Seafloor acoustic remote sensing with multibeam echo-sounders and bathymetric sidescan sonar systems

Abstract

Abstract, This paper examines the potential for remote classification of seafloor terrains using a combination of quantitative acoustic backscatter measurements and high resolution bathyme' try derived from two classes of sonar systems currently used by the marine research community: multibeam echo-sounders and bathymetric sidescans sonar systems. The high-resolution bathymetry is important, not only to determine the topography of the area surveyed, but to provide accurate bottom slope corrections needed to convert the arrival angles of the seafloor echoes received by the sonars into true angles of incidence. An angular dependence of seafloor acoustic backscatter can then be derived for each region surveyed, making it possible to construct maps of acoustic backscattering strength in geographic coordinates over the areas of interest Such maps, when combined with the highresolution bathymetric maps normally compiled from the data output by the above sonar systems, could be very effective tools to quantify bottom types on a regional basis, and to develop automatic seafloor classification routines.

The wavelet response as a multiscale characterization of scattering processes at granular interfaces

“…In particular, the concept of sharp and step-like interfaces may be strongly inadequate to represent the transition between bodies of heterogeneous material. Geophysical examples are volcanoes, the weathered subsurface [Exon et al, 1998;Vanneste al., 2001], and the shallow layers of sediments forming the seafloor [De Moustier et al, 1993;Augustin et al, 1996]. Ultrasonic imaging in both medical applications and non-destructive testing (NdT) are also faced with pitfalls of the step-like interface concept at transitions involving small-scale heterogeneous media like bones, fat and composite material.…”

Bathymetry of the Coral Reefs of Weizhou Island Based on Multispectral Satellite Images

“…Therefore, the ρ TOC image can finally be calculated by using Equation (6). The atmospheric correction approach is briefly presented in Figure 7.…”

“…Then, we change the aerosol optical thickness from 0.0 to 2.0 in intervals of 0.001 and run the 6S code for each of the aerosol optical thicknesses. Consequently, the radiance of the dark-object is transformed into different values of ρ TOC corresponding to different aerosol optical thicknesses by using Equation (6), which allows us to select the aerosol optical thicknesses that cause the ρ TOC of the near-infrared bands (Near-IR1 and Near-IR2 for WV-3 and Near-Infrared for ZY-3) to become as close as possible to zero (which is the optimal aerosol optical thickness).…”

“…2017, 9, 750 10 of 26 aerosol optical thicknesses. Consequently, the radiance of the dark-object is transformed into different values of TOC ρ corresponding to different aerosol optical thicknesses by using Equation (6), which allows us to select the aerosol optical thicknesses that cause the TOC ρ of the near-infrared bands (Near-IR1 and Near-IR2 for WV-3 and Near-Infrared for ZY-3) to become as close as possible to zero (which is the optimal aerosol optical thickness). Thereafter, the optimal aerosol optical thickness is then input into the 6S code to obtain the atmospheric correction coefficients.…”

“…The bathymetry of the seafloors has usually been determined using conventional echosounders [6][7][8][9]. However, as the echosounders are usually fixed in ships [7,10], such echosounder that the scan width of the echosounders will become narrow as the water becomes shallow.…”