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All<br>
<br>
For anyone interested in learning more about the different
realizations of WGS84 and deriving transformations between the
various realizations of WGS 84 here is information for this article
from the ASCE Journal of Survey Engineering.<br>
<span style="font-size: 10pt; color: black;"> </span>
<p class="MsoNormal"><strong><span
style="font-size:12.0pt;font-family:-apple-system;color:#24292E;background:white"
lang="EN-US">Kelly, K. M.</span></strong><span
style="font-size:12.0pt;font-family:-apple-system;color:#24292E;background:white"
lang="EN-US"> and Dennis, M. L. (2022). Transforming between
WGS84 realizations. <em><span style="font-family:-apple-system">Journal
of Surveying Engineering</span></em>, 148(2). doi: </span><span
lang="EN-US"><a
href="https://doi.org/10.1061/(ASCE)SU.1943-5428.0000389"><span
style="font-size:12.0pt;font-family:-apple-system;background:white">10.1061/(ASCE)SU.1943-5428.0000389</span></a></span></p>
If interested email me and I can share.<br>
<br>
Cheers<br>
Brian<br>
<br>
<div class="moz-cite-prefix">On 1/19/2022 4:06 PM, Greg Troxel
wrote:<br>
</div>
<blockquote type="cite" cite="mid:rmiwnivfhq6.fsf@s1.lexort.com">
<pre class="moz-quote-pre" wrap="">
Kirk Waters - NOAA Federal via PROJ <a class="moz-txt-link-rfc2396E" href="mailto:proj@lists.osgeo.org"><proj@lists.osgeo.org></a> writes:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">I'm sure others with more experience will jump in, but I think the main
issue here is that WGS84 is a family of reference frames that are all based
on the GRS80 ellipsoid. So, the problem doesn't exactly make sense and the
various realizations of WGS84 differ at the cm level. Are you perhaps
trying to go from a NAD83 realization (such as NAD83(2011)) to a WGS84
realization (maybe ITRF14
or something)?
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
I think Kirk has it exactly right.
Also, GRS80 is not a datum, but only a name for an ellipsoid. So
"converting from GRS80" does not make sense.
Further into the weeds, WGS84 realizations are dynamic datums and if you
are talking about coordinates of crust-fixed objects you need to pay
attention to epoch. If you care about a few cm, you really need to pay
attention.
</pre>
<br>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
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<a class="moz-txt-link-freetext" href="https://lists.osgeo.org/mailman/listinfo/proj">https://lists.osgeo.org/mailman/listinfo/proj</a>
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
*************************************
Brian Shaw
Rocky Mountain Regional Advisor (CO, MT, WY)
NOAA's National Geodetic Survey (NGS)
Cell Phone # 240-988-6363</pre>
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