From Line Geometry To Area Topology
by  © P. Wade, M. Visvalingam and G.H. Kirby (1986)
CISRG Discussion Paper Series No 1, University of Hull, 48 pp
 

For the sake of posterity, please cite from the published version:
Kirby, G H, Visvalingam, M and Wade, P (1989) "The recognition and Representation of Polygons with Holes" Computer J, 32 (6), 554 - 562.

CONTENTS

1. Introduction

2. Background

3. Disassociative Area Model (DAM)
   3.1 Geometry
   3.2 Geography
   3.3 Comparison of DAM with predecessors

4. Deriving the Topology
   4.1 Extracting the Boundaries
   4.2 Forming the Containment Hierarchy

5. An application of DAM
   5.1 Background to the OS 1:625,000 Data
   5.2 Extraction of the Geometric Topology
   5.3 Identification of Area Objects
   5 .4 Summary of the Project

6. Conclusion

REFERENCES
FIGURES It is best to open the figures in another browser window, so that you can read the text while studying the figures

 ABSTRACT

Area objects are represented on a computer by geometric or locational information (which describe the course of their boundaries), topological information (which describe the areal units to which boundaries belong), and geographic or other information (which describe the objects which map onto these areal units).

Most available systems for spatial data processing require from the outset object related information, in the form of left/right or on line references or area seeds, for extracting the area topology.

This paper introduces the Disassociative Area Model (DAM) and contrasts it with other existing descriptions of areal entities. The primitive region forms the basic spatial unit for object modelling and acts as the link between the geometric and geographic components. The derivation of spatial topology focuses on the boundary, which describes one extent of a primitive region. Geographic information may be input in a variety of ways and at any convenient stage using pragmatic models derived from DAM.

ACKNOWLEDGEMENTS 

We are grateful to a number of organisations and individuals. The Science and Engineering Research Council granted the CASE studentship held by P. Wade, with the Market Analysis Division of CACI as the collaborating body. The Ordnance Survey provided a small grant and access to their data and internal documentation. The University of Hull provided the research base. 

We are also grateful to John Griffiths of the C.I.S.R.G. and David Jordan of the Department of Pure Mathematics, University of Hull, for discussions on containment tests and terminology in area topology respectively.

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