Technical description of ivs2017a_dsnx:
=======================================
VLBI combination group of the Federal Agency for Cartography and Geodesy (BKG), Germany
(Sabine Bachmann, sabine.bachmann(at)bkg.bund.de, ccivs(at)bkg.bund.de)
March, 2017
The ivs2017a_dsnx series is a combination product by accumulation of normal
equation matrices. The normal equation matrices in these files are
unconstrained (datum-free).
Input series are currently contributed by BKG, CGS, DGFI, GFZ, GSFC, IAA, OPA and USNO.
Analysis center: | Software:
-----+-------------------------------------------------------------+-----------
BKG | Bundesamt fuer Kartographie und Geodaesie, Leipzig, Germany | CALC/SOLVE
CGS | Centro di Geodesia Spaziale, Italy | CALC/SOLVE
DGFI | Deutsches Geodaetisches Forschungsinstitut, Munich, Germany | OCCAM/DOGS_RI
GFZ | German Research Center for Geosciences | VieVS@GFZ
GSFC | Goddard Space Flight Center, Washington D.C., USA | CALC/SOLVE
IAA | Institute of Applied Astronomy RAS, Russia | QUASAR
OPA | Paris Observatory, Paris, France | CALC/SOLVE
USNO | U.S. Naval Observatory, Washington D.C., USA | CALC/SOLVE
-----+-------------------------------------------------------------+-----------
Purpose of this solution:
=========================
The main objective of ivs2017a_dsnx is to provide IVS combination ofthe rigorous
determination of station positions and earth orientation parameters.
Detailed description:
=====================
This approach of combining VLBI solutions is based on the principle of
addition of normal equation matrices and thus begins at an earlier step of
analysis. This approach is also known as "Adjustment of groups of observations".
This approach uses datum-free normal equation matrices of VLBI sessions which
are provided as SINEX files.
The combination is performed in the following way:
Apriori epochs:
---------------
Before accumulating the individual normal equation matrices the matrices are
transformed to the mean epoch of all contributions (they may differ by a few
minutes) by using the respective EOP rates.
Apriori values:
---------------
Furthermore the individual normal equation matrices have to be transformed to
a common set of apriori values. For station coordinates a TRF (aligned to ITRF2014) computed from all SINEX
files available between 1979 and today, for the earth orientation parameters the 14C04
values are used as apriori values for the normal equation matrices of all analysis centers.
These values are listed in the SOLUTION/APRIORI-block.
Generation of SINEX file for accumulated solution:
--------------------------------------------------
After applying scaling factors the normal equation matrices of the individual
solutions are accumulated. The resulting normal equation matrix is then written
into a new SINEX file (DATABASE_CODE_ivs2017a.snx).
Since the original normal equation matrices are datum-free or singular, the
accumulated normal equation matrices are still datum-free. So there is no
SOLUTION/ESTIMATE section in this file, since no datum information has been
imposed.
Estimated parameters:
=====================
Parameters combined are:
ALL station coordinates, x-pole, y-pole, UT1-TAI, x-pole-dot, y-pole-dot, LOD, dX, dY.
As mentioned before there are no estimated parameters at all since there is
no datum information imposed.
Software:
=========
- The processing of the individual matrices is done using a software from
the German Geodetic Research Institute (DGFI), Munich, called DOGS-CS.
- A software called combine_sinex has been developed initially at the Geodetic Institut
of the University of Bonn and adapted at the Federal Agency for Cartography and Geodesy
(BKG) and is used to process the input SINEX files, perform checks of the input data,
to compute scaling factors and to visualize results.
Contact:
========
Federal Agency for Cartography and Geodesy (BKG)
VLBI combination Group
Richard-Strauss-Allee 11
D-60598 Frankfurt am Main
Germany
eMail: sabine.bachmann(at)bkg.bund.de or
ccivs(at)kg.bund.de
website: ccivs.bkg.bund.de