Quantitative imaging of calibrated acoustic backscatter data from the seafloor

Abstract

Two factors have often led to the neglect of instrument calibration and the loss of information in the imaging process: the power of the image and the convenient signal processing expedient of disregarding the physical nature of data. Seafloor imaging by sonar is a case in point. Notwithstanding ambitions and needs to remotely detect and identify bottom objects, determine seafloor properties, and quantify benthos, among other things, images of acoustic backscattering data are often used, misleadingly, as proxies for physical data. Since image processing is inherently nonlinear, the loss of physical data is immediate. Three processes that are essential to the attainment and maintenance of the physical nature of backscattering data are elaborated: sonar calibration to determine the transfer characteristics of the sonar, range compensation that addresses both geometric and radiometric factors, and beam pattern measurement or estimation.