| Re: how to composite a mapcoord object using geographic coordinate(no projection) [message #87706 is a reply to message #87703] |
Mon, 24 February 2014 05:58   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Yngvar Larsen writes:
> I just sent you an email with a download link for one of the SRTM tiles.
Yes, so this file doesn't pretend to have map projection information in
it. Here is the GeoTiff structure from the file:
IDL> help, geo
** Structure <7b9e5160>, 2 tags, length=72, data length=72, refs=1:
MODELPIXELSCALETAG
DOUBLE Array[3]
MODELTIEPOINTTAG
DOUBLE Array[6, 1]
I just think it is unreasonable to expect general purpose GeoTiff
readers to handle files like this. Obviously, you can fill your reader
code with multiple exceptions, etc. But, when you get a file like this,
the file itself doesn't tell you want you need to know to work with the
data properly.
I'm not saying it is *hard* to use these files. It is easy enough. I'm
just saying, you need information from outside the file, or in Jie
Zhou's case, you need to parse internal information in a non-standard
way, in order to make sense of the data. If I worked with these files
for a living, I'd take 15 minutes and write myself a reader.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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