GNSS application for positioning, navigation and timing is increasing every year. Ground based DGNSS augmentation system EUPOS® has been developed in Central and Eastern European countries during last 7 years with a dense coverage of continuously operating reference station networks. Currently EUPOS® created RTCM corrections mainly used by land surveyors, cartographers and geodesists. However, recently more applications appears in agriculture and road construction for machine guiding (Horváth, T., 2008, Muhr, T., 2008), for precise maritime navigation in harbors (Oltmann, J.-H., Hoppe, M., 2008) and the first attempts for aviation (Zaki, G., 2008). Many of EUPOS® antennas have been individually calibrated. Three solutions were made with Bernese GPS Software V5.0: Nordic, Mid-Europe and EUPOS. Antenna calibration effect is discussed in this paper. It appears that absolute calibration effect can cause the coordinate difference up to 6 cm in geodetic network solution. It is important to individually calibrate GNSS antennas in order to achieve higher precision. Similarly in geodetic network solutions the network effect can cause some coordinate shift as a result. Comparing the Nordic solution with Mid-Europe solution the coordinate difference is up to 3.5 mm and comparing EUPOS solution with Nordic solution and Mid-Europe solution the coordinate difference is up to 12.5 mm. In case of geophysical research or in case of geodetic reference network catalog creation such an error is meaningful.