Environment modeling for topological navigation using visual landmarks and range data

This article describes the integration in a whole navigation system of visual functions dedicated to the extraction and recognition of visual landmarks, i.e. planar quadrangles detected from a single camera. The extraction of these landmarks is based on a relaxation scheme, used to satisfy constraints between image segments. During the exploration of an indoor environment, according to the current topology, there are several ways to take advantage of these visual landmarks. Two representations are considered, relying both on laser data and or our visual landmarks system: a GVG-based model (generalized Voronoi graph) for corridors, and a composite stochastic map for open spaces. In the particular case of corridors, the corresponding modules - laser GVG construction and visual landmarks extraction and recognition - can cooperate to complete each other, as image processing can be enhanced by some structural knowledge about the scene, whereas the GVG is annotated, even as far as its edges are concerned, by qualitative visual information.