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   -> Volume 7, Issue 7

Question: Definition of edges
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Fabio Boschetti (

PostPosted: Thu Jul 16, 1998 10:35 am    
Subject: Question: Definition of edges
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#12 Question: Definition of edges

We have developed a multiscale edge detection algorithm that is
applied to the analysis of geophysical images. Details can be found at
the web page at the bottom of the message.

The edge detector works very well, enabling the user to discrimate
features even in areas of the image that look completely flat. However
recently we encoutered some problems, where reasonably visible
features did not generated any edge. Always these feature appear close
to major features in the image.

The reason for this to happen is that the definition of 'edge', as I
found it often in the literature, is 'a local maxima of the horizontal
derivative in the direction of the local gradient'. Close to main
features in an image, some features may lie parallel to the local
gradient and as such they do not generate edges even if quite clearly
visible. This, of course, can be overcome by searching for edges
independently from the direction of the local gradient, but in this
case many spurious edges appear.

I was wondering if any of you have encountered this problem on real
world images. Also, I would like to have pointers to references where
the definition of edges is discussed, especially with regard to
multiscale analysis and image reconstruction from the edges

Thank you very much in advance.


Dr. Fabio Boschetti

Research Scientist
CSIRO - Division of Exploration and Mining
39 Fairway, Nedlands 6009
PO Box 437, Nedlands 6009
Western Australia

email -
Web page -

Tel (w) ++61 8 9284 8421
(h) ++61 8 9284 3282
Fax (w) ++61 8 9389 1906
All times are GMT + 1 Hour
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