Algorithm 1. Converting the 2D mesh to a tunnel-shaped mesh

Input: raw point cloud R (x, y, z); meshed plane point cloud P (x, y, 2.75)

Output: tunnel-shaped mesh T (x, y, z)

1: R (θ, y, ρ) ← Switch Cartesian coordinates R (x, y, z) to polar coordinates

2: P′ (x′, y′, z′) ← Roll up the plane data P (x, y, 2.75) to cylindrical data

3: P″ (θ″, y″, ρ″) ← Switch Cartesian coordinates P′ (x′, y′, z′) to polar

4: for each point P″i (θ″i, y″i, ρ″i) do

5:    Extract the set Nk (θ, y, ρ) from R (θ, y, ρ) ← k nearest neighbors of θ″i where | y″i − y | < m

6:    Compute the average ρki from Nk (θ, y, ρ)

7:    Ti (xi, yi, zi) ← Switch polar coordinates (θ″i, y″i, ρki) to Cartesian coordinates

8: end for

9: return T