Unmodelled Effects in the Horizontal Velocity Field Determination: ASG-EUPOS Case Study

Recent space and satellite technologies offer great opportunities to determine crustal movements in the single, global reference frame. The densification of the global network through local area networks leads to increase the resolution of modelled deformations both horizontal and vertical. However, the credibility of the obtained velocity field is limited by several factors associated with unmodelled (or mismodelled) effects at the stage of GNSS data adjustment. Some of them are periodic (the influence of local atmospheric or hydrological impacts), some temporary (natural or anthropogenic seismicity) or related to local influences (snow load or effects associated with the freezing of the ground). This paper presents the usefulness of ASG-EUPOS time series for determination of the regional velocity field. The system has been operating since mid-2008, so the velocities obtained through the processing of 3-year time series are supposed to be reliable. The paper also presents comparison of the velocity determinations to the geological NNR-NUVEL-1A and geodetic APKIM2005 models.