3D SPATIAL DATA MODEL BASED ON QUASI TRI-PRISM VOLUME AND ITS APPLICATION IN SUBSURFACE ENGINEERING

3D spatial data model and modelling are the core of 3D GIS theory and applications. For this reason, a data model based on Quasi Tri-Prism Volume (QTPV) has been presented in this paper. The QTPV definition and its special cases due to vertices of QTPV may be superposition have been considered. The proposed model is composed of five primitives and six objects. The primitives consist of vertex, segment (edge, triangle side), triangle, side quadrilateral, and QTPV, and the objects consist of point, line, face, solid, complex, and spatial object. Their data structures and topology describing stratigraphy are designed and implemented in detail. Some modelling methods are designed for the purposes of the QTPV modelling of stratigraphy and subsurface engineering according to the modelling data. The model manipulation for the QTPV cutting using an arbitrary plane is discussed. We implemented a system prototype, called 3DGeoMV, using VC++6.0 programming language integrated with SQL database and OpenGL graphic library under the windows environment. The real data from the boreholes, which located at a geological exploration area in China’s Inner Mongolia, is used to verify the developed model and the developed system prototype. The experiment result demonstrates that the QTPV model is feasible and efficient for applications in the subsurface engineering. With applications of the presented QTPV, irregular natural geological bodies and/or regular subsurface engineering can be represented efficiently