Algorithm 1. Pylon Body Parameter Estimation

Input:  matched horizontal 3D line segments of pylon body; fitted four pylon legs Output:  parameters of pylon body 1:Compute the maximum height $H_{\max }$ and minimum height $H_{\min }$ of the line segments 2:Generate the histogram of the height $H=H_{\max }-H_{\min }$ with a certain bin width $\Delta H$ 3:Group the line segments of which height locate in the same histogram bin 4:Find the maximum height of the group and regard its average height as the top horizontal rectangle height 5:Compute the total length of the groups of which height is in the range $(H_{\min },H_{\min }+\frac{1}{3}H)$ 6:Fine the maximum length of the group and regard its average height as the bottom horizontal rectangle height 7:Intersect the four pylon legs with the top and bottom horizontal rectangle height 8:Compute the height, position and direction of pylon body