Dear Daniel,
I worked with Martin in those OGC Testbed initiatives.
You may also be interested in OGC 22-035 which documented the use of the
NOVAS library <https://aa.usno.navy.mil/software/novas_info> to perform
conversions between Earth-Centered Earth-Fixed (ECEF) and Barycentric
Celestial Reference System (BCRS):
https://docs.ogc.org/per/22-035.html#_cb4841e3-08d7-4a39-bb3f-132f334cbb3c
(Section 6)
There's also a brief update on usage of NOVAS the BCRS in section 5 of
OGC 23-042:
https://docs.ogc.org/per/23-042.html#_64ee1661-c316-47f7-9f5b-a0eff8dd170d
(Section 5)
Here's a link to our related demo video for Testbed 19:
https://youtu.be/9ksHTB7S6zQ?t=2983
Kind regards,
-Jerome
On 1/29/25 3:43 PM, Martin Desruisseaux via PROJ wrote:
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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