Dissertation Ionosphere

Dissertation Ionosphere-22
As the performances of the PPP algorithm rely on the precision of carrier phase measurements, the PPP algorithm is more sensitive to ionospheric scintillations than the SPP algorithm, which is based on code pseudorange measurements exclusively.In case of active ionospheric scintillation conditions, the Root-Mean-Square Error (RMSE) of the tridimensional PPP solution can be as high as 6.73 m and its success rate as low as 50% by comparison to 0.18 m and about 100%, respectively, during quiescent conditions.First, this Ph D thesis presents a statistical analysis based on measurements performed by a network of Ionospheric Scintillation Monitoring Receivers (ISMRs) located near the magnetic equator in Brazil and collected during the year 2014, i.e.

As the performances of the PPP algorithm rely on the precision of carrier phase measurements, the PPP algorithm is more sensitive to ionospheric scintillations than the SPP algorithm, which is based on code pseudorange measurements exclusively.In case of active ionospheric scintillation conditions, the Root-Mean-Square Error (RMSE) of the tridimensional PPP solution can be as high as 6.73 m and its success rate as low as 50% by comparison to 0.18 m and about 100%, respectively, during quiescent conditions.First, this Ph D thesis presents a statistical analysis based on measurements performed by a network of Ionospheric Scintillation Monitoring Receivers (ISMRs) located near the magnetic equator in Brazil and collected during the year 2014, i.e.

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The spatial analysis techniques exploited in the framework of this research eventually led to the design of three types of real-time ionospheric scintillation skymaps that quantify the spatiotemporal characteristics of low-latitude ionospheric scintillations.Best performances for the SPP and PPP algorithms in terms of reliability are obtained by hybrid strategies targeting both the stochastic modelling and the integrity monitoring stages of the algorithms.Les systèmes globaux de positionnement et de navigation par satellites (Global Navigation Satellite Systems – GNSSs) occupent désormais une place prépondérante dans notre société moderne.Finally, this Ph D thesis describes the design and benchmarks the performances of several categories of prototype mitigation strategies against ionospheric scintillations that target the stochastic modelling and the integrity monitoring stages of the SPP and PPP algorithms.The design of the strategies is based on several types of ionospheric scintillation skymaps and the benchmark of their performances relies on the definition of several specific performance parameters.In particular, small-scale irregularities and inhomogeneities in the ionospheric free-electron density are responsible for diffraction and scattering effects on GNSS signals that propagate through such ionospheric disturbances.These effects result in rapid fluctuations of the amplitude and phase of GNSS signals, also known as ionospheric scintillations, which can severely disrupt the performances of GNSS navigation and positioning algorithms.L’objectif ultime poursuivi par cette Thèse de Doctorat consiste à développer des prototypes de stratégies d’atténuation des effets des scintillations ionosphériques afin d’améliorer les performances des systèmes de positionnement par satellites en cas de scintillations ionosphériques équatoriales.En particulier, cette recherche cible deux algorithmes de positionnement par satellites, à savoir le Standard Point Positioning (SPP) et le Precise Point Positioning (PPP).Strategies related to the weighting scheme of the stochastic model provide better results for the SPP algorithm than the PPP algorithm whose performances are further enhanced by strategies implementing spatial masks.Prototype mitigation strategies tuning the integrity monitoring stage of the SPP and PPP algorithms increase significantly the continuity and reliability performances of the algorithms but at the expense of a heavier computational load.

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