Concrete Spalling Detection for Metro Tunnel from Point Cloud Based on Roughness Descriptor

Table 1

General information of the case area and data collection.

Parameters	Value
Length of case tunnel	250 m
Radius of the tunnel	2.75 m
Average velocity during data collection	0.5 m/s
Scanning distance	330 m
Scanning range	300°
Working frequency	100 Hz
Resolution	1/4
Range error ()	2 mm
Vertical point spacing ()	2 mm
Longitudinal point spacing ()	5 mm
Point density	100,000 pts/m^2
Total points	> 500,000,000 pts