Impact of alignment strategy to the reference frame on the 3D annual station motions from different GNSS solutions

Abstract A comparison of the three-dimensional annual motions of the global Navigation satellite system (GNSS) stations in two different solutions – the latest reprocessing campaign of the International GNSS Service (IGS), and the station position time series provided by the Nevada Geodetic Laboratory (NGL) – reveals large-scale differences with amplitudes of about 1 mm in horizontal and 3 mm in vertical. We show that these differences are largely explained, in the vertical component, by differences between the alignment strategies of both solutions to the terrestrial reference frame. Further comparisons with the annual displacements predicted by a global loading deformation model suggest that true annual station motions are less subject to aliasing, hence better preserved with the IGS alignment strategy. Considering these results, we urge providers of GNSS station position time series to take measures to minimize the aliasing of geophysical station motions that occur when aligning their daily station position estimates to the reference frame and propose different such measures.