In this thesis we dealt with the quality of data and products provided by the national GNSS network SIGNAL. The tests were carried out at three sites comprising a virtual grid of points with generated observations in the form of a VRS, a site on Krvavec and a site in the Avtosejem area in Ljubljana. We tested different influences on observations and the quality of point coordinates. We were interested in the influence of the length of the base vector, the height difference between the base point and the rover, the duration of the observations and the direction of the base vector between the base and the new point. We were additionally interested in the influence of the elevation of the site and the altitude of the VRS. At the Krvavec and Avtosejem work sites we also analyzed the quality of the relative coordinates between the points.