L. Petrov
Absolute methods for determination of reference system from VLBI observations.
 
                   ABSTRACT
 
 
There are two principal approaches to derivation of a reference system
from various types of observations. Positions of stations and sources can be
determined with respect to the reference frame taken as a fiducial one in
differential approaches. Positions of a subset of some fiducial
stations/sources which ``hold'' the system are fixed and are not estimated
in the framework of this approach. The catalogues built by this way
depend on the values of a priori positions of fiducial objects and therefore
we call them ``differential catalogues''. However method of VLBI allows us to
derive positions of all stations/sources from the observations up to a set of
arbitrary constants. Since the reference system obtained by this way does not
depend on the a priori catalogues it is called ``absolute`` reference system.
Approaches for the development of such absolute catalogues of stations/sources
using VLBI observations are discussed. Consequences on separation vertical
component of station velocities from horizontal components are emphasized.
 
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In Proceedings of the 13th Working Meeting on European VLBI for Geodesy
and Astrometry, Viechtach, 1999
 
Keywords: reference frame, catalogue