Mapping Posidonia oceanica lower limit combining high resolution instruments (SSS and MBS)

High resolution Side Scan Sonar (SSS) combined with MultiBeam echo Sounder (MBS) was used for mapping Posidonia oceanica lower limit. For this purpose an acoustic survey was performed in Mondello Bay (Palermo, Italy) where a progressive lower limit of the seagrass occured. To improve the positioning precision of the SSS sonograms, data were joined by GIS platform and a repositioning process was performed. In particular, each sonogram was joined with the Digital Terrain Model (DTM) obtained by MBS, in which recognizable shapes of the sea-bottom were used as control points. After the repositioning process of the SSS data, the limit investigated during different periods showed a negligible error in absolute position, with an high level of spatial concordance compatible with the intrinsic error of the system.