IERS Message No. 16: IERS Analysis Coordination

central_bureau at central_bureau at
Tue Nov 27 09:51:09 UTC 2001

IERS Message No. 16                                       November 27, 2001

IERS Analysis Coordination

Dear Colleagues,

At the IERS Directing Board Meeting in Brussels in October I took over
the responsibilities of the IERS Analysis Coordinator. This was made
possible by the fact that two positions are now available at my
institute for the tasks of the Analysis Coordinator and for the
Combination Research Center activities.

The two persons who are now working with me in this field are:

  Robert Dill             (dill at
  Daniela Thaller         (daniela.thaller at

Robert Dill will mainly support the IERS AC work, whereas Daniela
Thaller will mainly be working on CRC issues.

The following actions have already been initialized or are planned for
the next few months:

A. Coordination of the CRC Activities

(1) Mail Exploder and Web-Pages

An e-mail exploder has been set up by the IERS Central Bureau for the
exchange of information between the CRCs and other interested groups and
may be used by any person interested to share results, problems, ideas
in the field of combination research within the IERS. The address is

                    crc_forum at

If you wish to receive the e-mails distributed by this exploder, please
send an e-mail to Alexander Lothhammer at the IERS Central Bureau

                   lothhammer at

If you wish to distribute an e-mail of yours to this list, just send it
to crc_forum at

A web page has been established for the IERS Analysis Coordinator
activities at

This web page will be maintained to reflect the goals and projects of
the IERS Analysis Coordinator and the CRC activities.

(2) SINEX-Format

Starting with the IGS SINEX format description (Version 1.00) Daniela
Thaller has put together a new version (Version 2.0) of the SINEX format
including all the additions and modifications of the IVS and ILRS
groups. The SINEX document together with a list of questions concerning
the new version will be distributed to the Technique Coordinators of the
IGS, IVS and ILRS for feedback and comments in the next few days.
Interested groups may have a look at the format description available on
the new web page mentioned above. With this step we hope to ensure that
only one consistent format is followed by all the space techniques. As
soon as the format definitions are finalized we will write a SINEX
checker program that will be available for all groups to check their
SINEX files in order to meet the format definition. We also intend to
put together some guidelines on how SINEX files should be generated to
make sure that a combination is possible without problems. Issues are
e.g. how to handle constraints on the ERPs (UT1 for satellite
techniques, continuity between ERPs of subsequent days, velocity
constraints between collocated sites for ITRF submissions, etc.).

(3) SINEX Data Pool

In order to test and develop their combination software packages the
CRCs need to have access to a broad variety of SINEX files from
different techniques. We therefore plan to establish a pool of SINEX
files or links to SINEX file archives for the CRC activities. This pool
will contain

- all the contributions of the individual analysis centers to the
  ITRF2000 solution together with all the local tie information
- SINEX files of the IGS and its combination centers
- SINEX files from the ILRS and IVS pilot project to the extent available

These SINEX files are thought to allow first tests and to modify the
combination software packages to deal with the SINEX files produced by
different techniques.

(4) "Weekly" SINEX Campaign

It is also planned to come up with a time interval (according to the
Technique Analysis Coordinators) for which the different techniques will
deliver SINEX files for combination research, containing site
coordinates and ERPs. The time interval covered by one SINEX file of the
various techniques should be compatible (e.g. 1 week for GPS, 1 24-h
session for VLBI and 1 or 2 weeks for SLR).

These SINEX files will allow to

- study the consistent combination of coordinates and ERP stemming
  from different techniques
- detect and analyze systematic biases between the results of the
  different techniques
- produce and compare time series of the different techniques
- develop algorithms to allow the production of combined multi-year
  solutions with consistent site coordinates, site velocities and ERPs
- study weighting strategies and datum definition strategies.

These developments will be important steps in the direction of a
rigorous combination of ITRF, ICRF and ERPs in the future.

B. IERS Campaign to align EOPs to ICRF/ITRF2000

This campaign was proposed by Jim Ray with the following objectives:

- generate EOP series with the highest possible consistency with ICRF
  and ITRF2000
- achieve overall accuracy of 0.1 mas
- understand the origin of systematic errors between EOP series of
  different ACs

This campaign is thought to improve the consistency of the IERS products
even before a rigorous combination of ITR/ICRF/EOPs becomes possible.

The details of the campaign and the implementation plan are described on
the new web pages of the IERS Analysis Coordinator.

C. IERS Product Quality

The IERS AC will start to look into the quality of the present IERS
products. This task will consist of:

- putting together a complete list of the IERS products and their
  methods of generation, their availability, accuracy, etc.
- assessing the status of the global network of fundamental stations
- compile a list of the processing standards used by the analysis
  centers and the consistency with the IERS conventions
- check the level of documentation of the IERS products and the
  guidelines about the use of the products

Besides these topics the IERS AC plans a routine quality check of the
IERS products.

More details may be found on the web pages.

We are looking forward to any feedback concerning the activities
proposed here, the web pages, etc.

With best regards,

Markus Rothacher, Robert Dill, and Daniela Thaller
The IERS Analysis Coordination Team

Prof. Dr. Markus Rothacher
Forschungseinrichtung Satellitengeodaesie
Technische Universitaet Muenchen
Arcisstrasse 21
D-80290 Muenchen / Germany
Phone : ++49-89-289-23191
Fax   : ++49-89-289-23178
E-mail: markus.rothacher at

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