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<p class="moz-cite-prefix">Hello Daniel<br>
</p>
<p class="moz-cite-prefix">Le 2025-01-29 à 20 h 13, Daniel
Garcia-Briseno via PROJ a écrit :<br>
</p>
<blockquote type="cite"
cite="mid:01000194b37baadd-dee0bd08-78c3-4746-9833-50210ab88dd1-000000@email.amazonses.com">
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<div class="signature-div">I'm a software developer on a NASA
contract, I'm working on a web based platform that pulls
data from various providers in different coordinate systems,
but not all my coordinates are earth based. I recently
discovered proj4js which led me to you.</div>
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<div class="signature-div"> </div>
<div class="signature-div">Throughout your documentation there's
a lot of "geo", but my data is a mix of "geo" and "helio"
where my coordinates are relative to the sun, not the earth.
Is there a way I could use proj to transform between
earth-relative and sun-relative coordinates? I need to convert
between a geocentric system and heliocentric system.</div>
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</blockquote>
<p>The Open Geospatial Consortium (OGC) has conducted TestBeds in
2022 and 2023 on exactly those topics. OGC has published the
following engineering reports:</p>
<ul>
<li>3D+ Data Space Object Engineering Report (23-011r1) —
<a class="moz-txt-link-freetext" href="https://docs.ogc.org/per/23-011r1.pdf">https://docs.ogc.org/per/23-011r1.pdf</a><br>
</li>
<li>Reference Frame Transformation Engineering Report (22-038r2) —
<a class="moz-txt-link-freetext" href="https://docs.ogc.org/per/22-038r2.pdf">https://docs.ogc.org/per/22-038r2.pdf</a></li>
<li>Non-Terrestrial Geospatial Engineering Report (23-042) —
<a class="moz-txt-link-freetext" href="https://docs.ogc.org/per/23-042.pdf">https://docs.ogc.org/per/23-042.pdf</a></li>
<li>Extraterrestrial GeoTIFF Engineering Report (23-028) —
<a class="moz-txt-link-freetext" href="https://docs.ogc.org/per/23-028.pdf">https://docs.ogc.org/per/23-028.pdf</a><br>
</li>
</ul>
<p>A more complete list of Testbed engineering reports is at
<a class="moz-txt-link-freetext" href="https://www.ogc.org/completed-cosi-initiatives/">https://www.ogc.org/completed-cosi-initiatives/</a></p>
<p>Those engineering reports review some theoretical concepts about
referencing in space and mention some existing software such as
NASA SPICE. Then, they review how the OGC Topic 2 / ISO 19111
standard (<a class="moz-txt-link-freetext" href="https://docs.ogc.org/as/18-005r8/18-005r8.pdf">https://docs.ogc.org/as/18-005r8/18-005r8.pdf</a>) can be
used for the definition of CRS in space. Those reports identify
the following classes which would need to be added to the existing
international standards:</p>
<ul>
<li>InertialCRS (you will need this one for referencing relative
to the Sun)<br>
</li>
<li>MinkowskyCS (for Einstein's relativity)</li>
<li>A few others</li>
</ul>
<p>Above-cited classes are not yet approved standards. However, they
are on the agenda for discussion in the ISO 19111 working group.
It may take a few years before they appear in standards, if
accepted. A proposal for encoding images in space in the GeoTIFF
format has also been submitted, but I think that the OGC GeoTIFF
working group will want to take a different approach than the one
proposed in the last engineering report.<br>
</p>
<p>A prototype exists for the CRS in space and the GeoTIFF
extension. As a proof of concept, the TestBed implemented a
scenario with the NASA DART mission, where a satellite
intentionally collided with an asteroid for measuring the
trajectory change. A chain of coordinate operation from Earth to
the satellite's moon has been implemented using ISO 19111 +
above-cited extensions. More details in above engineering reports.</p>
<p>Please do not hesitate to contact me if you have any question.</p>
<p> Regards,</p>
<p> Martin</p>
<p><br>
</p>
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