Max-min Eigenvalue Detection for Small-scale Ionospheric Anomaly at low latitudes China

Tong Liu, Yiping Jiang, Jian Liu, Guochang Xu

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review


Beidou Satellite Based Augmentation System (BDSBAS) broadcasts correction and integrity information to the user via a 5°×5°grid model in its most service areas. Frequent anomalies of the ionosphere at low latitudes in China would degrade the performance of the BDSBAS and introduce integrity threats to single-frequency civil aviation users. Previous studies have focused on the effects
of ionospheric anomalies on the grid model. However, the distance between two
adjacent grid points is about 540-600km in the low latitudes of China, but most of the Plasma Bubbles (PBs) has an impact range of about 100km. Since SBAS
ground stations are sparse and planar fit may be ineffective at low latitudes, such small-scale ionospheric anomalies are not always captured by the grid model and reflected in the Grid Ionospheric Vertical Error (GIVE), leading to potential safety risks. An effective remedy is the use of dense observatories in the focused regions and the direct design of anomaly detection algorithms from ionospheric observations. Therefore, an improved Maximum and Minimum Eigenvalues (MME) detection is proposed. The maximum and minimum eigenvalues of the covariance matrix are used to calculate the metric of a small-scale ionospheric anomaly. The thresholds can be derived from the Tracy-Widom distribution of the test metric. Several examples demonstrate the correlation between MME and the rate of the total electron content index (ROTI). The diurnal variation of the active ionospheric year 2015 using observational data from Hong Kong, China, shows that events exceeding the threshold occurred mainly at night, especially from 20:00 to 0:00. Besides, the ionospheric equatorial anomalies show seasonal variations, occurring mainly in spring, followed by autumn. The locations of ionospheric anomalies distribute randomly. This study could serve as an effective supplement to the lowlatitude BDSBAS to protect users from the threat of PB.
Original languageEnglish
Title of host publicationChina Satellite Navigation Conference
Number of pages9
Publication statusPublished - May 2021


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