
%0 Journal Article
%A Kloser, R. J. 
%A Bax, N. J. 
%A Ryan, T. 
%A Williams, A. 
%A Barker, B. A. 
%T Remote sensing of seabed types in the Australian South East Fishery; development and application of normal incident acoustic techniques and associated 'ground truthing'
%J Marine and Freshwater Research
%D 2001/09/26
%V 52
%N 4
%P 475-489
%K 
%R https://doi.org/10.1071/MF99181
%U https://www.publish.csiro.au/paper/MF99181 
%X Calibrated acoustic backscattering measurements using 12, 38 and 120 kHz were collected over depths of 30&#8211;230 m, together with benthic epi- and in-fauna, sediments, photographs and video data. Each acoustic ping was envelope detected and digitized by echo sounder to include both the first and second echoes, and specifically designed software removed signal biases. A reference set of distinct habitat types at different depths was established, and a simple classification of the seabed combined both biological and geological attributes. Four seabed types were identified as having broad biological and geological significance;the simple acoustic indices could discriminate three of these at a single frequency. This demonstrates that the acoustic indices are not directly related to specific seabed properties but to a combination of seabed hardness and roughness attributes at a particular sampling frequency. The acoustic-derived maps have greater detail of seabed structure than previously described by sediment surveys and fishers&#8217; interpretation. The collection of calibrated digital acoustic data at multiple frequencies and the creation of reference seabed sites will ensure that new shape-and energy-based feature extraction methods on the ping-based data can begin to unravel the complexities of the seabed. The methods described can be transferred to higher-resolution swath-mapping acoustic-sampling devices such as digital side-scan sonars and multi-beam echo sounders. 
