| Re: AVHRR Image Mapping Problem [message #51990 is a reply to message #51852] |
Fri, 15 December 2006 10:50   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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kuyper@wizard.net writes:
> Actually, yes. I have no idea why the standard parrallels might be
> incorrect, but given the symptoms you describe, it might be worthwile
> to try 19.99999 and -20.00001. IDL doesn't like it when the standard
> parallels add up to exactly zero. That is unfortunate, because a Albers
> projection with standard parallels adding up to zero is a different way
> of describing the cylindrical equal-area projection, one of my favorite
> map projections, and one that IDL doesn't support.
Here are the results. Possibly a bit better.
Here are the results with parallels at "normal"
-19 and 21.
http://www.dfanning/misc/normal.png
Here are the results with parallels at -19.9999 and 20.0001.
http://www.dfanning/misc/kuyper.png
The results using parallels of 19.9999 and -20.001 are
identical to that above. As are the results if I switch
the values for STANDARD_PAR1 and STANDARD_PAR2.
If you load these in your browser and hit your back
and forward buttons, you can see a little movie of
these projections switching back and forth. Don't know
what that shows, but it distracts me from the real
problem. :-)
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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