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The opening positioning for railway oil tank wagon using machine vision technology is an effective way to load petroleum automatically. To overcome the adverse effects produced by illumination changes, various types of railway tank wagon and various positions of camera, a shape matching positioning method is proposed in this paper. Due to the shape of the opening of railway tank wagon is a standard geometry, the edge of the opening can be extracted from a standard image so that the shape of the opening can be described by shape fitting method, which is used as standard template of image recognition, then contour normalized correlation is employed to search the object in the image. To improve flexibility, scalable template is used so that various types opening image of railway tank wagon can be processed by the proposed method. To gain a speed-up, image pyramid is applied to reduce calculation amount. The experiments show that the proposed method fully meets the requirements of practical industrial applications. Index Terms -vision positioning, shape matching, railway oil tank wagon, big crane tube, machine vision