The invention relates to the field of measurement, in particular to a subway tunnel secondary lining section limit measurement method based on SLAM mobile scanning, which comprises the following steps: step 1, tunnel
point cloud acquisition and target clustering
point cloud acquisition; step 2, CPIII
control point coordinate extraction; step 3,
point cloud coordinate conversion; 4, performing
point cloud processing, and removing noisy points and non-secondary-lining target point
cloud data in the tunnel secondary-lining point cloud; and step 5, performing three-dimensional limit deviation analysis, performing spatial comparative analysis on the point cloud under the construction coordinate
system and the subway secondary lining tunnel design three-dimensional model by adopting a voxelization deviation
mapping algorithm, extracting a continuous deviation region through
voxel clustering, and generating a three-dimensional deviation thermodynamic diagram. According to the method, the two-lining tunnel point cloud obtained by SLAM mobile scanning is accurately converted into a construction coordinate
system by combining CPIII high-precision control points in the tunnel, rapid, visual and three-dimensional contrastive analysis with design of a three-dimensional model can be achieved, and visual and reliable data support is provided for line and slope adjustment, track laying and defect improvement.