Inference of manganese nodule coverage from Sea Beam acoustic backscattering data

Abstract

Normal incidence reflectivity from a manganese nodule field was measured with a 12 kHz Sea Beam multibeam echo‐sounding system, aboard the R/V Thomas Washington and used to infer nodule coverage. A reflectivity map of the area was produced using the intensity of the specular return from each ping. The patchiness of the nodule coverage is evidenced by definite highs and lows in the reflectivity pattern. Ground truth was provided by near‐bottom acoustic measurements and photographs taken with the Deep Tow instrument package of the Marine Physical Laboratory. Agreement between the simple nodule coverage predictions from Sea Beam acoustic data and the bottom photographs taken throughout the area is 98 percent. Although the Sea Beam system is limited in its dynamic range, this paper shows that it can be used very effectively to determine both topography and nodule coverage in potential mining areas.