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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi Thomas,<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">Using an axisswap between height and time is indeed one of the possible temporary solutions that I tested. However, we will introduce a time-dependent transformation as soon as the time-series
of the GNSS reference station is long enough. So publishing a PROJ pipeline that uses the time for storing a height value now might be confusing for users. I have another temporary solution (applying the same geoid twice) which we could use, but I think that
PROJ should have a more elegant solution for this rather common case.<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">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"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Thomas Knudsen <knudsen.thomas@gmail.com>
<br>
<b>Sent:</b> donderdag 14 december 2023 19:15<br>
<b>To:</b> Lesparre, Jochem <Jochem.Lesparre@kadaster.nl><br>
<b>Cc:</b> PROJ@lists.osgeo.org<br>
<b>Subject:</b> Re: [PROJ] Make push and pop FIFO?<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">If your input data does not need time stamps, you may be able to work around this using +omit_fwd/+omit_inv selectors and a set of axisswap order=1,2,4,3 steps? <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Den tors. 14. dec. 2023 kl. 14.13 skrev Lesparre, Jochem via PROJ <<a href="mailto:proj@lists.osgeo.org">proj@lists.osgeo.org</a>>:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">Hi list members,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">The PROJ operations
</span><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">+proj=push</span><span lang="EN-GB" style="font-size:10.0pt"> and
</span><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">+proj=pop</span><span lang="EN-GB" style="font-size:10.0pt"> use "last in, first out" (LIFO) to store and retrieve coordinate values in a stack. It seems that I need "first in, first out"
(FIFO) or other new functionality in PROJ.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i><u><span lang="EN-GB" style="font-size:10.0pt">Problem</span></u></i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">The Dutch Caribbean islands use TM-projections based on old datums. We have an exact Helmert transformation per island that transforms
the horizontal coordinates to an ITRS realisation at a specific epoch. For some islands we need a geoid (EGM2008 sampled at 45” is the best we have at the moment) for the height transformation from local levelling heights to ITRS. That works fine for a forward
transformation with this PROJ pipeline: </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">cct +proj=pipeline
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=push +v_3
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=tmerc +inv +lat_0=12.180658675 +lon_0=-68.251802281 +k_0=1 +x_0=23209.5600 +y_0=21423.9900 +ellps=intl
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=cart +ellps=intl
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=helmert +x=-366.1939 +y=-115.0688 +z=-776.7039 +rx=20.963080 +ry=16.462749 +rz=-14.276379 +s=-12.80900
+convention=coordinate_frame +exact </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=cart +inv +ellps=GRS80
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=pop +v_3
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=vgridshift +grids=egm2008_0_45.tif +inv
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">However, I do not get exactly the same results for the inverse transformation with
</span><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">-I</span><span lang="EN-GB" style="font-size:10.0pt">, since I apply the geoid on the ITRS coordinates, but then the physical height is used for the Helmert transformation instead of the
correct ellipsoidal height. This gives a small error in the horizontal coordinates in this case, but can easily reach more than 50 metres for other CRSs.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i><u><span lang="EN-GB" style="font-size:10.0pt">Solution</span></u></i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">The most elegant solution seems to me to use FIFO for operations +proj=push and +proj=pop, so I can use this pipeline:</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">cct +proj=pipeline
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=push +v_3
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=tmerc +inv +lat_0=12.180658675 +lon_0=-68.251802281 +k_0=1 +x_0=23209.5600 +y_0=21423.9900 +ellps=intl
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=cart +ellps=intl
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=helmert +x=-366.1939 +y=-115.0688 +z=-776.7039 +rx=20.963080 +ry=16.462749 +rz=-14.276379 +s=-12.80900
+convention=coordinate_frame +exact </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=cart +inv +ellps=GRS80
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=push +v_3</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=pop +v_3
</span></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=vgridshift +grids=egm2008_0_45.tif +inv
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=pop +v_3 +omit_fwd
</span></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i><u><span lang="EN-GB" style="font-size:10.0pt">Alternative</span></u></i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">Another possible solution is a new PROJ operation e.g.
</span><span lang="EN-GB" style="font-size:10.0pt;font-family:Consolas">+proj=flip</span><span lang="EN-GB" style="font-size:10.0pt"> to make the values of a coordinate value and the value stored in the stack switch places.
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">cct -I +proj=pipeline
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=push +v_3
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=utm +zone=19 +inv +ellps=intl
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=cart +ellps=intl
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=helmert +x=-366.1939 +y=-115.0688 +z=-776.7039 +rx=20.963080 +ry=16.462749 +rz=-14.276379 +s=-12.80900
+convention=coordinate_frame +exact </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=cart +inv +ellps=GRS80
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=flip +v_3
</span></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=vgridshift +grids=egm96_15.tif +inv
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas">+step +proj=pop +v_3 +omit_fwd
</span></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:9.0pt;font-family:Consolas"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt">Regards, Jochem</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB" style="font-size:10.0pt"> </span><o:p></o:p></p>
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Op al onze producten en diensten zijn onze algemene leveringsvoorwaarden van toepassing<br>
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If you are not the intended recipient, you are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited.<br>
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