Fig. 1. Absolute values of residual and the corresponding distance

Fig. 2. Tunnel segment

Fig. 3. Tunnel cross sections

Fig. 4. Ellipse fitting of (a) cross section 1 and (b) cross section 2

Fig. 5. Data filtering ( t =0.0074 m, σ =0.0212 m). (a) Original scanning data (7730 points); (b) filtering data (6497 points) with adaptive threshold t ; (c) filtering data (6924 points) with σ ; (d) filtering data (7179 points) with 2 σ ; (e) filtering data (7365 points) with 3 σ

Fig. 6. Deformation of tunnel section. (a) Elliptical cross section analysis; (b) circular arcs cross section analysis