Inversion of sound speed profile in shallow water with irregular seabed

Horizontal deflection often occurs when a ray propagates in shallow water with an irregular sea bottom. This makes it difficult to determine the eigen-ray trajectory and transmission time. A new method for seeking eigen-rays in three-dimensional space is proposed. SSP has been inverted from experimental data in the South China Sea using the fastest eigen-ray transmission times to form the cost function. In order to improve the speed of the inversion, the algorithm was transformed from a non-linear optimization to the solution of linear equations by using the perturbation method. The experimental results indicate that the precision of SSP inversion can be enhanced dramatically by considering horizontal deflections of eigen-rays. The inversion speed can be improved sufficiently for real-time monitoring of SSP with reasonable precision by using the perturbation method.