A coastal acoustic tomography inverse method based on Chebyshev polynomials and its application in Zhoushan field experiment

Seven sets of shelf-contained type coastal acoustic tomography systems (CATs) were deployed in Zhitouyang Bay near the Zhoushan Island during July 12 to 13, 2009 to measure current structures at 3-min interval. The acoustic ray travel time tomography algorithm based on Chebyshev polynomials and truncated total least squares (TTLS) technology for reconstruction of two-dimensional flow field are constructed and tested using the CAT observation data. It can completely avoid spatial periodic of inverse results using Chebyshev polynomials. The TTLS technology, which simultaneously considers operator error and observational noise in system, is used for solutions of ill-posed problem. Variation of tidal current fields from food tide to ebb tide and tidal vortexes are well reconstructed by the inverse analysis of travel-time difference data. The investigation suggests that the CAT is a powerful tool to continuously map tidal current fields in the coastal seas. The coastal acoustic tomography inverse method based on Chebyshev polynomials and truncated total least squares technology can substantially improve reconstruction of current field and is a promising alternative method for the ocean acoustic tomography inverse problem.