Abstract: To solve the problems of positioning failure and accuracy reduction caused by skewedness and nonstandard
size of images in the track image, a fastener positioning algorithm based on the spike center point location and
geometric structure features was proposed. The new method adopted the idea of first locating the center point of the
spike, and then locating the fasteners with geometric features. Based on the edge image obtained by image
preprocessing, the edges of track spike in the image would be characteristic of roundness after being corroded and
dilated. Then, by means of the Hough transform circle detection algorithm, the rough area of the spike was located and
expanded, so that the spike area could be roughly extracted from the original image. The edges of spike area image
were then detected and OpenCV, a contour extraction and polygon detection algorithm, was employed to accurately fit
the spike hexagon and calculate the spike center point. Finally, the coordinates of each vertex of the fastener bounding
box was obtained using the fastener location algorithm proposed based on geometric structure features. The
experiment results show that the positioning accuracy of the new algorithm is 99.33%, the precision is 0.997, and the
speed is 29.8 fps, superior to the algorithms compared. Meanwhile, under different circumstances, such as weather
conditions, spike corrosion, or occlusion, the new algorithm displays better robustness and anti-interference ability.

Key words: fastener positioning, spike positioning, contour extraction, polygon detection, geometric features