With new satellites of different Global Navigation Satellite Systems being launch every year in order to improve global positioning coverage, GNSS positioning is becoming a more and more used technique for various applications where position is needed. One of its abilities is to provide high accuracy and high precision coordinates in real time with a very high positioning rate of 1 Hz or even 10 Hz. This is a very desired condition in monitoring projects, thus GNSS monitoring is becoming used more often in continuous monitoring applications.
GNSS monitoring is usually done by applying differential GNSS techniques. Therefore, the purpose of this research was to evaluate and compare long term differential GNSS real time positioning results obtained by using different GNSS and frequency combinations. Single- and dual frequency real time positioning of two, 51 and 13990 metre long baselines were computed several times using 14 day GNSS data sets from three GNSS receivers. These data sets included observations of GPS, GLONASS and BeiDou navigation satellite systems, which resulted in seven different GNSS combinations. Real time positioning coordinate series of all combinations between seven GNSS combinations, two frequencies and two baseline lengths were then analysed and compared to one another. The thesis ends with discussion about the results of this analysis, which are presented through various plots, histograms and statistical indicators. Findings show differences in results when using each GNSS separately or in different combinations. As a standalone system GPS proved to be the most accurate, while the combination of all three GNSS gave the best numerical results.