Observation Level Combination of GNSS and VLBI with VieVS: a simulation based on CONT11

GNSS and VLBI antennas were connected to the identical hydrogen maser clocks at seven sites during CONT11, which means that clock parameters can be regarded as common parameters at those sites as well as troposphere parameters. We construct GNSS single differences between the ranges from two stations to a satellite, using corrected phase measurements with the c5++ software. Combining GNSS single difference and VLBI data during CONT11, we estimate station coordinates and site common parameters, i.e. zenith wet delays, troposphere gradients and clock parameters, with the Vienna VLBI Software (VieVS). Local tie vectors, which contribute to the combination of terrestrial frames between GNSS and VLBI, are introduced as fictitious observations. We compare combination solutions with single technique solutions, assess the impact of the combination at the observation level with respect to geodetic results and discuss the current limitation and potentials to be developed