Doprinos određivanju jonosferskog kašnjenja GNSS satelitskih signala na teritoriji Republike Srbije

Abstract

Višefrekvencijski GNSS satelitski signali i njihova dostupnost omogućavaju istraživanja u nediferenciranom i nekombinovanom modelu u kome je pojedinačni signal na svakoj frekvenciji odgovarajuće nezavisno opažanje. Ovakve mogućnosti izazivaju veliko interesovanje ne samo u geodetskim istraživanjima već i u mnogim oblastima primene GNSS opažanja. Na geometrijskoj putanji signala između satelita i prijemnika, značajni izvor grešaka GNSS merenja dolazi zbog sredine prostiranja elektromagnetskih talasa. Greške koje se pripisuju prostiranju signala su jonosferski i troposferski uticaji. Navedeni izvori grešaka značajno utiču na kvalitet određenih pseudodužina, pa samim time i na kvalitet određenog položaja prijemnika u vidu trodimenzionalnih koordinata. U radu je prikazana analiza i određivanje jonosferskog kašnjenja GNSS satelitskih signala na osnovu određivanja Total Electron Content – TEC na pet stanica (Beograd, Leskovac, Sombor, Zaječar i Kraljevo) na prostoru Republike Srbije. U cilju određivanja vrednosti TEC-a, korišćen je softver pod nazivom „GPS-TEC analysis“ razvijen u okviru Institute for Scientific Research, Boston College, USA, koji omogućava određivanje TEC vrednosti na putanji između satelita i prijemnika. Prikupljanje podataka izvršeno je u okviru 2022. godine tako da merne sesije obuhvate karakteristične datume u okviru godine kada se očekuju najveća kolebanja u kontekstu sezonskih varijacija.

Multi-frequency GNSS satellite signals and their availability enable research in undifferentiated and uncombined models in which a single signal at each frequency is a corresponding independent observation. Such possibilities are reflected by the significant interest in geodetic research as well as in many areas of application of GNSS observation. On the geometric path of the signal between the satellite and the receiver, a significant source of GNSS measurement errors comes from the medium of propagation of electromagnetic waves. Errors attributed to signal propagation are ionospheric and tropospheric signal delay. The mentioned error sources significantly affect the quality of certain pseudorange and, thus, the quality of the receiver's position in the form of three-dimensional coordinates. This paper presents the analysis and determination of the ionospheric delay of GNSS satellite signals based on the determination of Total Electron Content - TEC at five stations (Beograd, Leskovac, Sombor, Zaječar, and Kraljevo) in the territory of the Republic of Serbia. In order to determine TEC values, the software called "GPS-TEC analysis" developed within the Institute for Scientific Research, Boston College, USA was used, which enables the determination of the TEC value on the path between the satellite and the receiver. The data collection was carried out within the year 2022 so that the measurement sessions include characteristic dates when the most significant fluctuations are expected in the context of seasonal variations.