INTERGEO Agenda - english

Observations of permanent Global Navigation Satellite Systems (GNSS) station positions contain signals of displacements of the Earth’s crust, caused by mass variations in the atmosphere, ocean and local hydrology. Models of such Non-Tidal Loading (NTL) displacements, based on a variety of geophysical data and modeling choices, are readily available, but these effects are not generally applied in the realization of the International Terrestrial Reference System (ITRS). In the last years, additional models of the NTL were published and established ones updated. With that, a variety of modeled NTL signal representations with different strengths and weaknesses exist. Bringing the theory of NTL effects and GNSS station position time series together enables the correction of GNSS data for these effects, resulting in more stable and reliable station positions. Vice versa, the dense, global network of GNSS stations helps in the validation of the modeled displacements. Together, these applications support the exploration of geophysical processes in detail. In this study, we employ a high accuracy processing of raw GNSS observations of globally distributed stations, yielding a consistent network estimate to study the NTL effects in detail. Time series of solutions generated with and without the correction for NTL displacements, taken from different models, allow for in-depth analysis between them. Autoregressive processes from these time series data gives reliable covariance information, which form the basis for the application of statistical testing methods. Here, we test for significant changes in various parameters between multiple realizations and quantify the differences, aiming to investigate strengths and weaknesses of different NTL models.