Through-the-sensor sediment characterization from autonomous underwater vehicle sonar systems

Abstract

Ocean bottom sediment type is a key parameter in understanding physical processes such as sediment transport and object burial as well as acoustic processes such as propagation and backscatter. However, direct methods such as coring and grab samples are time-consuming and coverage limited. The analysis of normal-incidence echo sounding has proven to be a reliable technique for certain frequency ranges. For this method, a clear understanding of the physical processes such as scattering and reflection is critical. For higher coverage, the normal-incidence echo sounder technique can be applied to through-the-sensor measurements. This is attractive since it requires no additional equipment particularly important to autonomous underwater vehicle operations. However, through-the-sensor measurements have the additional complications of understanding hardware and signal processing algorithms that were not specifically designed for sediment characterization or normal-incidence echo sounding. In this talk, measurements from two sensors, the light-weight conformal array and the small synthetic aperture minehunter, are analyzed for sediment type. The results are compared with ground truth data. Challenges and issues involved with using these sensors for sediment characterization will be discussed. [Work supported by ONR, Ocean Acoustics.]