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An Information-Based Approach for Douglas-Peucker Thresholding in Polyline Generalization

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Author Affiliations

  • 1Department of Geomatics, Faculty of Engineering, University of Tehran, Tehran, IRAN

Res. J. Recent Sci., Volume 3, Issue (11), Pages 39-45, November,2 (2014)

Abstract

Douglas-Peucker is the most widely used approach for line simplification. Stopping threshold in the standard method is defined in terms of a spatial distance specified by the user. However, the user, in many cases, is not able to set the threshold as s/he really wishes. Thus, the process is either performed again or is accepted while the ideal result is not provided yet. The aforementioned problems are probable, since the relationship between the spatial threshold, the number of saved vertices and the final formation of the line is unknown. To contribute in solving this problem, the terms "data" and "information" are defined in a line simplification context and line vertices are prioritized according to their relative influence on the whole line information. The result of data-information analysis is a diagram in which data and information are the two axes. The diagram reveals how the amount of information is changing as line vertices are decreasing gradually. It is shown that at a certain point in the diagram, the slope of information reduction increases tremendously like a waterfall. It reveals that at this point, for every omitted vertex, a large amount of information is lost and it's not worth discarding any other vertices. The user can either choose the point where s/he prefers not to lose any more information or the optimal point can be automatically recognized by the application. The results as shown in the paper diagrammatically prove that using such a method can heavily simplify map simplification process.

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