A satellite-based method for modeling ionospheric slant TEC from GNSS observations: algorithm and validation

Ningbo Wang,Ang Liu,Andrzej Krankowski,Zishen Li,Wen Li,Kai Zhou,Hong Yuan

doi:10.1007/s10291-021-01191-2

Abstract

Total Electron Content (TEC) modeling is critical for Global Navigation Satellite System (GNSS) users to mitigate ionospheric delay errors. The mapping function is usually used for Vertical TEC ionospheric correction models for slant and vertical TEC conversion. But the mapping function cannot characterize TEC variation in different azimuths between the user and satellites. The ionospheric modeling error resulting from the mapping function tends to be bigger in middle and low latitudes. Therefore, a new algorithm for ionospheric Slant TEC (STEC) modeling with Satellite-based Ionospheric Model (SIM) is proposed in this contribution. Validation tests are carried out with GNSS observation data from the Crustal Movement Observation Network of China during different solar activities and in different seasons. The performance of SIM is compared with that of several commonly-used Global Ionospheric Map (GIM) and Regional Ionospheric Map (RIM) products. The results show that the STEC bias and STD of SIM are within 1.0 TECU and about 2.0 TECU, respectively, and SIM can correct over 90% STEC RMS errors, outperforming the GIM and RIM products. Consequently, the SIM algorithm can be a new option for high-accuracy ionospheric delay correction in regional and local GNSS networks.

Highlights

As a major error source in a Global Navigation Satellite System (GNSS), the correction accuracy of ionospheric delay directly affects the availability, accuracy, reliability, and integrity of GNSS services
We focus on direct Slant TEC (STEC) modeling to avoid modeling errors due to the mapping function
Unlike Vertical TEC (VTEC) correction models, we design and propose a GNSS ionospheric STEC modeling and correction method based on Satellite-based Ionospheric Model (SIM)

Summary

Introduction

As a major error source in a Global Navigation Satellite System (GNSS), the correction accuracy of ionospheric delay directly affects the availability, accuracy, reliability, and integrity of GNSS services. The development of rapid and real-time high-accuracy GNSS applications has become a research focus in recent years (Juan et al 2012; Shi et al 2012) This trend leads to the ever-growing demand for highly accurate and efficient ionospheric correction methods. Such corrections can help dual-frequency users obtain Ionospheric correction models such as broadcast models provided by major GNSS systems (IS-GPS 2004; Yang et al 2020; Montenbruck and González 2019), models using ground-based observation data for GNSS augmentation purposes (Li et al 2020), and single-station ionospheric models (Yasyukevich et al 2020) are used to mitigate ionospheric delay errors. With an increasing number of densely distributed GNSS reference stations, it is found that the accuracy of different ionospheric VTEC modeling functions is basically equivalent when the elevation mask is 15 degrees and above (Li et al 2014a)

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Conclusion