Research On Regional Integrated Automatic 3D Geological Modelling Based On Topological Relationship

The 1:5 million and 1:25 million regional three-dimensional geological mapping is the main task of digitizing China’s basic geological survey and shifting it from 2D to 3D.At present,the domestic and international 3D geological modelling software is insufficient in process automation and consistent topology integration of the regional 3D geological modelling.Based on the PRB data of regional digital geological survey,this paper integrates modelling methods suitable for various types of geological structures and automatically constructs 3D models.The following are the main research contents:(1)Explicit and implicit integration modelling methods for various types of geological structures.Through the analysis of the characteristics of different geological structures such as inclined strata,folds,faults,volcanic bodies and Quaternary,according to the geometry of the structure,modelling constraints and data source features,etc.,the skinning method,Coons surface method and Hermite Radial Basis Function(HRBF)methods were introduced separately.The moving tetrahedral visualization technology was adopted,and the method of converting explicit surfaces into implicit surfaces was proposed to solve the problem of difficult geometric integration and 3D visualization between different geological body models in regional geological modelling.(2)Geological structure contact relationship analysis and geological boundary organization method.The geological boundary of adjacent geological structures is a direct data source for calculating the HRBF implicit function surface.Based on the geological age and topological relationship,this paper analyzes the contact relationship between various strata and rock mass,defines the concept of arc segment order,and proposes the automatic organization method of geological boundary.(3)Automatic modelling method for geological objects.Considering the factors such as the coverage relationship and developmental age of geological structures in implicit cutting modelling,it is difficult to automatically form a clear cutting modelling sequence based on geological boundaries.However,geological objects have a clear geological age,based on which it is convenient to calculate the modelling order.Therefore,for the problem of difficult to organize geological boundary cutting sequences,based on the feature structure adaptive modelling method,an automatic modelling method for geological objects is proposed.Based on the above research contents,a prototype system for regional automatic 3D geological modelling was designed and developed,and experiments were carried out with actual data of regional geological maps at home and abroad.The modelling results and comparative analysis show that:(1)The explicit and implicit integrated modelling methods proposed in this paper can guarantee the topological consistency of the regional geological body model;(2)Compared with the implicit modelling method based on geological boundary cutting sequence,the modelling method for geological objects is superior in maintaining topological relations and promoting modelling automation.