POSITION ESTIMATION FOR AN AUTONOMOUS MOBILE ROBOT IN AN OUTDOOR ENVIRONMENT

This paper presents a solution to the position estimation problem of an autonomous land vehicle navigating in an unstructured mountainous terrain. A digital elevation map (DEM) of the area in which the robot is to navigate is assumed to be given. It is also assumed that the robot is equipped with a camera that can be panned and tilted, a compass, and an altimeter. No recognizable landmarks are assumed to be present in the environment in which the robot is to navigate, and the robot is not assumed to have an initial estimate of its position. The solution presented here makes use of the DEM information, and structures the problem as a constrained search paradigm by searching the DEM for the possible robot location. The shape and position of the horizon line in the image plane and the known camera geometry of the perspective projection are used as parameters to search the DEM. Geometric constraints are used to prune the search space significantly. The algorithm is made robust to errors in the imaging process by accounting for worst case errors. The approach is tested using real terrain data of areas in Colorado and Texas. The method is suitable for use in outdoor mobile robots and planetary rovers.