Towards an IAG combined global GNSS velocity field

GNSS velocities estimated by different analysts can significantly differ due to the choices made concerning the GNSS data processing (corrections applied and noise level of the series), the completeness of the series, the removed position discontinuities and the alignment to a terrestrial reference frame. The position discontinuities that populate the GNSS time series have probably the biggest impact on the error or dispersion of the velocity estimates at the same sites. Even when using exactly the same position series, different analysts may provide different velocity estimates and uncertainties mainly due to the choice of removing different position discontinuities.

The IAG Joint Working Group 3.2 (2019 – 2023) aims at providing a global combined GNSS velocity field that takes into account the repeatability, the alignment and the relative weighting of the velocity estimates by different groups. We expect that this IAG’s unified GNSS velocity field will be useful for the scientific community inside, but especially outside, the geodetic community in areas such as tectonics, sea-level change and GIA modeling among others.

In this contribution, we present the current status of the global combined velocity field, aligned to the recently released ITRF2020, and based on the velocity fields provided by several other groups.