Circular Analysis of Long-Term GNSS Horizontal Positioning Error Time Series Observed in the Sub-Equatorial Region

Ionospheric effects characterisation is a prerequisite for the development of robust and resilient GNSS Positioning, Navigation, and Timing (PNT) services needed for the modern GNSS-dependent society and civilisation. Here, we present the results of the study of circular properties of single-frequency commercial-grade Global Positioning System (GPS) horizontal positioning errors in the sub-equatorial scenario. The research reveals daily occurrence patterns of GNSS performance degradation in the observed region, thus setting the stage for improvements of the GNSS ionospheric error corrections.