The 3D modelling techniques of digital geological mapping

Abstract

Digital geological mapping has been widely applied in regional geological surveying in China since 2004. Using geological mapping data obtained by the digital geological mapping technique to build 3D geological modelling is the trend of the future. Based on previous research, a new method of constructing 3D geological models of shallow surfaces by using digital geological mapping routes and topographic data is proposed in this paper. The key steps of this modelling method are described systematically in the paper. These steps include data pre-processing, construction of an original database, construction of geological boundaries, and model combination. In particular, we introduce in detail the model construction methodologies of the model boundary surface, digital elevation model (DEM) surface, Quaternary interface, fault plane, overlying residual stratum interface, layered geological interface, rock mass interface, and others. During the geological interface construction, we should follow two principles: (1) use the boundary and occurrence data as the main modelling data, and use the high-precision subsurface interface data as constraint data; (2) construct younger geological bodies first, and then construct older geological bodies. The next step is to compose sectionalised geological interfaces and use them to generate a geological interface of wider range. The interface construction progresses from small to large and is constantly constrained and continuously improved. Based on this new modelling method, we successfully constructed two 3D geological models, the 1:25,000 Xiaosuangou and the 1:50,000 Tuoshang models, and achieved good results. This modelling method has the advantages of simple realisation, high speed, high accuracy, and good applicability. Using this method to build 3D geological models can facilitate further development and utilisation of existing digital geological mapping data. The 3D geological models can be used as a new way of expressing the regional geological survey results, as well as the constraint data of deep 3D geological modelling in the future.