[Orekit Developers] ITRF 2014

[MAISONOBE Luc <luc.maisonobe@c-s.fr>]

Hi all,

ITRF 2014 is now the official ITRF implementation
<https://www.iers.org/IERS/EN/Publications/TechnicalNotes/tn38.html;jsessionid=00A1E9E3ED3E794996A2746679BC53E0.live1>.
It seems recent long term EOP files (C04 series) are consistent
with it (see  
<https://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html>).
As usual with IERS, there is still a confusion in file names as
the EOP 14 C04 files consistent with ITRF 2014  
(<http://hpiers.obspm.fr/eoppc/eop/eopc04/>) and
the EOP 08 C04 files consistent with ITRF 2008  
(<http://hpiers.obspm.fr/eoppc/eop/eopc04_08/>)
use the same file names...

I was not able to see if bulletin A, bulletin B and finals.[all,  
daily] files were
consistent with ITRF 2014 or 2008.

The Helmert transformation between ITRF 2014 and ITRF 2008 is available in
the IERS technical note 38 linked above. The difference between these
frames are really small, at millimeter level.

I propose to update Orekit and arbitrarily consider EOP are consistent
with ITRF 2014 (we currently arbitrarily consider they are consistent
with ITRF 2008) and add the new Helmert transformation alongside the
existing predefined ones. We may also consider renaming the class
EOP08C04FilesLoader into EOPC04FilesLoader as it applies to both the
'08' and '14' files.

What do you think?

best regards,
Luc