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CONTOURING AND THE CONTOUR MAP: A NEW PERSPECTIVE *
Author(s) -
WREN A. E.
Publication year - 1975
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1975.tb00676.x
Subject(s) - contouring , computer science , filter (signal processing) , contour line , artificial intelligence , computer vision , algorithm , computer graphics (images) , physics , meteorology
A bstract With few exceptions, traditional approaches to contouring have been too subjective. Contouring and contour maps are too often discussed in terms more appropriate to art than to science. With hand contouring there is some justification for this attitude; with machine (i.e. programmed) contouring there is none. Hand contouring is highly susceptible to interpretive judgement and the interpreter is not bound by rigid mathematical constraints. Hence, in allowing for the interpreter's “freedom of expression” it may be difficult to evaluate hand contouring in a totally analytical and objective manner. Machine contouring, however, is based upon mathematical formulation. It is therefore a consistent and objective procedure, ideally suited to objective definition and analysis. It can be demonstrated that the combined process of sampling plus contouring constitutes a two‐dimensional filter. The contouring component is that part which introduces “distortion” or wavenumber discrimination. An ideal contour package is one that acts as an all‐pass filter where the distortion is zero. The application of filter theory to the evaluation of a machine contour package and its performance permits description in the more convenient language and terminology of the wavenumber domain, rather than that of the space domain. A more important advantage is that the contour package can be subjected to the various standards of filter evaluation such as amplitude and phase response. The practical application, as well as the benefit, of this approach is revealed through the comparison, in both the space and wavenumber domains, of contour maps generated from various machine contour packages.