The International Terrestrial Reference Frame: lessons from ITRF2014

Abstract

We review the progress and continuous improvements being made since more than 30 years in the determination and development of the International Terrestrial Reference Frame (ITRF). We present the modeling innovations introduced in the ITRF2014 elaboration, mainly (1) the estimation of the annual and semi-annual signals embedded in the time series of station coordinates provided by the four space geodesy techniques, and (2) the incorporation of post-seismic deformation (PSD) models for sites subject to major earthquakes. We recall the rank deficiency problem in the ITRF combination model that is related to the specification of the ITRF defining parameters. We evaluate the precision and accuracy of the main ITRF2014 geodetic and geophysical products using some key performance indicators. We address some scientific questions of space geodesy contribution, via ITRF2014 results, to understand geophysical processes that affect the Earth system, such as earthquake displacements, tectonic motions and loading effects. We evaluate in particular the performance of estimating periodic signals versus applying a non-tidal atmospheric loading model. A particular emphasis is devoted to the level of agreement between techniques in terms of seasonal signals, frame physical parameters (origin and scale) and consistency with terrestrial local ties at co-location sites. Main conclusions are then drawn to guide and improve our analysis and combination strategy for future ITRF developments.