Towards an integrated three-dimensional geographic information system

To date, little theory and few geographic information systems (GIS) have been developed to handle geographic phenomena in true three-dimensional (3-D) geometry and topology. This thesis presents an approach to the development of fundamental principles and techniques for modelling and analyzing geographic phenomena in an integrated 3-D GIS. The work includes development of a 3-D topological-vector Delaunay tetrahedral data model and development of efficient algorithms and functional components for modelling and analyzing 3-D geographic information.; Logical components of the 3-D Delaunay tetrahedral data model are defined in terms of spatial entities, spatial objects, and spatial primitives for modelling 3-D geographic phenomena. The model not only defines the geometric elements, but also identifies the spatial relationships among them. A relational database approach is adapted for structuring both spatial and nonspatial information. Furthermore, a Delaunay-based Convex Hull Insertion (CHI) algorithm is developed to efficiently construct the 3-D Delaunay tetrahedral data model. By introducing constraint and boundary surfaces into 3-D Delaunay tetrahedral tessellations, an integrated 3-D GIS model is developed for handling complex geographic phenomena in 3-D space. The 3-D Delaunay tetrahedral data model also maintains downward compatibility to modelling geographic phenomena in a two-dimensional (2-D) plane. However, 3-D surfaces, volumes, associated spatial relationships, and other 3-D spatial analysis functions are not applicable to planar data.; Fundamental 3-D GIS functions concerning data manipulation and spatial analysis based on the Delaunay tetrahedral data model are stressed in six selected categories: (1) measurement; (2) 2-D overlay; (3) 3-D overlay; (4) surface analysis; (5) volume analysis; and (6) Voronoi tessellations. Among these functions, the 3-D overlay operations are highlighted as building blocks for compound and advanced operations for handling geographic information in true 3-D geometry and topology. Other selected supporting functions in data entry and verification, data storage and data management, and data output and presentation are also developed to enhance the functional framework of the integrated 3-D GIS.