A Study on the Estimation of Source Bearing in an ASA Wedge: Diminishing the Estimation Error Caused by Horizontal Refraction

The performance of warping transformation in diminishing the error in underwater source-bearing estimation, caused by horizontal refraction effects (also named 3D effects), is studied. First, the capability of warping transformation for separating the normal modes, as well as their direct and horizontally refracted paths, in a standard Acoustical Society of America (ASA) wedge is demonstrated. Second, the error values for source bearing estimation in three different manners, i.e., using the full signal, using its component corresponding to the first mode, and using the component of the latter corresponding only to the direct path are compared for the same wedge case. The results show that the estimation error can be significantly reduced by beamforming, with only the first mode, or using the direct path of the first mode in cases where there exists a horizontally refracted path of the first mode.