The ionosphere is one of the largest natural error sources in Global Navigation Satellite System applications, especially during periods of strong solar activity. Existing global ionosphere models help correct part of that error, but their spatial resolution is often too coarse to capture sharp, localized gradients. At the same time, irregular plasma structures can trigger signal scintillation, cycle slips, and sudden drops in positioning stability. Earlier studies documented these hazards, yet key gaps remained: how different ionosphere models perform under steep regional gradients, and how storm-time electrodynamic processes physically connect to irregularities and positioning degradation. Based on these challenges, deeper research is needed on regional ionospheric structures and their impacts on GNSS positioning.
Researchers from the Institute of Geology and Geophysics, Chinese Academy of Sciences, together with collaborators from the Aerospace Information Research Institute of CAS, Nanjing University of Information Science and Technology, and Shandong University, reported (DOI: 10.1186/s43020-026-00191-2) in Satellite Navigation in 2026 that regional ionospheric structures in the Asian sector can strongly alter both standard point positioning (SPP) and precise point positioning (PPP), with sharp TEC gradients and storm-driven post-sunset irregularities emerging as two major sources of error.
Using observations from more than 300 GNSS receivers across Asia, along with ionosonde and incoherent scatter radar measurements at Sanya, the team traced how medium-scale and small-scale ionospheric structures affect positioning in different ways. They identified steep TEC gradients exceeding 2 TECU per degree, concentrated mainly between 20°N and 30°N. Those gradients exposed a major weakness in widely used global ionosphere models: most were too coarse to reproduce the real structure. CASG and JPLG performed better than other products, but even JPLG left more than half of the strongest gradients unresolved. When such gradients appeared, SPP errors increased, while CASG reduced those errors by about 0.5 to 2 meters compared with many alternatives. The study then turned to two geomagnetic storms. During the 1 December 2023 event, an under-shielding penetration electric field drove upward plasma drift, intensified post-sunset irregularities, and degraded kinematic PPP accuracy from under 10 centimeters to beyond 1 meter, in some cases reaching meter-level to 10-meter-scale errors. In contrast, during the 10 May 2024 storm, an over-shielding electric field drove downward drift, suppressed the usual post-sunset irregularities, and prevented the extra PPP errors they normally trigger.
“This study shows that the ionosphere is not just background noise for satellite navigation,” the findings suggest. “Its regional structures can rapidly reorganize positioning conditions, and storm-time electric fields can push the system in opposite directions—either amplifying errors or suppressing them.” That insight matters because it shifts the focus from simply asking whether a geomagnetic storm is occurring to asking what kind of electrodynamic process is unfolding, where, and at what time of day.
The work has clear operational value. It suggests that GNSS users in Asia—from surveying systems to transport platforms and autonomous technologies—could benefit from warnings that track not only storm intensity but also steep TEC gradients and the direction of storm-time electric fields. It also points to practical model improvements: finer longitudinal resolution, better use of multi-constellation data, and more realistic multi-layer ionosphere representations. Rather than treating all space weather as uniformly harmful, the study shows that some storm-time conditions may actually prevent daily irregularity-related positioning failures. That makes the future of GNSS forecasting not just more accurate, but more nuanced and more actionable.
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References
DOI
10.1186/s43020-026-00191-2
Original Source URL
https://doi.org/10.1186/s43020-026-00191-2
Funding Information
This work was supported by National Natural Science Foundation of China (42530201), National Key R&D Program (2022YFF0504400), Basic Research Program of Jiangsu (BK20250747), and National Key R&D Program of China (2025YFF0512302).
About Satellite Navigation
Satellite Navigation (E-ISSN: 2662-1363; ISSN: 2662-9291) is the official journal of Aerospace Information Research Institute, Chinese Academy of Sciences. The journal aims to report innovative ideas, new results or progress on the theoretical techniques and applications of satellite navigation. The journal welcomes original articles, reviews and commentaries.