Multi-resolution 3D Terrain Modeling Of Sea-Land Integration

The topography of land and seabed is an important part of natural resource monitoring.At the same time,it is also an indispensable basic geographical element for coastal city planning and ecological environmental protection.Realizing the integrated sea land 3D terrain modeling is of great significance for the land-sea coordination of natural resource monitoring and national land spatial planning.At present,the modeling of terrain is mainly implemented by irregular triangulation TIN,but the traditional TIN-based multi-resolution expression method has many problems,such as the data redundancy and discontinuities in scale transition.In order to solve these problems,this paper proposes a multi-resolution 3D modeling method based on detail-incremental model,which is applied to the construction and visualization of terrain model of sea-land data.The main work of this study is as follows:(1)Sea-land data integration and parallel construction.At first,this paper preprocesses and merges the multi-beam terrain data of seabed and the laser point cloud data of land,to obtains the integrated 3D point cloud data.And then the final point cloud is segmented by the adaptive quadtree method,so that the sub block size and points are within the required range,and the adaptive block based on the points'density is realized.At the same time,with the help of OpenMP's CPU parallel technology,the point data in the sub-blocks are constructed based on their convex hulls to obtain the initial integrated land-sea terrain model;(2)Multi-resolution terrain construction based on detail-incremental model.According to the quadric error metric(QEM),the complex terrain base model in each sub block is processed by edge collapse based on the detail-increment model,the triangle changed in each simplification process is stored as the detail increment information,and the final simplified terrain mesh becomes the most simplified model.With the help of the most simplified model and a series of incremental information,the simplification and refinement of any scale of terrain can be realized;(3)Multi-resolution 3D progressive expression.By taking the mean minimum quadric error(MMQE)of each scale as the smallest visible object(SVO),combining the sub-blocks of the quadtree and the multi-resolution structure of the detail-incremental model,the changes of model details adapted to the human eye identification are realized,and the progressive expression of the sea-land integrated multi-resolution 3D model is finally completed.In this paper,the above theories and methods are verified by using the land and seabed terrain data of Yanzhi Island in Xisha,based on C++,OpenGL and QT.for experiment and analysis.The final experimental results show that compared with the traditional method,the triangulation algorithm in this paper can improve the efficiency by more than one time,and the number of frames in the progressive expression can be kept above 25,which can meet the requirements of interaction fluency.And compared with the traditional static multi-resolution expression,the method in this paper has lower data redundancy,more delicate level details and more accurate progressive expression effect.The research results of this paper have been integrated into the seabed topography post-processing system.