High resolution with small budget. The “GeoDive” method for detailed 3D reconstruction of submerged morphologies and related measurements

The most widespread acquisition methods for lakes and sea bottom geological data are ship-, ROV- or AUV-based; geophysical methods and the related instruments for morpho-bathymetric survey allow to characterize large areas, even at high depths, but with high costs. It is known that shallow waters can represent a limit for certain vessels and techniques, preventing the acquisition in the nearshore zone. To overcome the limits, i.e. to survey with high accuracy nearshore shallow waters with a low budget, we tested and tuned the “GeoDive” method that allowed us to survey two test sites, featured by the presence of “block fields” (i.e., accumulations of huge blocks and boulders of gravitational origin) under shallow waters. The “GeoDive” allowed us to map the submerged morphologies and to acquire high-resolution optical images for further photogrammetric processing. The latter was fundamental to obtain 3D high-resolution models, also with conditions of low visibility. An Action Sport Cam (ASC) HD has been used for video acquisition, in addition to the equipment used during scientific diving. By coupling the processed underwater-acquired data with the direct surveys performed by underwater SCUBA operators, it was possible to perform some morphological and sedimentological measurements and observations on the experimental targets, with the help of suitable markers