The paper presents the self-localization approach used by the World Champion in the Sony Four-Legged Robot League 2004. The method is based on a particle filter that makes use of different features from the environment (beacons, goals, field lines, field wall) that provide different kinds of localization information and that are recognized with different frequencies. In addition, it is discussed how the vision system acquires these features, especially, how the orientation of field lines is determined at low computational costs.