POINT POSITION ACCURACY IN A VECTOR GNSS NETWORK AND THE WAY IT IS LINKED TO REFERENCE STATIONS

The aim of this study is to assess the impact of the location (distribution) of reference points (reference stations of the ASG-EUPOS system) on the accuracy of the final determination of the local measurement grid points. The research was carried out in terms of the possibility of using the static GNSS method to determine displacements, both relative (vector lengths) and absolute (coordinates in the spatial system). A mathematical record of the computational process (functional model and stochastic model) was presented, on the basis of which the test vector network was adjusted (indirect method) and the accuracy assessment after the adjustment was performed. The subject of the numerical tests were the actual measurement results of a part of the geodetic network (GNSS vectors) established in the mining area (the results of one of the periodic measurement cycles were used). Numerical analyses take into account several different variants of establishing the network: depending on the location (direction east–west, north–south) and the number of ASG-EUPOS stations used. The following parameters (relating to the designated positions) were adopted as comparative criteria: coordinate deviation (in the Cartesian geocentric system) from the reference values, spatial length deviation between the designated points from its reference value, mean coordinate errors, error in the position of a point in three-dimensional space, length mean error as a function of adjusted observations (using the law of transfer of errors of mean correlated quantities). Particular attention was paid to the discrepancy between the adjustment results for different systems of reference to the ASG-EUPOS stations. On the basis of the performed calculation tests and the performed comparative analyses, conclusions were compiled that may be helpful in planning periodic measurements for the purpose of determining land displacements.