Subject: DORIS station discontinuities
From: Pascal Willis <[email-masked]>
To: IDS_Analysis_Forum <[email-masked]>
Date: Fri, 10 Jun 2005 07:37:51 -0700

Dear Martine,

thank you for your contribution. We can now start some useful 
discussion on these aspects

AREA There was an Earthquake after June 23, 2001 (50 cm 
displacement). Furthermore, after the Earthquake the motion is 
non-linear for quite some time (as confirmed by GPS time series). The 
DORIS solution for AREA after this Earthquake must not been used in 
CATREF (unless you use a filter instead of linear model per 
segments). The fact that the INASAN still provide results will alter 
results from all solutions in the combination. This was presented 
several time before

The period of observations to be deleted is also an important part of 
information for the ITRF2004 because if one group release results 
during these periods and not the others, this will affect everybody.

I think you should add something on your Web page as well. See some 
proposals in the following article

Defining a DORIS core network for Jason-1 Precise Orbit Determination 
based on ITRF2000, Methods and realization, P. Willis, J.C. Ries, J. 
of Geod., 2005, in press.

FAIB there is a discontinuity of about -5 cm in latitude after the 
Earthquake of November 3, 2002. This is document in the following 
article (in  press for the past 2 years, sorry)

DORIS as a potential part of a Global Geodetic Observing System, P. 
Willis, Y Bar-Sever, G. Tavernier, in GGOS Science Rationale, H. 
Drewes (Ed.), J. of Geodyn., in press

as discussed in this document, this is confirmed by GPS observation as well

TRIB there was an Earthquake on July 31, 2004. I  do not understand 
your question mark

The major point is that when there is a doubt it is always better to 
put a break in  the analysis because you have the possibility after 
the computation to look at the discontinuity amplitude and constrain 
it to be zero. If you don't put a discontinuity and there is one, you 
are in big trouble. So, in my opinion, the "wait for more 
confirmation" is going to be a problem. Your list should be the sum 
of all discontinuities found by ACs + discontinuities found by 
yourselves. Of course the fact that all groups agree or not on the 
discontinuity is an important piece of information

Looking forward answers from other groups
Pascal
-- 
Pascal Willis
Jet Propulsion Laboratory, MS 238-646     Ph : 1-818-393-4748
4800 Oak Grove Drive                      FAX: 1-818-393-4965
Pasadena CA 91109                         Em : [email-masked]