A novel approach to location estimation by omni-directional vision for autonomous vehicle navigation in indoor environments using circular landmark information is proposed. A circular-shaped landmark is attached on a ceiling and an omni-directional camera is equipped on a vehicle to take upward-looking omni-directional images of the landmark. This way of image taking reduces possible landmark shape occlusion and image noise creation, which come from the existence of nearby objects or humans surrounding the vehicle. It is shown that the perspective shape of the circular landmark in the omni-directional image may be approximated by an ellipse by analytic formulas with good shape-fitting effect and fast computation speed. The parameters of the ellipse are then used for estimating the location of the vehicle with good precision for navigation guidance. Both simulated and real images were tested and good experimental results confirm the feasibility of the proposed approach.
