Fig. 1. Overall structure of SSW vehicle-borne laser modeling system

Fig. 2. Common manhole cover disease problems.(a) Manhole cover sinking; (b) manhole cover raised

Fig. 3. Flow chart of rapid identification and location of manhole cover and disease detection technology

Fig. 4. Schematic diagram of two-point tilt diagram

Fig. 5. Principle diagram of CSF algorithm

Fig. 6. Image binarization results of global threshold and adaptive threshold. (a) Sample image 1; (b) sample image 2

Fig. 7. Frame diagram of precise extraction of manhole cover

Fig. 8. Schematic diagram of edge curvature. (a) Round edge contour of manhole cover; (b) arc differential; (c) curvature

Fig. 9. Manhole cover extraction and marking

Fig. 10. Rigel laser scanner

Fig. 11. Experimental point cloud data. (a) Experimental data point cloud roadmap; (b) coloring map of pavement point cloud intensity

Fig. 12. Combined ground filtering. (a) Ground points; (b) non-ground points; (c) combination of ground points and non-ground points

Fig. 13. Automatic extraction of urban manhole covers based on vehicle-borne laser point cloud. (a) Original point cloud (real scene rendering); (b) ground points (intensity coloring); (c) intensity feature image; (d) manhole cover extraction result; (e) partial enlarged view

Fig. 14. Manhole cover extraction result. (a) Schematic diagram of manhole cover position 1; (b) schematic diagram of manhole cover position 2