The main goal of our research was to estimate the accuracy regional combined GNSS solution by changing the duration of observations and configuration of the reference stations network. Methods. As the initial date for investigation were the results of 4 weeks from 119 reference stations in Ukraine. These results of observation were used for design four networks with different sets of reference stations and for each network was calculated the combined solutions. The estimation of the combined solution was performed by program GAMIT/GLOBK, changing parameters such as the duration of observation (3 days, 1, 2, 3, 4 weeks) and the transformation parameters (linear and angular). One network with 24 reference stations and the appropriate solution we took as real position of stations and compared it with the solutions obtained from the first network where the number of reference stations is 6, the second network where the number of reference stations is 18 and third is 14 reference stations. Also from EPN Analysis Combination Centre we took the stations coordinates for investigation requirement angular parameters of transformation. By comparing the real coordinate and coordinate determined in our combined solution we compute RMS of the positioning. Results. The RMS analysis revealed that in creating a combined regional solutions when imposing minimal constraint metod appropriate to use in addition to the linear transformation parameters also angular. Also used as the fiducial stations of the highest class, which are uniformly located in Ukraine and abroad, and completely cover the country. Scientific novelty and practical significance. Opportunities for regional solutions combined using a small time period of observations from three days to four weeks (monthly), is not investigation today. The survey results make it possible to set the best time for observing national networks as well as the optimal network configuration settings and necessary transformation in regional combined solutions.
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