Planar synthetic aperture processing (P‐SAS) to real acoustic data of underwater imaging

Abstract

Planar synthetic aperture technique has been validated on both simulated and tank data. It showed a significant improvement of 3D representation of bottom and subbottom. In this paper we present its application to real data acquired during sea experiments on a dump site. Data were acquired during the SITAR (Seafloor Imaging and Toxicity: Assessment of Risks caused by buried waste) project. The transmitter was a parametric array (TOPAS). Two central frequency were explored, 10 kHz and 20 kHz. The transmitter was fixed on a ROV which position was monitored. As P‐SAS algorithm was designed for data obtained on a regular planar grid important modification were required to handle real sea data and “realistic” navigation conditions (irregular grid): a “re‐arrangement” algorithm was designed for preprocessing actual data and correct for trajectory disturbances (in 2D). This algorithm is the re‐projection of data to a new (virtual) regularly grid. The algorithm was validated on tank experimental data prior to application to sea data. Both conventional and SAS data will be presented. A strata representation technique was used for analyzing the seafloor, the subbottom and the localization of buried objects on a dump site in the Baltic sea.