Position, velocity and time measurement with multiple constellation data from GPS, GALILEO, GLONASS and BEIDOU

This work intends to outline the theory and the methods for the computation of position, velocity and time (PVT) of a user on the surface of the Earth or of a LEO satellite (Low Earth Orbit). An integrated software written in MATLAB and PERL has been used; it processes all the signals transmitted by all the constellations visible in that precise moment and in that precise place. The software's core uses the Weighted Least Squares algorithm, which permits the efficient computation of position, speed, timing and tropospheric delay in a few iterations. In this thesis, signals from GPS, Galileo, BeiDou and GLONASS have been used, specifically for the computation of the speed, which is calculated from the Doppler Effect. These signals were detected through a receiver STONEX Cube-a S580 provided by the University of Padua. A good precision in determination of both positioning and speed has been achieved and also the PNT of a LEO satellite (Sentinel 3A) has been determined successfully, using data also to study J2 perturbations on the orbit. The principal aim of this thesis is to provide an efficient and precise software able to process pseudorange and Doppler shift multi-constellation data, to enhance, in its future evolutions, the precise positioning of a receiver on Earth's surface and in orbit, with interesting applications in many different fields such as defence, transportations and automotive, attitude determination in space and many others.

Il presente lavoro si propone di illustrare la teoria, il metodo e le modalità del calcolo della PVT, ovvero della posizione, della velocità e del sincronismo temporale, di un utente sulla Terra o di un satellite in orbita bassa (dotato di ricevitore multiGNSS), utilizzando un software integrato che sfrutti tutti i segnali provenienti da tutte le costellazioni a copertura globale in quel momento visibili. Nel caso presente si sono utilizzati i segnali da GPS, Galileo, GLONASS e BeiDou, rilevati grazie ad un ricevitore fornito dall'Università di Padova (STONEX S580), sia per la determinazione della posizione, sia per implementare il calcolo della velocità attraverso l'effetto Doppler. Questo lavoro, in futuro, potrebbe portare a contributi nello sviluppo di tecnologie innovative in molti settori, quali: navigazione autonoma e trasporti, difesa e aerospazio, agricoltura e molti altri.