Thematic accuracy assessment of acoustic seabed data for shallow benthic habitat mapping

Abstract

A single beam acoustic ground discrimination system (AGDS) was used to survey 1.25 km 2 of shallow (< 20 m depth) seabed on the northeast coast of Tasmania, Australia. This paper investigates the uncertainties associated with the qualitative interpretation of real time and post-processed acoustic signal, and the effect of track spacing on the mapping of rocky reef distribution. The survey was repeated with different track spacing (50 m, 100 m, 200 m and 50 × 200 m shore normal) to investigate the influence of data density and 'knowledge based interpolation' validated against direct measurements made with an underwater video camera. Habitat area calculations varied substantially only with the 50 × 200 m transect. These results have important implications for the qualitative assessment and application of AGDS technology in shallow water marine habitat mapping.

What can a low-cost fish-finder tell us about the seabed?

“…Our results are comparable with those obtained using more expensive scientific echosounders. For example, Halley & Bruce (2007) working with a Simrad single-beam scientific echosounder (the most popular scientific echosounder), obtained κ = 0.64 and Che Hasan et al (2012) obtained similar κ values (between 0.59-0.72) using multibeam echosounders. We should note however that most of these studies classified more than two bottom classes (and accuracy naturally decreases with the number of classes).…”