Research On Unified Expression Method Of Urban Multi-source 3D Model Data

With the development of oblique photogrammetry technology and laser scanning technology,3D model data such as oblique photogrammetry model,3D LIDAR point cloud and fine building model have become important data sources in digital city,urban planning and emergency services.Domestic and foreign scholars have carried out extensive research on many aspects such as data organization,indexing and visualization of 3D models.However,most of the current researches on 3D model data are the organization and visualization of single type data or single scene,which is not conducive to multi-scale visualization and analysis under different requirements.In practical applications,a single type of data often cannot meet the application requirements of complex scenarios,and multiple 3D model data needs to be used together.At the same time,the requirements of the visualization and analysis of the 3D model on the accuracy of the data are determined by the scale at which it is located,and the correspondence between the scale and the accuracy of the 3D model data needs to be established.Therefore,how to design a unified method for the organization and expression of 3D model data needs further study.Based on the research of the current mainstream 3D model data organization method,geographical grid and map service specification,this paper proposes a unified expression of multi-source 3D model data for the unified organization and expression of 3D model data.Based on this method,an interactive visualization method for multi-source 3D model data is designed.The main contents of the paper are as follows:(1)Research on unified expression method of multi-source 3D model data.A unified organization method of multi-source 3D model data based on geographical grid is proposed.The geometrical and scale features of the 3D model data are analyzed,and the datum geographical grid model is designed.Based on the model,a unified division and coding method suitable for multi-scale 3D model data is constructed to realize the unified organization of multisource 3D model data.A unified description rule for the structural expression of 3D model information is designed,which realizes the structured expression of the geometry,appearance and attributes of the multi-source 3D model data.(2)Research on interactive visualization methods for multi-source 3D model data.Based on the unified expression of data,construct a compound pyramid model for urban 3D scene visualization to realize rapid visualization of urban 3D scenes.Analyze the scale features of urban 3D scenes,and realize the interactive visualization of multi-source 3D model data by designing the relevant interfaces of the compound pyramid model and spatial semantics(attribute type,spatial range,spatial scale)rules.(3)Aiming at the above research content,based on the WebGL 3D rendering engine,a practical three-dimensional unified expression system for urban scenes was developed to verify the validity and feasibility of the unified expression method of multi-source 3D model data.