[Reference Correction] delaunay2doodson() Formula Citation (IERS 1992 Misattribution)

[MrSoul8715]

Hi,
I’m working on validating the citation for the delaunay2doodson() function in our codebase, which is defined as:

double *delaunay2doodson(const double *const fundarg, double gmst, double *doodson);

The user_guide.txt claims this function’s formula is referenced from [@iers1992, chap. 7, pg. 53-54], but after a thorough review of IERS 1992 documents, no matching formula for converting Delaunay variables to Doodson arguments was found in that chapter/section.

Has anyone else cross-checked the IERS 1992 reference, or have additional sources to confirm the formula lineage? Happy to collaborate on finalizing the correct citation!

Best,
MrSoul8715

[xanthospap]

Hi there,

indeed the formulas can be found in IERS 1992 standards, TN13, Sec. 7, at eq. (3) . pyTMD has the same formulas and claims another reference, but i have no access to that.

IERS 2010 gives the (combined) formula: n⋅β=m(θg​+π)−N⋅F which i guess can be used to validate the above formulas, given that you can find the n's and N's for a tidal constituent --i think there are such tables in IERS 2010--.

May i ask what is the software/codebase you are working on?

best,
Xanthos

[MrSoul8715]

Thank you for your prompt reply. As a student currently engaged in studying the code of the GROOPS project, I have been identifying potential bugs during the learning process. Additionally, I would like to note that I was unable to locate the corresponding formula in IERS1992 TN21, but successfully found it in TN13 as you mentioned. P.S.: The same formula is also implemented in the Doodson class within the GROOPS framework.

[xanthospap]

I see, best of luck with your scientific endeavors. If you think it is interesting and have spare time, do feel free to go through any source code you find in the repository and compare, review and/or find bugs. I would be glad to help with that.