The Assessment of the Temporal Evolution of Space Geodetic Terrestrial Reference Frames

Abstract

The assessment of the accuracy and the stability of the global Terrestrial Reference Frames (TRFs) is a matter of great importance for the geodetic community. The classical Helmert transformation plays a crucial role in terms of evaluating the datum related parameters of global TRFs (origin, scale, and orientation, and their associated rates). We discuss a new alternative approach for the assessment of TRFs temporal evolution and we compare it with the Helmert transformation. Our concept relies on the splitting of the velocities into two specified parts. The first one is referred to the reference system effect and the latter one to the deformation, respectively. This separation is done in order to create the necessary mathematical tools for the TRF assessment. The new approach is tested on the single-technique TRFs (VLBI, SLR, GPS and DORIS, respectively) of the DTRF2008. The novelty of the new methodology is its ability to treat individually the systematic errors of each TRF. This feature detects systematic effects that the Helmert transformation cannot. The results reveal that the new approach and the Helmert transformation show almost the same results in terms of rates of the datum parameters with an uncertainty of 0.1–0.3 mm/year for the four space geodetic techniques TRFs. The uncertainty refers to the estimated rate differences standard deviation between the new approach and the Helmert one.