Abstract
Abstract. Different users or applications need different scale model especially in computer application such as game visualization and GIS modelling. Some issues has been raised on fulfilling GIS requirement of retaining the details while minimizing the redundancy of the scale datasets. Previous researchers suggested and attempted to add another dimension such as scale or/and time into a 3D model, but the implementation of scale dimension faces some problems due to the limitations and availability of data structures and data models. Nowadays, various data structures and data models have been proposed to support variety of applications and dimensionality but lack research works has been conducted in terms of supporting scale dimension. Generally, the Dual Half Edge (DHE) data structure was designed to work with any perfect 3D spatial object such as buildings. In this paper, we attempt to expand the capability of the DHE data structure toward integration with scale dimension. The description of the concept and implementation of generating 3D-scale (2D spatial + scale dimension) for the DHE data structure forms the major discussion of this paper. We strongly believed some advantages such as local modification and topological element (navigation, query and semantic information) in scale dimension could be used for the future 3D-scale applications.
Highlights
An ideal 3D or 4D spatial model must have capability to support most of basic analysis or/and advance analysis
There is a wide category or definition on the third dimensional model; a 2D geometry that consists of spatial dimension of coordinate X and Y, and the third one is used to represent with other non-spatial dimension such as scale, time and etc (Oosterom, 2005)
Extrude by Point is the new contribution as far as the extrusion techniques for scale dimension is concerned. This technique reduces the number of edges, faces and the cost of storage for the model compared to Triangulated Irregular Network (TIN); especially to handle the case of polygon within polygon (A within B; an island is bounded by the sea or water)
Summary
An ideal 3D or 4D (a spatial 3D with additional non-spatial dimension) spatial model must have capability to support most of basic analysis or/and advance analysis. There are three basic requirements that need to be preserved in order to provide basic and complex analysis in n-dimensional (where n>1) spatial model representation. The selection of data structure for model implementation should meet all GIS data requirements in order to widen the analysis functions in the 3D/4D spatial model. The 3D/4D spatial data model supposedly able to support geometry, topology and semantic integration within a single model. As compared to other data structures available in market such as CAD system, the DHE able to provide the most consistent GIS elements such as geometry, topology and attribute within single data structure. The emergence of scale element for the nonspatial dimension has taking the lead in the GIS modelling research trend for the past few years. The remaining sections describe the new approach on scale generalization, results and conclusion
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