A reliability of site movement assessments determined from GPS data monitored during eight two-day epoch measurements on the regional geodynamic EAST SUDETEN network (the Bohemian Massif, Central Europe) is discussed in details. Statistical tests of site positions processed by the BERNESE GPS software, their linear approximations for site movement velocity assessments and an establishment of probabilistic thresholds for reliability of the GPS data for regional geodynamic studies are delivered. The thresholds define necessary observation periods for annual epoch measurements performed on the networks with aim to obtain reliable movement estimates for geodynamic studies., Vladimír Schenk, Zdeňka Schenková, Jaroslaw Bosy and Bernard Kontny., and Obsahuje bibliografii