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Re: [Orekit Users] Fwd: IERS Message No. 353: Anticipated change to the IERS Bulletin A solution
Le 29/03/2018 à 13:58, Ward, Evan a écrit :
> Hi Luc,
>
> On Thu, 2018-03-29 at 09:52 +0200, Luc Maisonobe wrote:
>> Hi all,
>>
>> Here is a message from IERS specifying that Bulletin A will
>> switch soon to ITRF2014.
>>
>> Orekit already supports IERS 2014 and when you build an ITRF frame
>> using FramesFactory.getITRF(IERSConvention, flag), you basically get
>> the ITRF that corresponds to the EOP you load. This means that up
>> to now, if you used BulletinA, you got ITRF 2008 and now you will
>> get ITRF 2014. The conversion from ITRF 2008 to ITRF 2014 was also
>> available using:
>>
>> HelmertTransformation.Predefined.ITRF_2014_TO_ITRF_2008.
>> createTransformedITRF(itrf2008, "ITRF-2008");
>>
>> If you were using EOP 14 C04 files to retrieve EOP, you were already
>> using an ITRF 2014.
>
> Should we update how the ITRF frames are handled for CCSDS files?
> CCSDSFrame currently assumes that FramesFactory.getITRF(...) returns
> ITRF2008. As you mention it will only make a small difference. Perhaps
> updating the JavaDoc would be sufficient.
You are right, I did not think about CCSDS files.
We should add a ITRF2014 entry in the CCSDSFrame enumerate and
probably go with the assumption FramesFactory will now return ITF2014
by default as more EOP files do that.
The best would be to be able to detect by ourselves what EOP we load,
but that seems difficult. If we read EOP XX C04, thats easy as the
file name includes the 08 or 14 part. For Bulletin A we could rely
on the file production date, but I'm not sure they will not at some
time reprocess the files. For Bulletin B I asked months ago if the
underlying EOP were for ITRF 08 or 14 and never received an answer
from IERS. Also IERS has a tendency to change file content without
changing the name. I therefore don't know how we can handle this
in the general case.
The difference is small, at a few millimeters level, but we are
going in the direction of very high accuracy, so we should deal
with this, even if only a few users are concerned.
best regards,
Luc
>
> Best Regards,
> Evan
>
>>
>> In any case, this is only important if you need a very high accuracy.
>>
>> best regards,
>> Luc
>>
>> -------- Message transféré --------
>> Sujet : IERS Message No. 353: Anticipated change to the IERS Bulletin A
>>
>> solution
>> Date : Wed, 28 Mar 2018 18:32:27 +0200 (CEST)
>> De : central_bureau@iers.org <mailto:central_bureau@iers.org>
>> Pour : messages@iers.org <mailto:messages@iers.org>
>>
>> ***********************************************************************
>> *
>> IERS Message No. 353 March 28,
>> 2018
>> ***********************************************************************
>> *
>>
>>
>> Anticipated change to the IERS Bulletin A solution
>>
>>
>> Dear IERS users,
>>
>> As of Bulletin A Vol XXXI, No. 013, on 29 March, 2018, the IERS Rapid
>> Service/Prediction Center will transition the EOP solution to be
>> consistent with the 14 C04 for polar motion, UT1-UTC, and celestial
>> pole
>> offsets. This change will result in a jump of less than 0.1 mas in
>> polar
>> motion and 10 us in UT1-UTC. Small adjustments will be made to the
>> celestial pole offsets from approximately March 2017 to present in
>> order
>> to be more consistent with the 14 C04 solution. The only users who need
>>
>> to be concerned with this change are those who need EOP accuracy to be
>> better than 0.1 mas (~0.3 cm at the Earth's surface, ~1.2 cm at GPS
>> orbit.)
>>
>> A final notice of the anticipated change will be contained near the top
>>
>> of the IERS Bulletin A Vol XXXI, No. 013, on 29 March 2018, where notes
>>
>> to users are placed. Users are strongly encouraged to review this
>> message to confirm the change or to note if the change was not
>> implemented due to technical problems.
>>
>> Kind regards,
>> Nick Stamatakos
>> IERS Rapid Service Prediction Centre:
>> Production director and lead project scientist
>>
>>
>> ***********************************************************************
>> *
>> IERS Messages are edited and distributed by the IERS Central Bureau.
>> If not stated otherwise, the IERS is only the distributor of the
>> message
>> and is not responsible for its content.
>> To submit texts for distribution and to subscribe or unsubscribe,
>> please write to <central_bureau@iers.org <mailto:central_bureau@iers.org>>.
>> Archives: http://www.iers.org/Messages/
>> ***********************************************************************
>> *
>>