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20040419: reading non-McIDAS files into McIDAS



>From: Joe Barrett <address@hidden>
>Organization: FSU
>Keywords: 200404191934.i3JJYZCT009529 McIDAS AREA GVAR PNG

Joe,

>I would like to know if it is possible to use the LDM decoder pnga2area to
>convert any PNG file to an AREA-file format.

No.

>Or, does the PNG file have
>to be converted from an AREA file to a PNG file in the first place?

Yes.  The images sent in the Unidata-Wisconsin datastream (IDD feed
type UNIWISC (aka MCIDAS)) are compressed before being sent as IDD
products.  The compressions does not, however, include the header
and trailer portions of the AREA file.  Those portions are included
at the beginning of the product in an uncompressed form.  The actual
image portion of the image is PNG compressed and added after the
header and trailer portions.

>At
>FSU, our Direct-Met software is reading satellite imagery in GVAR format
>and saving it to BMP files that contain additional metadata to read
>temperatures and lat/long while viewing the BMP file.  I was wondering if
>it was possible to convert the BMP file to a PNG file, then use the
>pnga2area program.

No, but it should be possible to take the BMP images and convert them
into AREA format.  To correctly do this, however, you would have to
have the navigation information that corresponds to the individual
images.  This is available in the Unidata-Wisconsin images.  So, the
process of converting your GVAR images would be to:

- create an AREA file header that includes the navigation block
  that is correct for your image

- write the image portion into the new AREA

>Just as importantly, I have not figured out how to read or convert GVAR
>files in McIDAS.

>I assume that it is necessary to first convert the raw
>GVAR file into AREA format.  I have seen a couple utilities available
>for GVAR conversion, but have not figured out how to get them to work.

Which applications are you referring to?

>Any help would be greatly appreciated.

Do you have an example GVAR image file that you want to convert
(a small one would do)?  If yes, I can ask SSEC if they have a routine
that can be used to convert the file into an AREA.

>Joe Barrett (address@hidden)
>research assistant for Dr. Paul Ruscher
>Florida State University

Cheers,

Tom Yoksas
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