Analysis of the influence of range and angle of incidence of terrestrial laser scanning measurements on tunnel inspection

• We propose a methodology to build an error model of the TLS measurements.
• The angle of incidence has great influence on the point cloud quality.
• TLS position influences the quality of the point cloud.
• A high density of points compensates for errors produced by the scanner position.

Terrestrial Laser Scanner (TLS) measurements are subject to errors which influence the quality of the 3D models built from the point clouds. In this paper, a methodology to build an error model of the TLS measurements is proposed. Measurement errors are estimated based on two of the factors that mostly affect their magnitude: distance to the object and angle of incidence.The error model is used to analyze, by means of Monte Carlo simulation, the spatial distribution of the errors in a point cloud of a circular tunnel section and also to simulate the effect of the measurement error in tunnel inspection works.The results obtained indicate that although the angle of incidence influences the point cloud quality when the laser is located near the tunnel gable, its effect is counteracted by the point density when a surface is fitted to the point cloud.

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