K. Kaniuth Crustal deformations in the Central Mediterranean derived from the WHAT A CAT GPS project ABSTRACT The West Hellenic Arc Tectonics And Calabrian Arc Tectonics (WHAT A CAT) project aimes at monitoring crustal deformations in the Central Mediterranean by repeated GPS campaigns. The data set acquired so far is rather heterogeneous in terms of availability of GPS satellites, performance of the involved receiver systems and quality of the satellites' orbits. The paper presents the velocity estimates achieved using a modified version of the Bernese GPS software. Main characteristic of the solution strategy is the definition of station velocity parameters already on the observation equation level. ----------------------------------------------------------------------- In Proceedings of the 13th Working Meeting on European VLBI for Geodesy and Astrometry, Viechtach, 1999 Keywords: GPS, Crustal deformation, Mediterranean Sea, GPS processing