In the diploma thesis we analysed the quality of GNSS observations when using various antennas. We tested an internal antenna, installed into a Javad Triumph-LS housing, an external antenna and the choke ring antenna, which is the least sensitive to the reflection of signals from objects. After the survey and quality assessment of GNSS observations in programs TEQC and Leica SPIDER QC we confirmed the presupposed hypothesis that the choke ring antenna provides us best observations. In second part we checked whether the coverage of the metal barriers with white sheet or wooden panel reduces signal reflection from obstacles. We concluded that the signal mostly reflects by the metal. At the same time, we also tried to explore other factors affecting multipath size. Mostly, it is necessary to pay attention to the elevation angles and geometry of the satellites. GNSS observations were performed with static method and postprocessed in program package Leica Geo Office, where we determined the positions of points A and B in two modes: virtual reference station (VRS) and permanent station. This way, the influence of distance to reference point on quality position was tested. We concluded that the deviations were of milimeter magnitude in horizontal and of centimeter magnitude in vertical direction.