Backscatter measurements by seafloor‐mapping sonars. Guidelines and Recommendations

Marine scientists have long recognized the potential of using remotely‐sensed data as a proxy of biophysical indicators. Such data are most often acquired using sonar systems, since acoustic waves are the most suitable mechanism for transmitting information through the water column. Research and development that look at using marine acoustics for environmental science spans the entire spectrum from fundamental science to engineering. One research group that supported and encouraged this line of research is the GeoHab group, an international association of scientists focusing on marine Geological and biological Habitat mapping. GeoHab started in 2001 as a group of research scientists gathered to discuss potential and advances of using remotely‐sensed data to develop quantitative study on the relationships between seafloor substrate and benthic ecosystems. In 2013, QPS organized a parallel event at the GeoHab annual meeting in Rome on "Multibeam Backscatter – State of the Technology, Tools & Techniques". It is during this workshop, attended by about 100 participants, that the need for a compendium on backscatter acquisition, processing and interpretation came up. The Backscatter Working Group (BSWG) was created in the wake of the workshop and a first draft of the guidelines and recommendations was presented one year later at the 2014 GeoHab meeting in Lorne, Victoria, Australia and led to its release at the 2015 GeoHab conference in Salvador, Brazil. The founding ideas of the BSWG originate from the discussions that happened at the QPS workshop. These discussions identified a patent lack of commonly accepted acquisition procedures and processing methodologies of backscatter data recorded with multibeam echosounders (MBES) commonly used for seafloor surveys. Similarly, gaps in the documentation and literature pertinent to backscatter theory and applied operations were recognized. Concerning the acquisition procedures, it was found that a lack of consistency between the backscatter acquisition systems proposed by various manufacturers had never been addressed, and was widening because of the rapidly evolving development; the same issue is valid, too, for successive generations of sonars built by one same manufacturer, or the performance continuity of one same system along its life cycle. This lack of consistency was regarded as an obvious hindrance to the progress of backscatter science that all participants agreed was possible. The vision of the working group can be worded thus: "Backscatter data acquired from differing sonar systems, or processed through differing software tools, generate consistent values over a same area under the same conditions; these data are scientifically meaningful and usable by end‐users from all application domains (geoscience, environment, hydrography, industry, fisheries, monitoring, cultural…)". With this in mind, the aim of the BSWG and of the report presented here is twofold: (1) agree on, and provide, guidelines and best practice approaches for the acquisition and processing of backscatter data from seafloor‐mapping sonars; and (2) provide recommendations for the improvement and further development of seafloor‐mapping sonar systems for acquisition of backscatter data and related processing tools. Suggested reference: Lurton, X.; Lamarche, G. (Eds) (2015) Backscatter measurements by seafloor‐mapping sonars. Guidelines and Recommendations. 200p. DOI: 10.5281/zenodo.10089261