| Re: AVHRR Image Mapping Problem [message #51999 is a reply to message #51852] |
Sun, 24 December 2006 10:03   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Chris Torrence writes:
> Just another data point: The PDF document on the GIMMS website states that
> the images are projected onto the Clarke 1866 Ellipsoid, while the GeoTIFF
> tags in the file indicate that it is WGS-84. I wonder which one is correct.
>
> Now, switching to the Clarke 1866 ellipsoid didn't actually help (it
> probably only changes it by a few hundred meters or so), but it makes you
> wonder whether the rest of the GeoTIFF information is accurate given that
> the ellipsoid is incorrect...
A ray of light today. :-)
Using Chris's initial instructions for how to open and
read this GeoTiff file in iMap resulted in the same slight
mismatch between the continental outlines and the image.
However, this morning I went back to iMap to try again.
This time, after I read the geotiff file into iMap, I
chose Map Register Image from the Operations menu. Viola!
Now when I add continental outlines, they map perfectly.
But, WHERE is this happening in the iTool code!?
Your guess is as good as mine. I'm now convinced this
can be done in IDL. But I still want to know HOW.
Chris, can you give us any insight into how that
iRegister Map wizard works?
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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