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Re: contour over a map and 180 degrees off or problems with dateline [message #53823 is a reply to message #53740]

Wed, 02 May 2007 12:32

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

teich@atmsci.msrc.sunysb.edu writes:

> If I keep the lon array as is (i.e., -177.5, ..., +177.5) and use your
> field=Shift(field,36,0) then everything looks in the right location
> and there is no problem at the dateline. Although this fixed the
> problem, what if I had an odd number of elements for array lon? Since
> I compare plots visually, it may be important to get the exact
> locations. Would you suggest this type of fix (using Shift) for every
> contour of this type?

Well, I don't know. These kinds of things always confuse me. :-)

It seems to me one of two things has to be wrong. (1) Your
longitude vector does really describe the physical locations
of your data (I.e., the left edge of your array is not
at -177.5 degrees of longitude), or (2) the map projection
is not centered with respect to the data (I.e., the center of
the data and the center of the map are at two different places).

I think if you resolve this problem, then shifting, which I would
only use as a last resort, would probably go away.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		contour over a map and 180 degrees off or problems with dateline By: teich on Wed, 02 May 2007 10:51
		Re: contour over a map and 180 degrees off or problems with dateline By: David Fanning on Wed, 02 May 2007 12:51
		Re: contour over a map and 180 degrees off or problems with dateline By: teich on Wed, 02 May 2007 12:48
		Re: contour over a map and 180 degrees off or problems with dateline By: David Fanning on Wed, 02 May 2007 12:32
		Re: contour over a map and 180 degrees off or problems with dateline By: teich on Wed, 02 May 2007 12:20
		Re: contour over a map and 180 degrees off or problems with dateline By: David Fanning on Wed, 02 May 2007 11:52
		Re: contour over a map and 180 degrees off or problems with dateline By: teich on Wed, 02 May 2007 11:41
		Re: contour over a map and 180 degrees off or problems with dateline By: David Fanning on Wed, 02 May 2007 11:07

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