[IGSMAIL-5455]: IGS05 Fine Tuning

[Ferland, Rémi]

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IGS Electronic Mail      03 Nov 07:51:01 PST 2006      Message Number 5455
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Author:  R. Ferland

Dear colleagues,

	Following several feedbacks received the last couple of weeks,
I am proposing minor last minute "fine tuning" to the IGS realization
of ITRF2005. 4 stations are affected:

Addition:
=========

CORD:	This station was in earlier proposed realizations. It had
	been removed because the station was decommissioned.
	The station will be recommissioned and the same equipment
	will be reinstalled! (D. Stowers).
	This is conditional to the coordinates time series resumes
	without discontinuity.

LHAZ	To replace LHAS (a few meters away) suggested by R. Stoeger.
	At the site all ACs have been using one or the other.
	2 ACs have been using LHAZ regularly.

Deletion:
=========

GOUG	Data problems. Likely difficult to improve in the
	short term due to the remoteness of the station.

FAIR	Due to the gradual degradation of the residuals (mainly in
	the North/South component). The cause is likely related to
	non-linear motion due to post-seismic effects caused by the
	Delani earthquake.

	Those deletions are very unfortunate as the two stations
have some very desirable characteristics.

Other Stations:
===============

	The coordinates & velocity changes of the other stations
between the current and updated proposed realization are unchanged
(<< 0.1mm & << 0.1mm/y). This applies to both versions of the
realization IGS05 & IGT05.
The total number of stations in remains 132.

The update can be found at the usual location:

ftp	macs.geod.nrcan.gc.ca
cd	/pub/requests/sinex/IGS05


Transformations:
================

	For those of you who may want the transformation from
IGS05 (with absolute antenna phase center) and IGb00 (relative
antenna phase center) they are (at epoch 2000.0):

   R X (mas)   :              -0.0070
   R Y (mas)   :               0.0340
   R Z (mas)   :              -0.0069
   T X (m)     :              -0.0003
   T Y (m)     :              -0.0015
   T Z (m)     :              -0.0061
   SCL (ppb)   :               0.7125
 d R X (mas/y) :               0.0033
 d R Y (mas/y) :              -0.0001
 d R Z (mas/y) :              -0.0161
 d T X (m/y)   :              -0.0004
 d T Y (m/y)   :               0.0007
 d T Z (m/y)   :              -0.0018
 d SCL (ppb/y) :               0.1748

	Note that the transformation of the IGS realization,
using relative phase center only, they have been provided
in the earlier e-mail (Sect. 4-1):
http://igscb.jpl.nasa.gov/mail/igsmail/2006/msg00170.html

A comparison of the two sets of transformations indicates
that the phase center change causes variations in the
transformations:
	Rotations	< 0.02mas,
	Translation	< 1mm,
	Scale		< 0.2ppb
The effect on the rates is negligible.

	Starting with GPS week 1400, the "parallel" solutions
using the absolute phase center provided by the ACs will
become the official solutions. This imply that there won't
be any combination for those parallel solutions posted
at the usual ftp.

The cooperation of all those that have been contributing to this
long transition phase is very much appreciated!
Thanks also to all of those that have been providing feedback
on the various versions of the proposed realization!

Sorry for any inconveniences,
Best Regards,
Remi,