The results of the determined ionization identifier TEC (Total Electron Content) for continuously operating reference Global Navigation Satellite Systems (GNSS) stations are analysed. On the one hand, the data reflect the state of the ionosphere during the observation; on the other hand, it is a substantial tool for accuracy improvement and reliable determination of coordinates of the observation place. It was decided to solve a problem of restoring the spatial position of the ionospheric state or its ionization field according to the regular definitions of the TEC identifier, i.e. VTEC (Vertical TEC). We have described one possible way of solving this problem, which is based on mathematical modelling by using degree polynomials and trigonometric Fourier series. Degree polynomials describe the trend of function, whereas the trigonometric Fourier series are used in order to better simulate the fluctuation. The method was tested for network of permanent stations ZAKPOS.

According to the fast development and distribution of GNSS technologies all over the world, the large numbers of reference GNSS stations have appeared in Ukraine. These stations are included in the state and several private networks. The permanent GNSS observations gathered within these networks are processed and analysed by the Centre of Lviv Polytechnic National University. A cumulative solution (coordinates expressed at the specified epoch and velocities of all stations) was estimated by using the GAMIT-GLOBK software. The authors made several numerous tests using certain configuration of fiducial stations which belong to the EPN A class to transfer ITRF08 frame into Ukraine area and choose the best strategy of alignment of the Ukrainian national GNSS network to the EPN. Three different solutions with cretin tolerance set for Ukrainian GNSS network were estimated and each time the different set of coordinates was obtained. The differences reached several millimetres. Also for verification, our solution was compared with EPN solution. Received coordinates and velocities could have a geophysical interpretation and provide very useful information for local geodesy tasks.