VisAGGE: Visible angle grid for glass environments

We describe a new algorithm for occupancy grid mapping using LIDAR in the presence of glass and other non-diffuse surfaces. This is a major problem for robot navigation in many indoor environments due to the prevalence of glass paned doors, windows, and even glass walls, as well as mirrors and polished metal surfaces. Current formulations of occupancy grid mapping make the assumption that objects in the environment are detectable from all angles. However, glass and other specular surfaces are invisible to LIDAR at most angles and so become washed out as "noise". We modify the standard occupancy grid algorithm to allow for mapping objects that are only visible from certain view angles, by tracking the subset of angles from which objects are reliably visible. We show that these angles can be determined reliably with a single pass through the environment, and that the information can be used to map both diffuse and specular surfaces.