## 1 Introduction  
Earthquakes are considered to be relatively major natural disasters; each strong earthquake will cause serious damage and even heavy casualties. Achieving accurate earthquake prediction and mitigating the hazards caused by earthquakes is an urgent challenge that humanity seeks to solve [1; 2; 3]. In 1964, [PERSON] and [PERSON] [4] discovered a certain correlation between ionospheric anomalies and earthquakes during the preparation periods. Since then, many scholars have been dedicated to exploring the ionospheric disturbances that are potentially associated with earthquakes, attempting to establish a new method for earthquake study [5; 6]. In the previous research on the correlation between seismic events and ionospheric disturbances, two primary points have been explored: the analysis of disturbance characteristics prior to earthquakes based on ionospheric parameters; and the research on the physical mechanism of seismoionospheric coupling. The former includes analyzing and summarizing ionospheric anomalies associated with earthquakes, discussing their changes before and after seismic events, and refining the characterization of seismoionospheric perturbations. Currently, the parameters studied in relation to seismoionospheric disturbances include total electron content (TEC), F2 layer critical frequency (foF2), sporadic E layer (Es), ionospheric plasma parameters, electromagnetic radiation parameters, and high-energy particle flux, etc. [7; 8]. The latter example refers to the investigation of the coupling relationship between the lithosphere, atmosphere, and ionosphere. For example, [PERSON] et al. [9] discussed the potential impact of ionized gases released from the crust on the ionosphere, and [PERSON] et al. [10] investigated the relationship between ionospheric abnormalities and acoustic-gravity waves. Notably, the Russian scientist [PERSON] hassummarized a unified conceptual model which systematically verifies different types of earthquake precursors from different layers, thereby providing a theoretical foundation for earthquake prediction using ionospheric data [11; 12; 13]. At present, the analysis of pre-earthquake ionospheric anomalies based on satellite observation data such as GPS has received widespread attention [14; 15], and numerous studies have observed abnormal changes in the ionospheric TEC before earthquakes [16; 17]. For example, [PERSON] et al. [18] used GPS-based TEC data to statistically analyze three earthquakes above M7.0 on the Nepal and Iran-Iraq border, and they concluded that ionospheric precursors related to earthquakes may occur within 10 days. [PERSON] et al. [19] analyzed a Nepal earthquake with a magnitude of 7.8 through GPS-TEC data. While observing the pre-earthquake TEC anomalies, they further verified that the anomalies and earthquakes are correlated in terms of distance and time series scales. Based on GNSS TEC monitoring data, [PERSON] et al. [20] committed themselves to producing a TEC map covering the South American continent, which can better observe and analyze the spatiotemporal changes of TEC. However, the ionospheric pierce points (IPPs) between satellites such as GPS and ground-based receiving stations will vary unevenly with satellite motion. The observed data cannot directly reflect the temporal variation of ionospheric TEC at the same location and should be processed through mathematical interpolation or modeling methods, which may cause errors [21; 22]. The BeiDou navigation satellite system (BDS), which has been independently developed by China, is the only navigation system globally that incorporates geostationary Earth orbit (GEO) satellites [23; 24]. Geostationary orbits are affected by the oblateness of the Earth and the gravity of the sun and the moon, but the satellite can adjust itself, and the position deviation of the associated puncture point is further reduced.