The invention concerns an apparatus for measuring the three-dimensional (3-D) sea surface elevation from moving and floating platforms. In particular, the invention consists of two or more synchronized digital video-cameras that frame, from distinct and remote points of view, a common portion of the sea surface. A triangulation process makes it possible to obtain a three-dimensional reconstruction of the sea surface from these images. The invention is particularly suitable for measuring sea waves. The apparatus is equipped with IT procedures for the automatic calculation of the mutual position of the cameras and the roto-translation between the cameras and the mean sea level. The stereo cameras are also interfaced with an instrument (Inertial Motion Unit, IMU, and Global Positioning System, GPS) for the measurement over time of the 6 degrees of freedom (3 rotations and 3 translations) which completely define the instantaneous rigid motion of the vessel (subject to waves and therefore moving in the 3-D space). The invention is accompanied by 3-D data analysis techniques that improve the accuracy of movement correction. The invention is particularly suitable for the collection of scientific data in different sea states from research or ships of opportunity, as well as being used by vessels for "operational" knowledge of the sea state. The latter data can increase the safety of navigation and operations on board.
The instrument allows the accurate measurement of the sea states (surface waves) by using stereo cameras achievable at a low cost. It is particularly designed for the wave characterization from moving ships or any other floating structure, whose operativity depends on the sea state characteristics (e.g., wind turbines). Its features make the instrument also easily deployable in locations where the human access is difficult (e.g. lighthouses).
Italy