Continuous monitoring of artificial space objects needs periodical control of quality of observational data. Estimation of internal accuracy allows to control and exclude outliers in the array of primary data. For artificial satellites it is also possible to compare orbital elements calculated by Research Institute “Mykolaiv Astronomical Observatory” (RI MAO) with precise data which provided by International Laser-Ranging Service (ILRS) or Global Navigation Satellite System (GNSS). Such comparison allows to detect problems with time synchronization, reveal and estimate systematic errors etc. RI MAO carries out regular observations of artificial satellites in different orbits using several telescopes and forms catalog of their orbital elements in TLE format during more than 10 years. Software for orbital elements calculation was developed in collaboration with Astronomical observatory of Odessa National university. This paper presents an analysis of the processing results of the observational array of 149 geostationary satellites (GSS). Observations were performed using RI MAO Telescope Complex during 2020...2021. Time synchronization is provided with GPS Resolution-T receiver with RMS = 40 ns. All GSS observations were carried out using the combined method developed at the RI MAO. A total of 134461 positions were received for which residual (O – C) differences were calculated with respect to the computed orbit. The mean square error of observations of the GSS in the apparent magnitude range 9_m...13_m was 0.5" in right ascension and declination. Computed orbital elements were compared with precise ILRS data. Comparison of the orbital positions of the GSS, calculated from the RI MAO orbital elements with the ILRS data showed that the differences between the corresponding geocentric сartesian coordinates were dX = 0.72 km, dY = –0.52 km and dZ = 1.28 km at the start of the forecast.