EPN Data and Product Analysis for Improved Velocity Estimation: First Results

The EUREF Permanent Network (EPN), established in 1996, consists currently of more than 120 GPS stations from 30 European countries. A significant portion of the network has more than 3 years of observation history, which provides the potential for reliable velocity estimation relevant for geophysical interpretation.This paper addresses the main error sources degrading the quality of the velocity estimation, illustrated with examples taken from the EPN. At the observation level, we demonstrate that changes in the station equipment and tracking performance can cause discontinuities and non-periodic signals, while monumentation commonly introduces annual signals in the coordinate time series. In addition, the RMS of the estimated coordinates and velocities can also be increased. At the processing level we demonstrate the importance of the appropriate reference frame fixing to avoid systematic biases in the estimated velocities.The derived residual (intraplate) velocities confirm the stability of the EPN at the level of a few mm/year. Velocities contradictory to the tectonic expectations are found only for stations with short observation history.