Spherical projection triangulation algorithm for laser-scanning splice unorganized points of complex goafs

Detection of a goaf by laser-scan technology to build a 3D visualized model and to obtain the goaf's 3D space position and shape, is an important part for comprehensive management of the goaf's accidents. Multiple probes from multiple orientations are usually needed to obtain a goaf's 3D shape because of its complexity. How to construct a triangular mesh model from splice unorganized points by multiple probes is the key technology of a goaf's 3D modeling. A spherical projection triangulation algorithm is proposed for laser-scanning splice unorganized points of a goaf in this paper. Firstly, projected points are got by a chosen sphere center and projecting in-situ points onto the sphere. Secondly, the projected points are triangularized completely. Then topological relations are reverted from the projected points to the in-situ points. At last, a triangular mesh model of the goaf is constructed. In order to effectively implement the algorithm, many methods are studied such as the spherical projection parameters setting, XYZ-orientation cell grid points searching strategy, triangle generation rules, boundary segment strategy by advantage vertexes, boundary closure strategy, and irregular triangle optimization strategy. Applications show that the algorithm can generate a high quality triangular mesh model and provide technical support for accurate 3D modeling and visualized management of a goaf.