Abstract
Multibeam echosounders are becoming widespread for the purposes of seafloor bathymetry mapping, but the acquisition and the use of seafloor backscatter measurements, acquired simultaneously with the bathymetric data, are still insufficiently understood, controlled and standardized. This presents an obstacle to well-accepted, standardized analysis and application by end users. The Marine Geological and Biological Habitat Mapping group (Geohab.org) has long recognized the need for better coherence and common agreement on acquisition, processing and interpretation of seafloor backscatter data, and established the Backscatter Working Group (BSWG) in May 2013. This paper presents an overview of this initiative, the mandate, structure and program of the working group, and a synopsis of the BSWG Guidelines and Recommendations to date. The paper includes (1) an overview of the current status in sensors and techniques available in seafloor backscatter data from multibeam sonars; (2) the presentation of the BSWG structure and results; (3) recommendations to operators, end-users, sonar manufacturers, and software developers using sonar backscatter for seafloor-mapping applications, for best practice methods and approaches for data acquisition and processing; and (4) a discussion on the development needs for future systems and data processing. We propose for the first time a nomenclature of backscatter processing levels that affords a means to accurately and efficiently describe the data processing status, and to facilitate comparisons of final products from various origins.
Highlights
Exploration of the ocean floor relies widely on the use of underwater acoustics for seafloor mapping (Bourillet et al 1996; Brown et al 2012; Pratson and Edwards 1996)
We provide four categories of recommendations regarding the improvement of current seafloor-mapping sonar functionalities: Design and implementation of dedicated backscatter calibration and measurement tools
The Backscatter Working Group (BSWG) has completed its initial mandate within a selfimposed duration of two years: the project had to be long enough to address such complex topics at a level of details sufficient to provide useful results
Summary
Exploration of the ocean floor relies widely on the use of underwater acoustics for seafloor mapping (Bourillet et al 1996; Brown et al 2012; Pratson and Edwards 1996). The BSWG elected to limit its activity to seafloor backscatter, leaving aside other applications such as water column investigation This decision was justified mainly by (1) the recent and rapid evolution of hardware, software and methodologies pertinent to water column from MBES, which was likely to result in obsolete information by the time the report would be published; (2) the existence of a similar project recently conducted by the International Council for the Exploration of the Sea (ICES) in the field of fisheries sonar (Demer et al 2015); and (3) the desire to restrict the BSWG’s tasks to be manageable. All the calibration results and modifications applied to the sonar should be accurately reported and recorded for future use and reference
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