Repository navigation
Further precision improvements for earth-centred transformations #11110
Description
With the help of @mkbrewer, a series of PRs has ensured that our earth-centred transforms are now at the level of precision offered by the SOFA/ERFA routines. This issue is to track possible further improvements which may come about by comparison with other, accurate codes (e.g., CALC11):
- Include the effects of free core nutation provided by the
dXanddYvalues given in the IERS tables. For a good introduction to these effects see Chapter 5 of https://www.iers.org/IERS/EN/Publications/TechnicalNotes/tn36.html (from Update precision test of AltAz computation. #11103 (comment))
Activity
ludwigschwardt commentedon Dec 21, 2020
I've been eagerly following these developments, as I'm in the process of switching to Astropy for our radio interferometer delays within the katpoint package. I'm also continuously comparing against CALC11 and trying to squeeze out the maximum reasonable precision.
@mhvk, you would probably be interested in https://gitlab.com/ska-telescope/almacalc/. It's not quite ready for wider release (for one, the license and copyright are probably wrong) but you are welcome to give it a spin 😄 And I would very much like to compare notes.
mhvk commentedon Dec 22, 2020
@ludwigschwardt - thanks! Indeed, over at #10737 (comment), @Jan-Willem alerted me to his package that similarly wraps
almacalc. I also started my own wrapping experiments over at https://github.com/mhvk/pycalc11 based on what is included in DiFX (mostly as I want to be sure I compare to code where no simplifications are made because telescopes are "nearby"; e.g., I thinkalmacalcneglects tidal effects - which of course astropy does not have either but would be important to include to have a best possible reference). And there are other efforts too (see #10737 (comment)) - in short, it seems the time is ripe to ensure we get it working correctly!