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<p>Dear Daniel,</p>
<p>I worked with Martin in those OGC Testbed initiatives.</p>
<p>You may also be interested in OGC 22-035 which documented the use
of the <a href="https://aa.usno.navy.mil/software/novas_info">NOVAS
library</a> to perform conversions between Earth-Centered
Earth-Fixed (ECEF) and Barycentric Celestial Reference System
(BCRS):</p>
<p>
<a class="moz-txt-link-freetext" href="https://docs.ogc.org/per/22-035.html#_cb4841e3-08d7-4a39-bb3f-132f334cbb3c">https://docs.ogc.org/per/22-035.html#_cb4841e3-08d7-4a39-bb3f-132f334cbb3c</a>
(Section 6)<br>
</p>
<p>There's also a brief update on usage of NOVAS the BCRS in section
5 of OGC 23-042:</p>
<p>
<a class="moz-txt-link-freetext" href="https://docs.ogc.org/per/23-042.html#_64ee1661-c316-47f7-9f5b-a0eff8dd170d">https://docs.ogc.org/per/23-042.html#_64ee1661-c316-47f7-9f5b-a0eff8dd170d</a>
(Section 5)</p>
<p>Here's a link to our related demo video for Testbed 19:</p>
<p> <a class="moz-txt-link-freetext" href="https://youtu.be/9ksHTB7S6zQ?t=2983">https://youtu.be/9ksHTB7S6zQ?t=2983</a></p>
<p>Kind regards,</p>
<p>-Jerome</p>
<div class="moz-cite-prefix">On 1/29/25 3:43 PM, Martin Desruisseaux
via PROJ wrote:<br>
</div>
<blockquote type="cite"
cite="mid:7d0465a1-d12e-4930-8a10-081b0d91e0bb@geomatys.com">
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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"> </div>
<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>
</div>
<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>
</div>
</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"
moz-do-not-send="true">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"
moz-do-not-send="true">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"
moz-do-not-send="true">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"
moz-do-not-send="true">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/"
moz-do-not-send="true">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"
moz-do-not-send="true">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>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
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