GNSS-IR tide level inversion and tidal wave analysis methods and accuracy evaluation

Sea level changes have significant impacts on marine ecosystems and human production and life. Accurate tidal level monitoring can provide data support for the safety of coastal cities and meteorological and climate research. The Global Navigation Satellite System Interferometric Reflectometry (GNSS-IR) technology, with its advantages of all-weather operation, low cost, and high temporal resolution, has become an important tool for tidal level inversion and tidal wave analysis. To explore the inconsistency between tidal level inversion accuracy and tidal wave analysis accuracy, data from four major satellite navigation systems at the HKQT station in Hong Kong, China, from August 1 to August 30, 2024, were selected for tidal level inversion and tidal wave analysis. The results show that after applying sea surface dynamic corrections and eliminating outliers using the threefold median absolute deviation (3σ) principle, the tidal level inversion accuracy reached 12～14 cm, and the tidal wave analysis accuracy reached 8～10 cm. The sea surface dynamic corrections effectively reduced errors in both tidal level inversion and tidal wave analysis, with an average improvement of 6.93% in tidal level inversion accuracy and 10.18% in tidal wave analysis accuracy. Differences in accuracy were observed among the systems for both tidal level inversion and tidal wave analysis. After applying the 3σ principle to eliminate outliers and performing sea surface dynamic corrections, the BDS system achieved the highest tidal level inversion accuracy among the four systems at 12.53 cm, while its tidal wave analysis accuracy was 8.42 cm, ranking second among the four systems and only 2.81% lower than the GPS system, which had the highest tidal wave analysis accuracy.