A novel algorithm for reconstructing 3-D road geometry from images is presented for the purpose of autonomously navigating land vehicles. The reconstruction is based on an idealized road model: a road is assumed to be generated by a horizontal line segment of a fixed length sweeping in the scene. The constraints that ideal road images must satisfy are expressed as a set of differential equations; the 3-D road geometry is reconstructed by numerically integrating these equations. In order to prevent numerical instability, a correction scheme is proposed for stabilizing computation: at each numerical integration step, the computed solution is modified in such a way that the required constraint is always satisfied. Some examples based on real road images are shown. The inherent ill-posedness of the problem and related technical issues are discussed in detail. >
['Kenichi Kanatani', 'Kazunari Watanabe']
Reconstruction of 3-D road geometry from images for autonomous land vehicles