Hello Daniel
Le 2025-01-29 à 20 h 13, Daniel Garcia-Briseno via PROJ a écrit :
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.
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.
The Open Geospatial Consortium (OGC) has conducted TestBeds in 2022 and
2023 on exactly those topics. OGC has published the following
engineering reports:
* 3D+ Data Space Object Engineering Report (23-011r1) —
https://docs.ogc.org/per/23-011r1.pdf
* Reference Frame Transformation Engineering Report (22-038r2) —
https://docs.ogc.org/per/22-038r2.pdf
* Non-Terrestrial Geospatial Engineering Report (23-042) —
https://docs.ogc.org/per/23-042.pdf
* Extraterrestrial GeoTIFF Engineering Report (23-028) —
https://docs.ogc.org/per/23-028.pdf
A more complete list of Testbed engineering reports is at
https://www.ogc.org/completed-cosi-initiatives/
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
(https://docs.ogc.org/as/18-005r8/18-005r8.pdf) 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:
* InertialCRS (you will need this one for referencing relative to the Sun)
* MinkowskyCS (for Einstein's relativity)
* A few others
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.
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.
Please do not hesitate to contact me if you have any question.
Regards,
Martin
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