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<p>Alain,</p>
<p>you actually want to do 2 things:</p>
<p>- change the reference frame (from ITRF92 to ITRF2014)<br>
</p>
<p>- and change of coordinate epoch in one of the coordinate frames
(presumably in ITRF2014)<br>
</p>
<p>You can't do that just by using the 15-parameter
ITRF92->ITRF2014 transformation.</p>
<p>So first step, change from ITRF92 to ITRF2014 at epoch 1993.0.
You must use +t_epoch=2010 as it is the canoncial central epoch of
the transformation<br>
</p>
<p>$ echo -139.57736536 -8.95162075 2.234 1993.0 | cct -d 8
+proj=pipeline +step +proj=cart +ellps=GRS80 +step +proj=helmert
+x=-0.0154 +y=-0.0015 +z=0.0708 +rx=0 +ry=0 +rz=-0.00026
+s=-0.00309 +dx=-0.0001 +dy=0.0005 +dz=0.0033 +drx=0 +dry=0
+drz=-2e-05 +ds=-0.00012 +t_epoch=2010 +convention=position_vector
+step +inv +proj=cart +ellps=GRS80<br>
-139.57736535 -8.95162059 2.24172393 1993.0000<br>
</p>
<p>You can also that by using EPSG objects (but using lat, long
order)</p>
<p>$ echo -8.95162075 -139.57736536 2.234 1993.0 | cs2cs -d 8
ITRF92 ITRF2014<br>
-8.95162059 -139.57736535 2.24172393 1993.0<br>
<br>
</p>
<p>and second step, apply the Pacific plate motion Helmert
transformation for ITRF2014:</p>
<p>$ echo -139.57736535 -8.95162059 2.24172393 2023 | cct
-d 8 \<br>
+proj=pipeline +step +proj=cart +ellps=GRS80 \<br>
+step +init=ITRF2014:PCFC +t_epoch=1993 \<br>
+step +inv +proj=cart +ellps=GRS80<br>
-139.57738390 -8.95161168 2.24071029 2023.0000<br>
<br>
The ITRF2014:PCFC parameters are at
<a class="moz-txt-link-freetext" href="https://github.com/OSGeo/PROJ/blob/4762020db550ac3b9405970f8830abdb5fefdb48/data/ITRF2014#L51">https://github.com/OSGeo/PROJ/blob/4762020db550ac3b9405970f8830abdb5fefdb48/data/ITRF2014#L51</a></p>
<p>If inlined:<br>
</p>
<p>$ echo -139.57736535 -8.95162059 2.24172393 2023 | cct -d
8 +proj=pipeline +step +proj=cart +ellps=GRS80 +step +proj=helmert
+drx=-0.000409 +dry=0.001047 +drz=-0.002169
+convention=position_vector +t_epoch=1993 +step +inv +proj=cart
+ellps=GRS80<br>
-139.57738390 -8.95161168 2.24071029 2023.0000<br>
<br>
</p>
<p>The difference between the initial and final coordinate in
ITRF2014 is 2.272 m.<br>
</p>
<p>$ echo -8.95162075 -139.57736536 -8.95161168 -139.57738390 |
geod -I +ellps=GRS80<br>
</p>
<p>-63d48'8.651" 116d11'51.359" 2.272<br>
<br>
</p>
<p>You could actually concatenate the 2 pipelines by using the
+proj=set +v_4=2023 operator to force the target epoch of the
plate motion transformation<br>
</p>
<p>$ echo -139.57736536 -8.95162075 2.234 1993.0 | cct -d 8
+proj=pipeline \<br>
+step +proj=cart +ellps=GRS80 \<br>
+step +proj=helmert +x=-0.0154 +y=-0.0015 +z=0.0708 +rx=0
+ry=0 +rz=-0.00026 +s=-0.00309 \<br>
+dx=-0.0001 +dy=0.0005 +dz=0.0033 +drx=0 +dry=0
+drz=-2e-05 +ds=-0.00012 +t_epoch=2010 +convention=position_vector
\<br>
+step +proj=set +v_4=2023 \<br>
+step +proj=helmert +drx=-0.000409 +dry=0.001047
+drz=-0.002169 +convention=position_vector +t_epoch=1993 \<br>
+step +inv +proj=cart +ellps=GRS80<br>
<br>
-139.57738390 -8.95161168 2.24071029 2023.0000<br>
<br>
Even<br>
</p>
<div class="moz-cite-prefix">Le 15/11/2022 à 17:16, Alain Orsoni a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:BF958EC8-67F1-432E-AFE0-C0AD9BE89B00@ign.fr">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Hello,
<div class=""><br class="">
</div>
<div class="">I’m trying to convert ITRF92 (epoch 93.0)
coordinates to ITRF2014 epoch 2023.0.</div>
<div class="">Having some 8 cms per year movement I expect some
2.4m difference in the coordinates.</div>
<div class=""><br class="">
</div>
<div class="">I tried some syntaxes but did not understand clearly
how (where) to indicate the epochs (initial and final) in my
tests :</div>
<div class=""><br class="">
</div>
<div class="">One test applied was :</div>
<div class=""><br class="">
</div>
<div class="">
<div style="margin: 0px; font-stretch: normal; font-size: 11px;
line-height: normal; font-family: Menlo;" class=""><span
style="font-variant-ligatures: no-common-ligatures" class="">echo
-139.57736536 -8.95162075 2.234 2023.0 | cct
+proj=pipeline +step +proj=cart +ellps=GRS80 +step
+proj=helmert +x=-0.0154 +y=-0.0015 +z=0.0708 +rx=0 +ry=0
+rz=-0.00026 +s=-0.00309 +dx=-0.0001 +dy=0.0005 +dz=0.0033
+drx=0 +dry=0 +drz=-2e-05 +ds=-0.00012 +t_epoch=1993
+convention=position_vector +step +inv +proj=cart
+ellps=GRS80</span></div>
</div>
<div class=""><br class="">
</div>
<div class="">Which gave me </div>
<div class="">
<div style="margin: 0px; font-stretch: normal; font-size: 11px;
line-height: normal; font-family: Menlo;" class=""><span
style="font-variant-ligatures: no-common-ligatures" class="">-139.5773658008
-8.9516192265 2.1701 2023.0000</span></div>
</div>
<div class=""><br class="">
</div>
<div class="">As result. Difference much lower than expected
representing some 20 cm variation from one epoch to the other.</div>
<div class=""><br class="">
</div>
<div class="">I indicated the final epoch desired in my input and
the initial epoch in the helmert transform.</div>
<div class="">This is probably false, but I did not encounter this
kind of indication in the documentation.</div>
<div class=""><br class="">
</div>
<div class="">Where is the misunderstanding?</div>
<div class=""><br class="">
</div>
<div class="">Thank you for any help,</div>
<div class=""><br class="">
</div>
<div class="">Alain Orsoni</div>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
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</pre>
</blockquote>
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