Research on Sound velocity model construction method in GNSS-A underwater positioning

Abstract GNSS-A technology is a submarine positioning technique used to establish ocean control networks, and its positioning results are primarily affected by errors in ocean sound velocity. To address this issue, this paper analyzes the spatial representativeness error of the weighted average sound velocity based on the GNSS-A positioning principle. It also explores the construction method of a sound velocity model in the time domain using the average sound velocity. A sinusoidal diurnal variation model for sound velocity is developed through expanded fitting. Finally, actual measured data is used to perform GNSS-A submarine positioning, verifying the effectiveness of the sound velocity model. The results show that when the horizontal distance of the sound ray is less than 1.7 times the water depth, the average sound velocity does not introduce significant systematic errors. The constructed sound velocity model aligns with local solar elevation patterns, improving the unit weight error of GNSS-A positioning results by several decimeters and controlling the mutual difference of positioning results from different tracks to the decimeter level.