Research on the Construction Method of High-Precision Ionospheric Delay Model for the Guangdong Region

The high-precision positioning technology of the Global Navigation Satellite System (GNSS) is a key support for intelligent drone inspections. However, in the low-latitude region of Guangdong Province, ionospheric activity is frequent and intense, and the correction accuracy of existing Global Ionospheric Maps (GIM) is insufficient in this area, often leading to significant positioning deviations during drone inspections. Therefore, this paper proposes an ionospheric delay correction method based on the Satellite-based Ionospheric Model (SIM). This method first employs carrier phase-smoothed pseudorange techniques to precisely extract the Total Electron Content (TEC) from dual-frequency GNSS observation data. Based on this data, a low-order polynomial model is independently established for each satellite, achieving accurate TEC correction and effectively avoiding the errors introduced by traditional mapping functions. Using empirical data from multiple Continuous Operating Reference Stations (CORS) in the Guangdong power grid, the results show that the SIM model significantly improves the correction accuracy of ionospheric delays, particularly in regions and periods of intense ionospheric activity. Under moderate solar activity conditions, the SIM model demonstrates stable correction accuracy, with a daily average bias of 0.1463 TECU and a standard deviation (STD) of 0.9192 TECU. Under high solar activity conditions, the daily average bias and standard deviation increase to 0.1469 TECU and 1.1937 TECU, respectively, indicating good adaptability and a much higher accuracy than GIM. The model also shows similar excellent performance in both winter and summer, confirming its strong environmental adaptability and stability. This provides an effective new solution for high-precision GNSS positioning and ionospheric delay correction in low-latitude regions.