Research Information System
7th VieVS User Workshop, Viyana, Austria, 14 - 15 September 2016, pp.1
In VLBI (Very Long Baseline Interferometry) analysis, prior information is added to model auxiliary parameters in order to perform or stabilize the parameter estimation. The gradients are the only auxiliary parameters, which are usually directly constrained in VLBI analysis. The other auxiliary parameter groups, zenith wet delays (ZWD) and clocks, are only relatively constrained, i.e. their temporal variations are restricted to stay within predefined limits. Due to the direct constraint, precise VLBI solutions depend on the exact knowledge and application of a priori gradients. Our study concentrates on the optimal size of the constraints and the interval lenghts of the various auxiliary parameter groups depending on the network, i.e. the type of session, or the time of the session, e.g. the year. The impact of the different size of the constraints and the interval length for ZWD, clock and gradients on various VLBI solutions analysed with the Vienna VLBI Software (VieVS) is assessed by descriptive statistics.