Purpose. Solutions to the problems of coordinate-time provision based on continuous GNSS-observations is based on the processing of large data sets of code and phase measurements. One of the possible additional options for conducting this study is computation of the numerical characteristics of the ionospheric impact on the signals distribution from the satellites – the values of the total electron density (TEC). These characteristics reflect the dynamics of the atmosphere ionization that is important in terms of monitoring the circumterrestrial space. Arrays of the STEC and VTEC values are so significant that there is actual problem of preparing ionosphere parameters for their further analysis and use. To solve this problem, we proposed a technique based on a set of programs that convert VTEC data measurements to a format suitable for the analysis. Methods. TEC indicators can be computed due to the automated processing of files with GNSS-observation results from each satellite for an individual station. Processing algorithm is based on the use of the computed code and phase pseudo-distances in the receiver and calibration coefficients. This algorithm allows you to get the TEC values in two ways: a) according to the phase measurements only and having used the results of phase ambiguities in the network as a whole beforehand and b) according to the code measurements only that were smoothed beforehand. In one-station algorithm, TEC value is determined for an individual station according to the measurements of all satellites during the period of 24 hours. For converting STEC (along the satellite-receiver beam) in vertical VTEC, a vertical single-layer model of the ionosphere is used. This model presupposes that all the electrons are concentrated in a thin layer that is located at a certain height above the Earth's surface. Results. For determination of the spatial TEC distribution, an algorithm of processing GPS measurements for multiple-stations was implemented using a network of active reference stations in the Western Ukraine. The network consists of 17 stations that work under control of specialized software in real time to provide the RTK services to the wide range of users interested in geodetic areas. Scientific novelty. The program for calculation of the STEC and VTEC values was written. This program uses already known subprograms, that are used for reading RINEX files, detection, estimation, and elimination of cyclical phase jumps, which arise in the process of measurements, subprograms that we developed for smoothing code measurements, receiving differential corrections at the time, calculation of the horizontal coordinates of the satellite on the observational station, direct calculation of TEC and subsequent storage of the received data in the new file on the server of Lviv Polytechnic National University. The entire program was compiled for the Linux operating system and automated for use with observational data of permanent IGS station SULP. The research resulted in improvement of an algorithm for determining the parameters of the ionosphere, development and implementation of software for regular computing of the ionospheric parameters – slant (STEC) and vertical (VTEC) values of total electron content, and proving of its practical use on SULP station. Practical significance. Calculation of the parametres of ionosphere at fixed moments of observation for each GNSS- satellite.
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