|Titre||ACOUSTIC IMAGERY FOR BENTHIC HABITATS MAPPING AND MONITORING|
|Type de publication||Journal Article|
|Year of Publication||2010|
|Auteurs||Fournier, J, Baltzer, A, Godet, L, Panizza, Ade Castro|
|Journal||Geomatic Solutions for Coastal Environments|
Some shallow subtidal marine benthic habitats cannot be well mapped using classical remote sensing techniques such as satellite imagery or aerial photographs. Conversely, sidescan sonar is a very useful tool for mapping subtidal benthic features and monitoring some threatened habitats over small or large areas. Despite the increasing use of multibeam technology in benthic habitat mapping, sidescan sonar is efficient in detecting small-scale features in coastal environments, such as Zostera marina beds, Lanice conchilega and Serpula vermicularis reefs or large-scale features such as maerl red marine algae Lithothamnium calcareum beds. Sidescan sonar is a method of underwater imaging using beams of acoustic energy transmitted out to each side of the towfish and across the seafloor. The imagery is a reflection of the acoustic energy that is backscattered from the seafloor and is displayed in different levels of grey. The differences in backscattering are determined by the geometry of the sensor-target system, the angle of incidence of the beam, the physical characteristics of the surface and the intrinsic nature of the surface (composition, density, relative importance of volume vs surface diffusion/scattering for the selected frequency (100-500 kHz). Highly fragmented habitats could clearly be detected using sidescan sonar by interpretating of their acoustic facies. The aim of this chapter is to describe the different techniques used in the geoprocessing of acoustic imagery for benthic habitats mapping and monitoring from a conservation perspective.