Improving Accuracy of Horizontal Flow Field Using Acoustic Tomography With Real-Time Station Position Correction

Abstract

High-precision and spatiotemporal flow field measurement in small-scale waters has a decisive impact on navigation and water resource management. Multitransmission rays and position drift, as two main difficulties in improving the accuracy of small-scale flow field, need to be solved urgently. In this article, four coastal acoustic tomography (CAT) systems are arranged in Qingyang Lake, Hunan, China, on March 1, 2022, for a short-term observation. As the GPS error and shipping caused station drift contaminate the reconstructed flow field, a real-time station position correction method, based on travel time and temperature, depth (TD) sensors, is applied in our inversion. The inversion range average current (RAC) is in agreement with forward calculation, which proves the reliability of the reconstructed horizontal flow field. Besides, comparisons of net flow and acoustic Doppler current profiler (ADCP) velocity are performed to validate the improvement of the real-time station position correction algorithm. The errors of the corrected net flow are less than 3.818 m 2/s, with a minimum of 0.0042 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}$ </tex-math></inline-formula> /s. The root-mean-square error (RMSE) between the CAT inversion results and the ADCP velocity is 0.123 m/s after correction, relatively reduced 5.95% than before correction. The smaller the RMSE, the higher the inversion accuracy, so the CAT method with real-time station position correction is feasible for high-precision horizontal flow field reconstruction.