Ž . ISPRS Journal of Photogrammetry & Remote Sensing 55 2000 137–138
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Editorial
Theme Issue on Dynamic and Multi-Dimensional GIS
This is a collection of papers originally presented at two international conferences. One of them was the International Workshop on Dynamic and Multi-Dimensional GIS, which was organised in August 1997 in Hong Kong by Y.C. Lee and Zhi-Lin Li of the Hong Kong Polytechnic University. The other one was the Symposium of ISPRS Commission IV, which was organised in September 1998 in Stuttgart by Dieter Fritsch of Stuttgart University. The ISPRS Working Group IVrIII.1 AGIS Fundamentals and Spatial DatabasesB was responsible for several ses-sions in both meetings. The articles published in this issue of the ISPRS Journal are a selection of the papers presented in those sessions. Although these papers have been previously published in the respec-tive proceedings, they appear here in this theme issue much revised and expanded.
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Geographic Information Systems GIS have evolved from simple two-dimensional map drafting systems in the early 1960s to fairly sophisticated information systems for spatial data of the present day. Two keywords often used to describe current
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GIS or more accurately a vision of the AultimateB .
GIS are dynamic and multi-dimensional. By dy-namic, we imply the ability of the system to capture the ever-changing world, and by multi-dimensional, we mean the liberation of spatial data from the confines of the two-dimensional space of traditional maps. When we go beyond the third dimension, we often think of time, an important attribute of a dynamic system. However, a multi-dimensional GIS does not necessarily contain time as one of its co-ordinates. In fact, a multi-attribute database in the traditional sense is multi-dimensional, if we consider each attribute as a co-ordinate in some kind of space.
Two papers in this issue have addressed the space issue and the tessellation of space into manageable units of interest to GIS applications. Lee proposes a taxonomy of space tessellation and examines the process of abstracting real-world objects into differ-ent kinds of space when creating a spatial database. Gold, on the other hand, looks at space from a topological perspective and argues that a tessellation of the world and its features into Voronoi polygons
Žor its dual of Delaunay triangles could create a.
global topological space.
Real-world objects and phenomena are not only dynamic but also fuzzy in definition. Molenaar and Cheng address the dynamics of fuzzy objects. They developed formalism for their description and a method to identify these objects and their evolution in time. GIS databases evolve not only because the world is changing, but also as a result of operations performed on them over time. Gahegan and Ehlers examine how the quality of spatial data evolves when it is transformed from raw image data col-lected by remote sensing satellites to geo-referenced and interpreted data stored in spatial databases. They suggest that such a transformation would go through
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three operations image capture, image classification,
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and object formation and document the error sources and their effects on these operations.
Modelling how features change is one thing, but detecting if they have changed is sometimes a more difficult and expensive task in practice. Winter
ex-Ž .
amines the location similarity or dissimilarity of discrete spatial objects that could represent an object that has evolved with time or two objects from different sources not of the same quality. He pro-poses seven measures that are symmetric,
nor-0924-2716r00r$ - see front matterq2000 Elsevier Science B.V. All rights reserved. Ž .
Editorial 138
malised, and dimensionless. One class of these mea-sures indicates how much two discrete regions over-lap, while the other group indicates how much they do not. He concludes that an effective similarity indicator needs measures from both classes. Ragia and Winter, on the other hand, focus on the quality evaluation of building using topological and geomet-ric measures. For the topological comparison, region adjacency graphs are used. Their approach for geo-metric comparison is to superimpose two layers of buildings covering the same region and to concen-trate their analysis on the areas where the corre-sponding buildings do not overlap.
Issues related to the dynamic and multi-dimen-sional nature of modern GIS are vast and deep. We can only cover a small tip of the iceberg in this theme issue and hope that it will spark interest in the ISPRS community on such challenging topics. We
are grateful for the invitation from the Editor-in-Chief, Manos Baltsavias, to produce this issue and for the effort of the authors and the reviewers to make this issue possible.
Y.C. Lee
Department of Geodesy and Geomatics Engineering, UniÕersity of New Brunswick,
P.O. Box 4400 Fredericton, NB, Canada E3B 5A3 E-mail address: yclee@unb.ca
Martien Molenaar
ITC, DiÕision of Geoinformatics and
