Context: Biocenosis mapping basically requires 2 types of data:
• “extrapolation” data obtained from multi- and single-beam echosounders, side-scan sonar, interferometric sonar, aerial images, etc., covering the entire study zone.
• “sea-truth” data obtained from ROV, trawl cameras, deep-sea diving, etc., which consist of direct but irregular observation of biocenoses.
The sea-truth phase is often neglected; when it is done with a trawl camera or ROV the data are much less reliable than those obtained by a biologist diver (problems with lighting, viewpoint, etc.).
Scope: To improve the results of the sea-truth phase, we developed the audio-diver, a transect system which enables the diver biologist in communication and exactly positioned by GPS to validate the terrain by transects of several thousand points long extending up to ten or so kilometres a day.