Spatial Analysis of GNSS Measurements from an Equatorial Ionospheric Scintillation Monitoring Receiver (ISMR) Network

The ionosphere has always been a major limitation for GNSS positioning applications. Free electrons in the ionosphere perturb the propagation of GNSS radio signals involving both refraction and diffraction effects. In particular, small-scale ionospheric irregularities generated by different physical processes may cause scattering effects on GNSS signals, producing rapid fluctuations of the signal phase and amplitude as a result. Such scintillations of GNSS signals are responsible for critical consequences regarding applications, such as precise positioning, due to many resulting effects: cycle slips, signal power fading, receiver loss of lock and poor resulting satellite geometry.
Ionospheric Scintillation Monitoring Receivers collect high-rate GNSS data. Specific scintillation parameters, such as the well-known S4 and Phi60 indices, are built on high-rate measurements performed on GNSS signals and provide additional information to characterize the intensity of such an event occurring at a specific geographic location at a given time.
Spatial Statistics belong to the field of Spatial Analysis, Geography and GIS (Geographic Information System). This discipline allows to perform analyses of data which are localised in space. Ionospheric Scintillation observations achieved by ISMR stations can be characterized by a set of attributes (S4, Phi60, Rate of TEC, etc.) including also the geographic location of their respective Ionospheric Pierce Point (IPP). By combining the simultaneous Multi-GNSS ISMR measurements from a network of ISMR stations, we can obtain a spatially denser data set, able to support spatial statistics tests. The idea of our research is to provide a spatio-temporal analysis of ionospheric scintillation events over Equatorial regions by applying spatial statistics on ISMR Multi-GNSS measurements.
In particular, by using spatial statistics, we aim to resolve specific issues regarding ionospheric scintillation data from an ISMR network established in Brazil. The research consists in spatially describing the data set, detecting and measuring potential spatial autocorrelation, determining the scale of the spatial dependency and finally producing an interpolated scintillation sky map at a given time.
In terms of applicability of the methodology, our research project consists in exploiting the spatio-temporal analysis performed on ionospheric scintillation data in order to improve the performances and the reliability of Absolute GNSS Positioning algorithms under moderate ionospheric scintillation conditions. By assessing correlations existing between specific ISMR data and classic GNSS observations, the method could be extended to a more general usage which would be independent of ISMR measurements.