Abstract: The complex terrain features and variable environmental conditions pose numerous challenges to the accuracy and efficiency of traditional terrain mapping methods. This paper proposes a complex mountain terrain modeling method that integrates 3D laser point cloud and BIM,aiming to enhance the accuracy,completeness and processing efficiency of terrain modeling. Firstly,the 3D laser point cloud data is preprocessed to ensure data quality and processing efficiency. Then,based on the geometric and semantic information of the BIM model,it is spatially aligned and information fused with the point cloud data to form a complete terrain and building integrated model. In the terrain reconstruction stage,the Delaunay triangulation algorithm is used to generate the initial terrain mesh,and the mesh is optimized by combining the building boundary information in the BIM model to ensure the spatial consistency and detail accuracy of the terrain model and buildings. Finally,the Laplacian smoothing algorithm is used to optimize the terrain surface to enhance the detail expressiveness of the model. The experimental results show that the proposed method significantly outperforms the traditional 3D point cloud method in terms of accuracy,with the average error reduced by 47%,the root mean square error (RMSE) reduced by 44%,and the maximum error reduced by 50%. At the same time,the modeling time is shortened by 75%,greatly improving the modeling efficiency,and shows higher detail accuracy at the junction of complex terrain and buildings. 

Key words: 3D laser scanning,BIM,Delaunay triangulation algorithm,terrain modeling,complex mountainous area