Eliminating Potential Errors Caused by the Thin Shell Assumption: An Extended 3D UNB Ionospheric Modelling Technique

摘要

Ionospheric modelling has become an focus area within the global navigation satellite system (GNSS) community using several satellite-based augmentation systems (SBAS) (e.g., Wide Area Augmentation System (WAAS), European Geostationary Navigation Overlay Service (EGNOS), and MTSAT Satellite-based Augmentation System (MSAS)). Data-driven models have been applied with these systems and demonstrated as the best candidates for post-processing and other real-time applications due to their real-time applicability and relatively higher accuracy compared to empirical ionospheric modelling techniques. In this paper, our objective is to improve the accuracy for the real-time positioning applications. To achieve this, we extended the University of New Brunswick-Ionospheric Modelling Technique (UNB-IMT) from two-dimensions (2D) to three-dimensions (3D) by modelling the vertical dimension of the ionosphere using empirical orthogonal functions (EOFs) to eliminate the potential mapping function errors. The benefits of the new proposed modelling technique are demonstrated in a small regional network using post-fit residuals, estimated vertical total electron content (vTEC), as well as the repeatability of the estimates of differential code biases (DCBs). The ionospheric results from 3D UNB-IMT are also compared with those from widely-used 3D spherical harmonic (SH) models to show the beneficial effect of improving sensitivity owing to the effective and meaningful parameters in the model.