Recursive surface structure recognition for safe navigation

Methods for extracting in real time the surface structure in a certain look-ahead range from image sequences while driving are reviewed. Low spatial frequency elevation profiles of roads are the only ones successfully recovered in real-time up to now. Low frequency means that the characteristic geometrical dimension for curvature estimation is at least an order of magnitude larger than the axle distance of the vehicle carrying the camera. For the more general case of a surface with relatively high spatial frequencies an approach for real-time recognition is proposed which separates low, medium and high spatial frequency components; these components are estimated in a sequential, iteratively parallel manner. The formulation of the approach is given