[IGSMAIL-1829] CODE Analysis Changes
T.A.
T.A.
Fri Mar 13 06:14:41 PST 1998
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IGS Electronic Mail Fri Mar 13 6:14:41 PST 1998 Message Number 1829
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Author: T.A. Springer
Subject: CODE Analysis Changes
Dear IGS colleagues,
Starting this week a number of (IGS) processing "standards"
have been changed.
For the CODE analysis this means the following changes:
- Reference frame changes:
- ITRF96 coordinates,
- ITRF96 velocity field,
- Use of a subset of 37 of the new set of 47 feference stations
The 11 feference sites not used:
--------------------------------
TROM: No data. Receiver and Antenna are being replaced(?)
NYAL: No data. Receiver and Antenna are being replaced(?)
MADR: Site no longer used due to severe data problems in 1997
MASP: Strong 14-day periods in our solutions
MALI: 40 mm U difference between ITRF96 and CODE
FAIR: 20 mm U difference between ITRF96 and CODE
GODE:-20 mm U difference between ITRF96 and CODE
TIDB: 25 mm U difference between ITRF96 and CODE
OHIG:-18 mm N difference between ITRF96 and CODE
DAV1:-10 mm N difference between ITRF96 and CODE
KERG:-12 mm E difference between ITRF96 and CODE
The 37 sites which are constrained (1 mm):
------------------------------------------
ALGO AREQ BRAZ BRMU DRAO FORT GOLD GRAZ GUAM HART HOB2 IRKT
KIT3 KOKB KOSG KOUR KWJ1 LHAS MAC1 MATE MDO1 NLIB ONSA PERT
PIE1 POTS REYK SANT SHAO THU1 TSKB VILL WES2 WTZR YAR1 YELL
ZWEN
**** Note that we selected one additional site: REYK
- The ITRF96 reference frame is realized by constraining the
positions of the 37 selected sites to 1 mm (this used to be
0.1 mm). This means that the sites may actually move by
several millimeters.
- Site coordinate model change:
- Ocean loading (finally) included based on values from
Dr. H.G. Scherneck.
Estimated CODE product changes
==============================
We estimated the changes in our products (orbits, coordinates
and ERPs) caused by the above modification, by processing five days
with the old and the new strategy (day 060-064 of 1998).
The consistency between the results is very high as you can
see from the table below.
DX DY DZ RX RY RZ SCALE RMS
(mm) (mm) (mm) (mas) (mas) (mas) (ppb) (mm)
CRD 060 NEW-OLD 0 -3 -6 -0.1 -0.0 -0.3 0.5 8.9
CRD 061 NEW-OLD -2 -1 -4 -0.1 -0.0 -0.3 0.4 8.8
CRD 062 NEW-OLD -1 -1 -4 -0.1 -0.0 -0.3 0.4 8.3
CRD 063 NEW-OLD 1 -2 -4 -0.1 -0.0 -0.3 0.3 7.9
CRD 064 NEW-OLD 3 -3 -3 -0.1 -0.0 -0.2 0.1 7.5
ORB 060 NEW-OLD 2 2 1 0.23 -0.11 -0.40 0.1 20.0
ORB 061 NEW-OLD 0 1 4 0.17 -0.13 -0.40 0.0 20.0
ORB 062 NEW-OLD 1 2 6 0.14 -0.06 -0.37 0.0 20.0
ORB 063 NEW-OLD 2 0 5 0.10 -0.02 -0.38 0.0 10.0
ORB 064 NEW-OLD 0 -2 2 0.13 -0.03 -0.34 0.0 10.0
ERP 060-064 NEW-OLD 0.07 -0.17
As noted already by the ACC (Jan Kouba) the change from ITRF94 to
ITRF96 causes small rotations around Y (-0.2 mas) and Z (-.2 mas).
Both effects can clearly be seen in our orbit (ORB) and
ERP results above (note the RX and RY have a
different meaning for the orbit than for the ERPs).
The Z-rotation is also clearly observed in the coordinate (CRD)
differences. The CRD results also show a small scale difference
which indicates that the scale between ITRF94 and ITRF96 is
slightly different, or at least that our realization of the
two ITRF's is different.
The entire CODE ERP series from day 200/1993 to today has been
recomputed using the above reference frame realization. Over the
entire period of 4.5 years the offset between the ITRF94 and
ITRF96 series are:
- X (ITRF96-ITRF94) : -0.037 mas
- Y (ITRF96-ITRF94) : -0.075 mas
- LOD (ITRF96-ITRF94) : -0.004 md/day
An updated AC questionaire (CODE.ACN) has been send to the IGSCB and the
ACC. It is also available on our anonymous ftp (directory CODE).
Kind regards,
Tim Springer, Markus Rothacher and Stefan Schaer
CODE Analysis Center
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Tim Springer Astronomical Institute, University of Berne
Tel: +41 31 6318592 Sidlerstrasse 5, CH-3012 Bern, Switzerland
Fax: +41 31 6313869 ftp: ubeclu.unibe.ch -or- 130.92.6.11
e-mail: springer at aiub.unibe.ch after login: cd aiub$ftp
www: http://www.cx.unibe.ch/aiub/
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[Mailed From: TIM SPRINGER <SPRINGER at aiub.unibe.ch>]
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