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[IDD #OLV-956032]: IDD Participation

Hi Brian,

re:
> Hi Tom, I did a google search on the "gini format" and got a Unisys site that
> described the same format I am looking at in the ICD document.  Namely, a 512
> byte header followed by a data portion.  I see the data portion can be
> compressed, which would account for the different record lengths. (No mention 
> is
> made of compression technique.)  However, I am not finding anything that looks
> like the header in the product.  Is it possible the entire product is getting 
> hit
> by some compression technique before it is sent out?

Yes, exactly.  The products are Zlib-compressed in chunks for broadcast in 
NOAAPort.
Both Unidata McIDAS and GEMPAK have incorporated the code necessary to 
uncompress
the image pieces on the fly for display and analysis.

In addition, the standalone 'zlibg2gini' "decoder" in the ldm-mcidas package 
contains
the code that uncompresses the images into the format described in the ICD you 
are
referencing.  I would say that your easiest path toward using the images would
be to download the ldm-mcidas package; copy the 'zlibg2gini' decoder executable
to a directory in the PATH of the user running your LDM (e.g., ~ldm/decoders, 
NOT
~ldm/bin!!); and have the decoder write out uncompressed files.  At that point 
you
would have images that you can work with.

The ldm-mcidas package is available by anonymous FTP from the Unidata FTP 
server,
ftp.unidata.ucar.edu.  There is a binary distribution built for old Linux
systems that you might be able to use "out of the box".  Here is the access
information:

<as 'ldm'>
cd ~ldm
mkdir ldm-mcidas
cd ldm-mcidas

ftp ftp.unidata.ucar.edu
  <user> anonymous
  <pass> address@hidden

  cd pub/ldm-mcidas
  binary
  get ldm-mcidas-2004.tar.Z           <- source distribution

  -- OR --

  cd pub/binary/linux_2.6-i686
  binary
  get ldm-mcidas-2004.tar.Z           <- old binary distribution for 32-bit 
Linux

  quit

tar xvzf ldm-mcidas-2004.tar.Z

cp ldm-mcidas-2004/bin/zlibg2gini ~/decoders
cp ldm-mcidas-2004/etc/SAT* ~/etc

Here is a generic one that uncompresses the GINI images from
the NIMAGE datastream:

#########################################################################
#
# NIMAGE (NOAAPORT imagery) section using using LDM-MCIDAS 'zlibg2gini'
#        decoder
#
# NOTEs:
#        - stop and restart the LDM to activate
#
#########################################################################

# All NOAAPORT Zlib-compressed (satz) GINI images
NIMAGE  ^satz/ch[0-9]/.*/(.*)/([12][0-9])([0-9][0-9])([01][0-9])([0-3][0-9]) 
([0-2][0-9])([0-5][0-9])/(.*)/(.*km)/
        PIPE    -close
        zlibg2gini -vl logs/ldm-mcidas.log
        data/mcidas/images/sat/\8/\9/\1/\1_\2\3\4\5_\6\7

NB:

- you must take care to use tabs in appropriate places in pattern-action file
  patterns:

  - tab between NIMAGE and ^satz
  - tab before PIPE
  - tab between PIPE and -close
  - tab before zlibg2gini
  - tab before data/mcidas/...

- you should adjust the output directory to suit your needs

If you need to build 'zlibg2gini' from source and run into problems (quite
possible), please open a new inquiry by sending a new email (not a reply)
to address@hidden.

> I am seeing the WMO header,
> followed by two CRs and a LF, then after that I was expecting the 512-byte
> header, but what is there is not the header.  Is there additional stuff there
> before the actual data product starts?

The stumbling block for you at the moment is the zlib-compressed blocks that
are created for the NOAAPort broadcast.

Question:

- do you really need to write a new decoder for the GINI images?

- another way of asking the same question is how are you intending
  to use the NIMAGE GINI images?

Again, both Unidata GEMPAK and McIDAS have been configured to use
the zlib-compressed images as is (they, of course, can also use
the uncompressed images).

> Thanks... Brian

No worries.


Cheers,

Tom
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Ticket Details
===================
Ticket ID: OLV-956032
Department: Support IDD
Priority: Normal
Status: Closed