The Correlations of the Helmert Transformation Parameters as an Additional Auxiliary Diagnostic Tool for Terrestrial Reference Frames Quality Assessment

AbstractIn the present study, we estimate the correlations of the Helmert transformation’s parameters for various Terrestrial Reference Frame realizations (TRFs). The correlations can be served as an auxiliary diagnostic tool on assessing the quality of the Helmert transformation parameters (origin, scale, orientation and associated rates, respectively). Possible high correlations between the pair of parameters are signs of strong dependency of each other, hence their estimation can lead to misinterpretations. We compute the Helmert correlation coefficients of global TRFs for the following cases: (a) the SLR and VLBI intra-technique combinations contributing to the DTRF2014 construction and the associated SLR and VLBI inter-technique combinations and (b) the DORIS-related TRFs computed by the International DORIS Service (IDS) and the ITRF2014 (International TRF 2014). The results verify the good quality of DTRF2014 (DGFI-TUM TRF 2014) in terms of the Helmert parameters quality, for both SLR- and VLBI-related TRFs. For the case of the DORIS solutions, we find that the correlations are severely increased for the solution that includes 5 more years of observations than the ITRF2014 one.