color:blue">4984</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif">) -> WGS84 (</span><span style="font-size:12.0pt;font-family:"Courier New";color:blue">4978</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif">).</span>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">There are 2 issues:</span>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">1. How to apply Helmert-Trafo? I.e.
</span><o:p></o:p></p>
<ul type="disc">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1">
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">with or </span><o:p></o:p></li><li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1">
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">without the push/pop of the ellipsoidal height.
</span><o:p></o:p></li></ul>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Only if it is not pushed/popped do the values fit to the reference and the direct/naive implementation of Helmert.</span>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">2. The scale parameters in the example (</span><i><span style="font-size:12.0pt;font-family:"Courier New";color:gray">0.219</span></i><span style="font-size:10.0pt;font-family:"Arial",sans-serif">)
and the EPSG catalogue of pyproj (</span><i><span style="font-size:12.0pt;font-family:"Courier New";color:gray">0.2263</span></i><span style="font-size:10.0pt;font-family:"Arial",sans-serif">) do not agree.</span>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Arial",sans-serif">The attached file has the test case.</span>
<br>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Verdana",sans-serif">Kind regards</span>
<br>
<br>
<span style="font-size:10.0pt;font-family:"Verdana",sans-serif">Fabian Gross<br>
Telefon +49 (711) 648 71-995</span><span style="font-size:7.5pt;font-family:"Verdana",sans-serif"><br>
_________________________________________________</span><b><span style="font-size:18.0pt;font-family:"Verdana",sans-serif"><br>
sbp</span></b><span style="font-size:18.0pt;font-family:"Verdana",sans-serif"> </span>
<b><span style="font-size:7.5pt;font-family:"Verdana",sans-serif"><br>
schlaich<br>
bergermann partner</span></b><span style="font-size:7.5pt;font-family:"Verdana",sans-serif"><br>
<br>
Beratende Ingenieure<br>
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_________________________________________________</span><o:p></o:p></p>
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