Cartographic line simplification : a formal role within digital cartographic production

This study examines the role of cartographic line simplification in traditional map production, and explores how that role can be transformed to digital map production. Whilst previous studies theoretically recognised that simplification is only a sub-process within the general context of generalisation, they, in practical terms, have inappropriately utilised digital simplification algorithms. For example, they confuse the role of simplification with that of generalisation. Consequently, there has been little, if any, progress in the field of formalising the process of cartographic line simplification, so as to be able to perform a truly digital cartographic simplification consistent with the requirements of cartographic generalisation. Recently, there have been calls to study cartographic processes before contriving new algorithms. This study is, therefore, a response of such calls, and proposes a novel scheme by which the process of line simplification is re-examined in both the traditional and digital realms. The proposed scheme consists of three consecutive logical stages. The first stage is concerned with examination of the definition of the traditional line simplification. The second stage is concerned with evaluation of a typical widely-used digital simplification algorithm, in this case, the Douglas-Poiker algorithm, according to its underlying design specifications. The third stage involves searching for cartographic quality in the output of the algorithm, assisted by post processing by a Cubic Spline smoothing routine.;Overall, a formulation of the cartographic role for the two simplification algorithms in digital cartographic generalisation is presented. The formulation can serve as a practical solution for an objective use of the two algorithms within digital mapping systems during digital cartographic productions. The study also shows that the process of simplification is a complex process, which is like any context-dependent generalisation process. Further effort will be required, however, to achieve a sound exhaustive understanding of the concept and practice of the line simplification and hence its formulation. Furthermore, the optimal goal of this work is to provide an operational model for cartographic line simplification, and a present a feasible methodology with which researchers can examine other generalisation processes.