This session has two closely related aspects. One goal is to provide a forum to discuss preparations for the next International Terrestrial Reference Frame (ITRF), as well as its usage and applications in Earth science applications. Participants can discuss concerns of not only related to the contributing technique services, but also all ITRF uses, ranging from local, regional to global applications. Contributions are sought from the individual technique services and various ITRF users, covering the complete range of topics, such as data analysis, parameter estimation, correction models, and focusing especially on identifying and mitigating systematic errors, which will hopefully help improve the next ITRF solutions.

The second part of this session examines progress in the 12 years since the IERS campaign to study geocenter motions. There have been large strides in observational results from space geodesy during that time, as well as better theoretical developments. The effects of large-scale motions of the solid Earth with respect to the total planetary center of mass, while small, are much better understood now and their significance is widely appreciated for a range of geophysical modeling. This session aims to try to summarize the current state of understanding, observationally and theoretically, and to focus on areas of remaining uncertainty.