The GeoHab Backcatter Working Group (BSWG) is an international group of experts on seafloor backscatter data acquired with seabed mapping sonar systems such as multibeam sonar systems, with the objective to improve the quality, consistency, and usefulness of backscatter data.

Background:

BSWG was created at the GeoHab 2013 conference in Rome, Italy. The decision to form this group was taken at a pre-conference workshop, titled “Multibeam Backscatter – State of the Technology, Tools, & Techniques” and organized by QPS and others on 5 May 2013, gathering nearly 100 specialists of the domain. The main issues discussed were data quality control, the need for normalized acquisition and processing procedures, and the expectation for better documentation from sonar manufacturers and software developers on their respective products.

Purpose:

The ultimate intention of the BSWG is that “backscatter data acquired from differing systems, or processed through differing software tools, generate consistent values over a same area under the same conditions; and that these data are scientifically meaningful and usable by end-users from various application domains (geoscience, environment, hydrography…)”.

Within this framework, the purpose of the Working Group is to propose:

• To users: guidelines or best practice approaches for the acquisition and processing of backscatter data from seafloor-mapping sonars.
• To sonar manufacturers and software developers: recommendations for the improvement and further development of systems and processing tools.

Operation:

The working group progresses through a series of in-person meetings and workshops (usually, at GeoHab conferences), virtual workshops, and circulating documents. BSWG is open to all interested participants but the onus is on a set of core members (see below) to keep the momentum and focus.

Current organization:

As of 2022, the BSWG is organized in 8 thematic branches:

Backscatter Data Manufacturers and Calibration
Co-leads: Marc Roche, Ridha Fezzani
Scope: BSWG Calibration addresses all aspects of backscatter calibration issues, such as (1) defining in-tank and at sea calibration procedures, (2) backscatter post-calibration tools, and (3) enticing manufacturers to ensure transparency in their backscatter measurements.

Backscatter Data Acquisition
Co-leads: Jonathan Beaudoin, Margaret Dolan
Scope: BSWG Acquisition focuses on all aspects of data acquisition that support the goal of having great backscatter results. This includes (1) survey planning, (2) sonar configuration and operation, (3) operational best practices that are common for all sonar makes and models, (4) real-time QA, and (5) general survey practices that contribute to good results. The aim is to take care of getting quality data such that post-processing is as simple as possible. Why “fix it in post-processing” when you can just collect it correctly in the first place?

Backscatter Data Processing
Co-leads: Luciano Fonseca, Jonathan Beaudoin, Alexandre Schimel
Scope: BSWG Processing is concerned with all aspects of multibeam sonar backscatter data processing, such as (1) existing and emerging software resources (both open-source and commercial), (2) information about processing techniques, (3) metadata for backscatter data products, (4) software intercomparison studies, and (5) methods for harmonisation of multi-source mosaics. We aim to push for improvements in overall processing techniques and provide advice to both software developers and users.

Backscatter Data Analysis and Interpretation
Co-leads: Tim Le Bas, Craig Brown
Scope: BSWG Interpretation is concerned with (1) investigating the methods of interpretation and analysis of backscatter data, (2) using and sharing best-practices and software such as AI and Machine Learning, and (3) understanding the drivers of backscatter to aid end-products in terms of classification and final usage.

Backscatter Data Variability and Monitoring
Co-leads: Giacomo Montereale Gavazzi, Marc Roche
Scope: BSWG Variability is concerned with all aspects of backscatter data variability in space and time. The branch is interested in understanding the intrinsic and extrinsic variability of backscatter data, referring to both wanted and unwanted backscatter signal fluctuations, that is, those of interest to characterise a given target of interest, and those that “pollute the signal”, hence requiring filtering. The branch is interested in the application of backscatter data to detect and monitor seafloor changes.

Multispectral multibeam acoustic data
Co-leads: Benjamin Misiuk, Jens Schneider von Deimling, Craig Brown
Scope: BSWG Multispectral is focused on investigating the uses and applications of multifrequency (i.e., “multispectral”) multibeam echosounder data, including both bathymetric and backscatter measurements. Research associated with this branch focuses on ways in which data collected using multiple frequencies simultaneously may be analysed in new and unique ways for a range of purposes. These may include thematic mapping topics such as characterising benthic habitats or surficial substrates, but also integration of shallow subsurface information by acoustic penetration using lower frequencies. Novel approaches address data processing, secondary feature derivation and engineering, and characterization of the sediment water interface and shallow subsurface. Additional comparative exercises will explore the benefits of employing multiple acoustic frequencies compared to a single frequency for habitat mapping purposes.

Multibeam Water-Column Data
Co-leads: Peter Urban, Sally Watson
Scope: BSWG Water-Column focuses on (1) helping folks around the world to connect their water-column data research with others, (2) sharing relevant news, science and updates on water-column data research, and (3) being a place where conferences, workshops and proposal ideas can be announced/developed.

BSWG Communications
Co-leads: Anne-Sophie Piette, Massimo Di Stefano, Vincent Lecours
Scope: BSWG Communications is in charge of updating the BSWG website, managing resources, maintaining the mailing lists, and facilitating communication within and among branches.

Links and resources:

• BSWG 2015 report “Backscatter measurements by seafloor‐mapping sonars. Guidelines and Recommendations”
• Marine Geophysical Research Special Issue “Seafloor Backscatter Data from Swath Mapping Echosounders: from Technological Development to Novel Applications”. 2018. 39 (1-2).
• BSWG Youtube channel
• BSWG Public Dropbox folder