Analysis of multibeam-Hydrosweep echo peaks for seabed characterisation

Echo-peak data of outer and normal incidence beams from five different Sout hern Ocean bottom topographic regions have been analysed. The Rice and Extr emal probability density function (PDF) statistical approaches reveal that the seabed roughness is, in general, Gaussian in nature except in the case of the Kainan Maru seamount summit (area D). The outer beams of the Enderby abyssal plain (area C) echo-peak PDF statistics reveal the highest possibl e large-scale feature dominance. Interestingly, Extremal PDF fit parameters (x) from the Agulhas Basin (area A) show a less dominant large-scale rough ness than in the case of area C. Large-scale feature dominance up to 15 deg rees beam angle is observed in the case of mixed roughness seabeds such as area B (southwest Indian ridge) and area E (Meteor Rise). No increase in th e 30 degrees -beam Extremal PDF parameters is observed in these areas. Maxi mum microtopographic roughness is documented in area D on the summit of Kai nan Maru seamount. The estimated fit parameters using Extremal statistics o f outer-beam peak data provide a better understanding of the scattering pro cess. Previously determined power law and volume roughness parameters using composite roughness theory are given for the five different areas. These s upport the results obtained using Rice and Extremal PDFs. The existence of higher volume roughness parameters and power law parameters for medium-scal e roughness, along with dominant microtopographic features, are evident fro m the results of this study.