Fig. 4

Illustration of the process of tracing a real arc in its image. The left panel shows the five p points used to compute the arc length. The right panel shows the high-intensity m points (dashed circles) used to find pmax for the same arc. The center and radius of curvature are determined as the circle containing the points p1,p2, and pmax = m2. The width is based on the line through the central point p3, whereas the asymmetric major-axes a1 and a2 are the lengths of the segments connecting m2 = pmax to the arc extremes p1 and p2.
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