Transformation Method For Automatic Generation Of Buildings In CityGML LOD1-LOD4 Using IFC Models

One of the basic signs of upgrading from digital city to smart city is the refinement of urban management,the integration of indoor,outdoor,underground and underground space has been put forward the unprecedented demand.The three-dimensional environment of city is very complex,the current mapping methods include tilting photogrammetry,laser scanning and traditional mapping are difficult to effectively obtain the three-dimensional structure of the building indoor,compared with outdoor information,the indoor information of 3D GIS is still extremely short,it is difficult to meet the growing demand of application.In recent years,the development of BIM technology is rapid,BIM model has high degree of fine,characteristic parameterization,rich semantic information and the description of indoor information is very fine.The accurate indoor information of BIM model can be used as an important data source for 3D GIS.In this paper,based on the key technical problems of BIM and GIS data integration,the IFC standard of BIM field and the CityGML standard of three-dimensional GIS field is selected,the method of extracting multi-detail hierarchical GIS surface model from BIM entity model is designed.The main contents of this paper are as follows:1.Firstly,this paper introduces the research background and significance and summarizes the research status and development trend of BIM and GIS integration and IFC and CityGML mapping extraction at home and abroad.It puts forward the research purpose and research content of this paper,and expounds the significance of this study.2.Because of the difference of geometry,semantic and structure of the IFC standard and the CityGML standard.The IFC and the CityGML data mapping key technical challenge has to be discussed.3.According to the different description of IFC and CityGML to the building elements,the semantic mapping relation between IFC and CityGML LOD1-LOD4 is established,based on the the semantic mapping,semantic filtering is used to model the IFC model.Aiming at the huge difference of the geometry of IFC and CityGML,the geometric reconstruction algorithm is designed to reconstruct the geometry of the IFC model into geometry defined in the CityGML standard.According to the organization of building elements of the CityGML standard,the geometric and semantic information of the single building component extracted from the IFC model is need to be reorganized,at the same time the coordinate conversion algorithm of CityGML LOD4 to CityGML LOD1-LOD3 is to be designed.4.Based on the CityGML ADE,semantic information is extended,the attribute and floor information extracted from the IFC model is extended to the CityGML model.