A Digital Urban Space Model - - - - A Three Dimensional modelling technique of Urban Space in a GIS Environment

Conventional two dimensional(2D) maps and DTMs are insufficient to represent geographic information in urban space comprising high-rise buildings and underground structures. There is a pressing need for a model of three dimensional(3D) representation of urban space, that is, a Digital Urban Space Model(DUSM). However, existing solid modelling techniques cannot be directly applied to the 3D representation due to several problems such as the inefficiency in building and updating 3D spatial database. Based on the boundary representation(BR) model, the authors proposed a Surface Represetntation(SR) model which can greatly improve the efficiency in building and updating 3D spatial database. Through an example of the 3D representation of urban space, it is demonstrated that the SR model incorporated with an elevation interpolation method can be succussfullyapplied. Keywords;" three dimensional(3D) representation, Solid modelling method, Urban space, Boundary Representation(BR) model, Surface Representation, Elevation interpolation