Metrology of the Acoustic Seafloor Response: How to accurately estimate backscatter and its intrinsic uncertainty using single-beam echosounder

Its measurements have been widely extended in hydrography using predominantly bathymetric echosounders, and they are used in diverse applications such as habitat mapping, seabed characterisation or classification. In recent decades, numerous theoretical models have also been developed to study its link with physical or heuristic bottom parameters. While analysing how these three domains (measurement, application, and theory) deal with the seafloor acoustic response, it appeared that the nature itself of the seafloor acoustic response is equivocal.

The work presented here proposes a relationship between the three uses of the seafloor acoustic response. Based on statistical and physical hypotheses, a metrological method is established, connecting seafloor response measurements, applications and theory. In particular, the deterministic backscatter parameter derived theoretically is usefully linked to the stochastic nature observed in practice during backscatter measurements. This yields
a method for accurately estimating backscatter values from bathymetric echosounder data: the best choice of backscatter estimator is justified based on analytical calculations, and ways to represent its uncertainties are proposed. Theoretical hypotheses are validated using real data from handmade single-beam echosounders tested at ENSTA Bretagne (France) and at the University of Bath (UK). After application of the method to survey data, its benefits, limits, and future implementation are discussed.