Determination of reference directions at a certified range using GNSS measurements

The relevance of PPP technology has greatly increased over the past 10 years. While the centimeter level of accuracy has already been practically ensured in most spheres of economic activity, first of all, in geodesy, the millimeter level for scientific tasks related to the study of the influence of geophysical factors on the environment is still the subject of research. The purpose of this work is to identify the real accuracy of the modification of the PPP-AR method using the example of data from four permanent GNSS stations: SULP (Lviv), FRAN (Ivano-Frankivsk), RAHI (Rakhiv), TERN (Ternopil), included in the European the EPN network (EUREF Permanent GNSS Network). Method. To fulfill the given task, we used data from four permanent GNSS stations. 3 weeks of observations were processed: one in July (2217 GPS week), one in August (2222 GPS week) and one in September (2226 GPS week). Processing of the observation files was carried out in the PRIDE PPP-AR software environment, which was pre-installed on the server with the Ubuntu operating system. The coordinates of each station were calculated with the same input parameters, namely, taking into account the second-order ionospheric correction and the function of displaying inclined zenith delays of signals from satellites in the direction of the VMF3 zenith. We compared the obtained sets of coordinates with the control coordinates of these stations. For the time periods we chose, the coordinates calculated by the relative method based on the formation of phase differences in the combined EPN processing center were taken as control. The results. The main results of our research were the difference of coordinates (comparison of the received coordinates with control ones). For each station, the obtained differences are unidirectional in nature and vary little between stations. The average value of the coordinate differences was from 0.6 to 7.2 mm and practically does not depend on the processing time interval. The root mean square error (RMS) of the coordinate differences is at the level of 1.5 – 3 mm and also changes little over time. It was found that the accuracy of determining the coordinates based on the processing of GNSS measurement data at permanent stations SULP, TERN, FRAN, RAHI using the PPP-AR method is quite high, but a systematic difference of several millimeters is noticeable, which may be caused by insufficient consideration of some factors of geophysical origin . Scientific novelty and practical significance. It is shown that the PPP-AR method at the current stage of development of GNSS technologies achieves the accuracy of the coordinate determination method based on phase differences and can be applied not only in geodesy tasks, but also in geodynamic studies, provided the results of daily GNSS observations are used. A promising direction for further research is the identification of unaccounted sources of systematic errors.