The Revival of a Victorian Art: Waterlining with a Computer

Author: Christensen Albert H. J.  

Publisher: Maney Publishing

ISSN: 1743-2774

Source: The Cartographic Journal, Vol.36, Iss.1, 1999-06, pp. : 31-41

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Abstract

This paper introduces two automated procedures that work in vector made throughout. The first procedure traces waterlines, the decorative device with which copper engravers differentiated water areas in maps before the introduction of screen-printing. The second procedure resorts to waterlines to perform the Medial-Axis Transformation (MAT), a centrelining operation originally proposed by Pattern Recognition workers. Both procedures are described at a rather high level. Noted as important is the passing on of pointers from the input shapes to the Medial-Axis via the waterlines. Those pointers are characterized as fundamental to the straightforward definition of the Medial-Axis from waterlines. The analogy between a well-known raster method and the vector waterlining and MAT are discussed and their relative merits compared. In this context, the thesis is advanced that that analogy is the reason for the universal applicability of the proposed vector method. Cartographic and Geographic Information Systems (GIS) application, such as the delimitation of sea boundaries and the centrelining of streams and streets, are illustrated and outlined in brief manner. Even briefer are the references to, as yet undeveloped, applications in those same fields. To conclude, some thoughts are ventured on the use of MAT in related disciplines, such as Pattern Recognition, Geology, and Mining.