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20060106: Converting MCIDAS images to GEMPAK format for Garp



>From: Nancy Selover <address@hidden>
>Organization: ASU
>Keywords: 200601061910.k06JAO7s023394 ldm-mcidas pnga2area

Hi Nancy,

>I have downloaded some GOES-10 images in the uncompressed MCIDAS format
>(filenames YYMMDD_band.are  where band = IR, WV or VIS).

Where did you download these images from (i.e., how do you know what
format they are actually in)?

>They are in an
>archive directory structure that mirrors the real-time data directories,
>and I have created an archive version of Gemenviron that points to the
>archive structure.  The models, surface and upper air data all work fine
>with Garp, but when I try to view the images in Garp, I get an immediate
>crash when I get to the IR directory, with the error message:  *** glibc
>detected *** free(): invalid next size (fast): 0x0flbbc98 ***

Chiz will address this issue after we figure out if there are any
problems with the images you downloaded.

>I have a
>bunch of the ...ir.are  files in that directory, but I did convert one
>with pnga2area using the statement:
>
>/huser/ldm/decoders/pnga2area -a /huser/ldm/etc/SATANNOT -b
>/huser/ldm/etc/SATBAND -f 050726_ir.are
>/huser/arcdata/gempak/data/gempak/images/sat/GOES-10/4km/IR/IR_%Y%m%d_%H
>%M     (all on one line)
>
>The converted file shows up with a size of 2816, rather than 2439296
>like the uncompressed MCIDAS, so I suspect the decoding is not working.

Your opening comment was tha the images you dowloaded were in the
'uncompressed' McIDAS format (presumably AREA).  If this is true, 
there is no need to run pnga2area on them, and running it would
produce something that is totally unusable.

Question:  what is the size of your original images like 050726_ir.are?

>Is the crashing problem in the decoding, or is it just that I have the
>*.are files in that directory?  It crashed the same way before I decoded
>any files.

Let's first determine whether or not your images are OK.  If they
are, then Chiz can address the Garp-related issue(s).  If you don't
run McIDAS, the easiest way to determine if the images are OK is
to send us two or three.  I can then look at them using McIDAS and
tell you if they are viable.  If they are, then there is likely something
wrong with your setup to see the files in Garp, or in Garp itself.

>Thanks for the help.  I normally decode MCIDAS in real-time and store
>files in the GEMPAK format, so this is new to me.

Just so you know, the GOES imagery in the IDD UNIWISC (aka MCIDAS)
feed are PNG compressed McIDAS AREA files.  Running pnga2area on
them simply uncompresses them.  GEMPAK directly supports the McIDAS
AREA format (which is uncompressed) and the PNG compressed format
the IDD images are broadcast in.

Cheers,

Tom Yoksas
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