Correcting Non-Tidal Surface Loading in GNSS repro3 and Comparison with ITRF2020

Time-dependent mass variations lead to significant and systematic load-induced deformations of the Earth’s crust, impacting space geodetic techniques. Using the ESMGFZ loading models, the impact on the recent IGS reprocessing campaign (repro3) is studied. While non-tidal loading was not corrected in the original repro3, separate solutions were computed by applying the corrections at the solution and the observation level. An initial comparison between the seasonal components in the loading models revealed a good agreement with the periodic functions in the ITRF2020. Based on the considered test period (2012–2016), we found reduced statistical signatures if applying the corrections at the solution level. For the annual amplitudes in the Up direction, an overall reduction of 18% was achieved. Correcting at the observation level provided larger reductions (amplitudes are reduced on average by 42%). Moreover, the consistency of the derived products, i.e., satellite orbits, Earth rotation parameters, and station coordinates, is achieved. Overall, it is recommended to correct non-tidal loading displacements primarily at the observation level. In case of technical restrictions or software limitations, corrections should be applied at the solution level.