THE IMPLICIT TRIANGULATED IRREGULAR NETWORK AND MULTISCALE SPATIAL DATABASES

The triangulated irregular network (TIN) provides a versatile and wide ly used approach to representing terrain models in a way that retains the original sample points, adapts to variation in data density and in corporates linear features corresponding to natural or man-made phenom ena. Classification of the scale-related priority of the constituent p oints and linear features can be used to create hierarchical, multires olution TIN representations. A large proportion of the data items incl uded in conventional and hierarchical TIN data structures are concerne d with recording the topology of the triangulation. Although TINs typi cally use many fewer points than the main alternative representation o f regular rectangular grids, they do not usually occupy much less data storage, due to the topological data. This paper describes a novel mu ltiresolution storage scheme which uses an approach termed the Implici t TIN, in which storage requirements are reduced significantly by stor ing only the vertices and constraining features. TIN topology is recon structed by a procedure when required. The Implicit TIN storage scheme has been demonstrated in the context of an experimental multiscale da tabase. Variable-scale access is provided to polygonal regions of a te rrain model which includes polygon, line and point objects that constr ain the constructed triangulated model.