Abstract:This paper uses GNSS signal-to-noise ratio (SNR) data to obtain the dam water level changes. Based on the multi-path signal characteristics of water surface reflection, this paper analyzes the influence of signal frequency, altitude angle range and arc length on the water level inversion results of power station dams. We compare the water level inversion results with the measured water level data of the dam. The experimental results show that the two results have good consistency; the correlation coefficient is above 0.9; the water level retrieval accuracy of the GPS system is 0.1-0.15 m; the water level retrieval accuracy of the BDS system is 0.35-0.45 m; and the combined inversion accuracy of the GPS and BDS systems is 0.1-0.13 m, which is better than the single system retrieval precision.