Khoptar A. Troposphere tomography based on the data processing of multi-GNSS observations

In recent years, the scientific application of Global Navigation Satellite Systems (GNSS) in the Earth sciences has gained important status and role. With modernization of the American GPS (Global Positioning System), restoration of the Russian GLONASS (GLObal'naja NAvigacionnaja Sputnikovaja Sistema), as well as new constellations of navigation satellites, such as the European Galileo system and the Chinese BDS system (BeiDou Navigation Satellite System) in formation of GNSS have been radical changes in the field of multifrequency constellations - multi-GNSS, which brings great opportunities for both scientific and technical applications, as a significant mprovement in satellite visibility, spatial geometry, increases the accuracy and reliability of satellite measurements based on multi-GNSS observation data. With the rapid development of GNSS, the Precise Point Positioning (PPP) is also moving forward. The main prospect of application of this method is the autonomy of determining the spatial position of points. At the present stage of science development there are a number of problems that are at the intersection of different areas. One of such problem, the solution of which is possible with the use of GNSS-technologies, is the study of water vapor content in the Earth's troposphere, which plays a significant role in many atmospheric processes. Thus, the main attention of this dissertation is focused on conducting research of expanding the methodological possibilities of reconstructing the vertical profile of water vapor content in the Earth's troposphere based on the processing of multi-GNSS observations by the PPP method.