The reflectometry method and accuracy analysis of the sea surface height based multi-observation from BDS

With the continuous development of the BeiDou Navigation Satellite System (BDS), sea surface height retrieval based on BeiDou interferometric reflectometry (BDS-IR) has attracted increasing attention. In this paper, we introduce sea surface height retrieval methods based on BDS SNR, triple-frequency carrier phase combinations, and single-frequency carrier pseudorange combinations, and also analyse the effects of signal types and signal frequencies on BDS-IR sea surface height retrieval. Using 120 days of BDS observation data from the AT01 station, the retrieval results show that the RMSE of the SNR-based retrieval model, triple-frequency carrier phase combination model, and single-frequency carrier pseudo range combination model are 0.199 m, 0.189 m, and 0.204 m, respectively, with bias of 0.126 m, 0.067 m, and 0.130 m, respectively. The SNR-based model performs the best, and the triple-frequency carrier phase combination model outperforms the single-frequency carrier pseudo range combination model. All BDS frequencies demonstrate high retrieval accuracy, with the RMSE ranging between 0.16 m and 0.19 m. Excluding the S7I, which provides an average of only 5.5 retrieval points per day, the other frequencies produce about 50 retrieval points per day, meeting the requirements for high-precision sea level monitoring. BDS-2 and BDS-3 exhibit comparable retrieval accuracy, with RMSE of 0.163 m and 0.185 m, respectively. This study will further improve GNSS-IR water level monitoring technology and provide accuracy support for future research.