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Histogram of the cross sections’ dimensions: (a) The histogram of semi-major axis; (b) The histogram of semi-minor axis; (c) The histogram of area; (d) The histogram of eccentricity. The histogram bin width of the axes, area, and eccentricity is 0.01 m, 0.1 m, and 0.01 (unit-less), respectively. The bin widths are selected with respect to the dataset point sampling, the tunnel’s dimensions and the employed LiDAR sensor specifications.
