Impact of Coordinate- and Tropospheric Ties on the Rigorous Combination of GNSS and VLBI

Abstract

AbstractIn this work, we study the impact of the use of site coordinate and tropospheric ties between VLBI telescopes and GNSS antennas at co-location sites during the CONT17 campaign. We perform the rigorous estimation of all parameter types common to these two techniques: station coordinates, troposphere zenith delays and gradients, and the full set of Earth Orientation Parameters (EOPs) and their rates, including their full variance-covariance information. The core element of our processing scheme is the combination of the techniques via coordinate and tropospheric ties, the later being essential especially for the height estimates. By using and evaluating different weighting schemes, to obtain a unique set of consistent parameters, we analyse coordinate repeatabilities and the behaviour of the EOPs, to discuss the impact of the accuracy and weighting of the coordinate and troposphere ties on the estimation of geodetic parameters. Our work shows that the combined solution with coordinate and troposphere ties generally improves the precision of all the estimated geodetic parameters. In particular, the repeatabilities of the height component, the polar motion estimates, and the LOD, show improvements up to 19%, 35% and 48%, respectively, with respect to the single-technique solutions. These results provide enough evidence of the benefits of our approach.