Professor Christopher Gold has been active for over 30 years in the development of spatial data structures, spatial models of perception and adjacency, Geo-informatics applications, and algorithms. He has approximately 200 publications and presentations in many fields – GIS (Geographic Information Science), Computer Science, Geology, Forestry and others.He is known in the Geo-informatics community for his work on spatial data structures, Voronoi diagrams, dynamic mapping and 3D modelling.
He is known within the Computational Geometry community for his work on GIS applications. He has been active in Mathematics conferences, in Geology and Engineering workshops, and in Forestry. He has made presentations or organized workshops in Canada, USA, Europe and China. He has received a variety of honours from Canadian and Asian associations, and he has collaborated with a wide variety of researchers in Europe, North America and Asia. He has supervised approximately 20 research students and research assistants. He has had particularly strong research collaboration with China, having been involved with researchers there for fifteen years.In 1990 he was appointed the Senior Researcher of an Industrial Research Chair funded by the Quebec Forest Industry and the Canadian National Science and Engineering Research Council (NSERC).From 2000-2004 he was Professor and Research Director, Land Surveying Dept., Hong Kong Polytechnic University.From 2004-2007 Prof. Gold held the post of “EU Marie Curie Chair” with the GIS Research Group at the University of Glamorgan.
Title of Talk: The Dual is the Context: Spatial Structures for GIS
GIS (Geographic Information Systems) are concerned with the manipulation and analysis of spatial data at a “Geographic” scale. Apart from issues of storage, database query and visualization, they must deal with several significantly different types of spatial information. These may be roughly classified as: discrete objects; networks; polygonal maps; and surfaces. Each of these has a specific set of assumptions associated with it, a specific data structure, and a specific set of algorithms. This produces a high level of complexity in the construction, manipulation, analysis and comparison of these datasets. We demonstrate that when “here” is replaced by “closest to here” the resulting proximal query (a Voronoi diagram) may be used to manipulate the four categories described above, with a resulting simplification of the system. All discrete objects become “fields”, with a value at any location. These fields provide the ‘context’ of the object, and many applications require both the primal and dual for analysis: the Quad-Edge is therefore the data structure of choice.
Thus in 2D the ‘context’ – the dual set of adjacent neighbours and neighbourhoods, as identified by the Voronoi diagram – greatly assists in the interpretation and analysis of the data. In 3D the same thing holds true: the dual graph of the 3D object set – in 3D GIS perhaps a model of the rooms of a building interior – gives a clear structure for expressing their adjacency relations. A direct modification of the Quad-Edge – splitting the four parts into two pairs, each containing one primal and one dual half-edge – provides a structure appropriate for CAD-type non-manifold modelling, which we demonstrate by the construction of a large building complex, using Euler-type operators. Thus, again, the dual graph provides the context for the (primal) geometric data.