The results presented in this paper concern investigation of environmental influences to GNNS coordinates on the example of ASG-EUPOS network. The problem of the impact of environmental effects is crucial for observing gravity. Satellite systems are not as susceptible to changes in local hydrology or atmospheric effects, although significant influences are clearly visible in the change of coordinates. The authors analyzed daily and sub-daily solutions (geocentric coordinates) in the context of different disturbances to eliminate sites suffering from poor quality for further researches (e.g. data from the most reliable ASG-EUPOS stations will be used for investigating the correlation of their movements with the lithosphere deformations on territory of Poland). There are many doubts regarding proper antennas’ placement - as they are mostly placed on the roofs, there were questions if data from these sites can be used for scientific purposes like velocity estimations or geodynamical researches. Analysis of daily solutions was supposed to prove that the majority of Polish sites give fully valuable data. Some factors that may cause a precision decreasing can be avoided or eliminated in the future. Taking into consideration that GLONASS will be soon fully operational and it will be an alternative for commonly used GPS, the authors made separate elaboration of GPS and GLONASS data. Usage of two different satellite systems holds the potential to increase of solutions’ reliability and eliminate errors that could be possibly related to the specific satellite system. Base on time series of coordinates residual values, systematic errors that could prove geophysical and geodynamical influence on GNSS measurements were investigated. In this elaboration only post-processing observations were taken into account, but the monitoring of the network in the near real-time by means of coordinates’ stability is under development., Janusz Bogusz, Mariusz Figurski, Krzysztof Kroszczyński and Karolina Szafranek., and Obsahuje bibliografii