Abstract
In this paper, I review the development of three-dimensional geographic information systems (GISs) and demonstrate how we can move beyond this to extend GIS to virtual reality. Existing elements of GIS which can imply three-dimensional representation, namely two-dimensional representation, digital elevation modeling, and visualization techniques, are first reviewed. Then it is argued that new techniques in multimedia, three-dimensional modeling and virtual reality are now at the point where they might be embodied in GIS. However, to do this, a true three-dimensional GIS must enable the following functions: realistic representation of the third dimension in data and in visualization, free movement of the user within the three-dimensional representation, normal GIS functions such as query, overlay, etc, but within three-dimensional data space, and visibility functions such as line of sight and related requirements. These ideas are then illustrated with several demonstrations being developed using new generations of high memory workstation.
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