METHOD FOR FINDING IMPORTANT CHANGES IN 3D POINT CLOUDS

A motion detector comprising a sensor apparatus and a calculator arranged for: generating first and second successive frames comprising each a 3-D cloud of points, wherein each point represents a position in space of a surface of at least an object in the field of vision of said sensor apparatus; transforming each of the first and second frames by: mapping each cloud of 3-D points into a 2-D grid of cells associated each to a sequence of predetermined volumes; and associating to each cell of the 2-D grid of cells a sequence of the lists of the points contained in corresponding volumes of the sequence of predetermined volumes; comparing the sequences of lists associated to the same cells of the 2-D grids obtained for the first and second frames; and indicating that motion occurred based on the sequence of lists being different in the first and second frames.