Towards a seamless integration for spatial objects and topography

In most spatial information systems, 3D topographic objects and geological strata are often represented as geometrically isolated models due to different data sources and different data models. Though current 3D representations can give satisfactory performances for visualization, the unlinked representations of spatial objects can hardly support real 3D spatial analysis, for instance the integrated simulation of building deformation caused by underground excavation and ground subsidence. In order to satisfy these specialized requirements, a seamlessly integrated geometrical model, which can connect topography with geo-objects both upon and below earth surface, is required. This paper presented such an integrated model which can couple 3D topographic objects and geological strata with the digital terrain model (DTM). The main implementation process of our integration approach is to model the terrain as triangular irregular network (TIN) firstly, with both discrete elevation points and drill collar points, and then insert the bottom triangles of buildings or other topographic objects into TIN as a DTM-coupled integrated model. This model has been adopted in a 3D modeling system called Geos3D@, with which an integrated model constructed from geological and topographical data in Shenyang, China is introduced as an application case.