Normalization and Characterization of Multibeam Backscatter

Backscatter was derived from the Reson shallow water multibeam echosounders using custom software developed by researchers at the University of New Brunswick (Fredericton, Canada), for an area in the sanctuary, near Cape Flattery from Koitlah Point to Point of the Arches, and mosaiced at 1-meter pixel resolution. This process of normalizing the backscatter imagery significantly reduced the post-processing validation efforts that are required for the characterization effort. Textural classification of the sonar imagery suggests that nearly 58 percent of the seafloor in this area is covered by soft substrates such as mud or silt, 19 percent of the area is comprised of mixed sediment including cobbles, pebbles, gravel and boulders mixed with soft substrate, and over 23 percent of the total area is characterized by hard, complex rocky bottom.

Video from a towed camera sled, bathymetry data, sediment samples, and the backscatter have been integrated to describe geological and biological aspects of habitat. Polygon features have also been created and attributed with a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999). The data can be used with geographic information system (GIS) software for display, query, and analysis.

Keywords: Benthic, habitat mapping, sediment classification, multibeam backscatter normalization, textural analysis, Olympic Coast National Marine Sanctuary, essential fish habitat, groundtruthing, accuracy assessment