A Skeleton-Line-Based Spiral Coverage Path Planning Method for UAV Inspection of Three-Dimensional Structures

Abstract

UAV-based visual inspection has become an effective approach for acquiring surface information from three-dimensional building structures. However, existing coverage path planning methods usually treat viewpoint planning and path sequencing as two separate stages, which may introduce redundant viewpoints, long connection paths, and high computational cost. To address this problem, this paper proposes a skeleton-guided spiral coverage path planning method for UAV inspection of 3D structures. The target building model is first converted into a watertight triangular mesh, from which a one-dimensional skeleton line is extracted to guide both viewpoint generation and path construction. Surface sampling points are generated using rotating radial rays along the skeleton line, and UAV viewpoints are obtained by offsetting these points according to a predefined viewing distance. The ordered viewpoints are then connected to construct spiral coverage paths, while visibility checking, safety-distance constraints, and collision detection are incorporated to ensure path feasibility. Parameter sensitivity analysis shows that the sampling interval has a dominant influence on coverage performance and path cost, while the angular increment mainly affects path compactness and construction efficiency. Comparative experiments on the Christ, Wind Turbine, and Big Ben models demonstrate that the proposed method achieves high coverage rates of 96.62%, 97.72%, and 99.67%, respectively, while generating shorter paths and requiring substantially less computation time than ACO−OPD and Zhao’s method. These simulation results indicate that the proposed method can generate compact coverage paths with substantially lower computation time for UAV coverage inspection of 3D structures.