| Re: closed contour paths: clockwise or anticlockwise - or actually a mixture? [message #87071 is a reply to message #87070] |
Fri, 03 January 2014 13:13  |
George.millward
Messages: 26
Registered: October 2012
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Junior Member |
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On Friday, January 3, 2014 2:01:23 PM UTC-7, David Fanning wrote:
> George.millward@yahoo.com writes:
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>> Hi there,
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>> I'm doing some very straightforward contour plotting - but instead of actually plotting the contours - I'm writing out the path data of closed contours by using the path_info and path_xy keywords.
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>> This is all working fine, but I have a problem: Some of the contour paths (written out as x,y arrays) close in a clockwise order, some close in an anticlockwise order. This is causing trouble when I export the paths to other mapping software because the latter is strictly wanting the paths to always be clockwise.....
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> This seems unlikely. Are you sure you are not confusing the high and low
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> contours? In other words, one path describes a mound, the other path
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> describes a hole. The normal should be pointing toward you in the
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> counterclockwise (mound) contour, and away from you in the clockwise
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> (hole) contour.
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> Cheers,
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> David
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> --
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> David Fanning, Ph.D.
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> Fanning Software Consulting, Inc.
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> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
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> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
David,
Aha - I think that's it. Thanks. I think a contour that is 'high' (above it's surroundings) is written in clockwise order - but if it is a 'hole' it is written is anti-clockwise order. Is that your understanding?
[For anyone trying to follow this thread the relevant parameter here is path_info.high_low]
Cheers
George.
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