[IGSMAIL-1502] EOP Comparisons

[D.]

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IGS Electronic Mail      Thu Jan  2 13:11:51 PST 1997      Message Number 1502
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Author: D. McCarthy and B. Luzum
Subject: EOP Comparisons

Following the IERS Gazette 8 (29 October 1996), NEOS has changed
its system of Earth orientation parameters (EOP) to bring the
ITRF and the ICRF into alignment without the use of tabular
values provided in the IERS Annual Reports.  Starting this week,
this tabular correction should no longer be necessary with the
NEOS data.

In keeping with the changes being made, this is an opportunity to
update other aspects of the GPS EOP comparison procedures.  In an
effort to report the most interesting information, we would like
to start providing only the most recent data in the comparisons
of GPS EOPs to the NEOS EOPs.  In short, we would like to
eliminate the first page of our current report and provide only
the second page of comparisons.  In addition, we would propose
not plotting all comparisons of EOPs but only those since the
last change in systems (MJD 50264) when the IGS changed from
ITRF93 to ITRF94.  This should allow for a more homogenous
comparison of data which, in turn, will allow for a better
understanding of the true differences between the individual
contributors data and our combination data.

We would like to make this change as soon as possible.  Please
let us know by 7 January if you see a problem with this
arrangement.
--
Dennis D. McCarthy                       dmc at maia.usno.navy.mil
Director, Directorate of Time            phone: (202) 762-1837
U.S. Naval Observatory                   fax: (202) 762-1563
Washington, DC 20392-5420


[Mailed From: Dennis McCarthy <dmc at Maia.usno.navy.mil>]