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Re: decoders] First post - GRIB2 decoders

On Wed, 20 Feb 2008, Jelle Ferwerda wrote:



Hi all,

A few moments I subscribed to the decoders mailing list. Great facility.

I am looking for some assistence.. Let me start off by explaining I am a fair 
newby when it comes to programming java, although I do have experience in IDL, 
PHP programming.

I am trying to implement a decoder to decode EUMETSET multi sensor 
precipitation estimate data 
(http://www.eumetsat.int/home/Main/Access_to_Data/Meteosat_Meteorological_Products/Product_List/SP_1119538666663?l=en
 on this page also a link to datafile downloads)

I have downloaded the GRIBjava decoder. I am now trying to build a decoder so 
that I can retrieve the MPE data.

Unfortunately when I get to the point of accessing the file and trying to get 
the individual grid definitions I get an error.

The error:


Jelle,
The Grib2 decoder isn't a batch file decoder for getting data. The idea is to make an index for the file using Grib2Indexer <fileName> and to use the Index to find what parameter to actually decode the requested parameter 
 data. The design was the result of very large Grib files.

% Grib2Dump <fileName>  shows the metadata of each record.
% Grib2Indexer <fileName>  gives the index of the file
The file IndexFormat.txt in the root of the distribution explains the details of a Grib index. sample line: 

0 0 0 6 2 103 2.0 255 0.0 2008-02-11T14:00:00Z 0 -418705429 121261 121342
% Grib2GetData <fileName> <GDS offset> <PDS offset> gets the data for record 

from above sample index line:

% Grib2GetData <fileName> 121261 121342

Don't forget to set the CLASSPATH variable to the jar file.
I'll download a test file to see if there are any problems decoding this type of data. 

Robb...




Exception in thread "main" java.lang.NegativeArraySizeException
      at 
ucar.grib.grib2.Grib2GridDefinitionSection.<init>(Grib2GridDefinitionSection.java:300)
      at exportgrb.Main.main(Main.java:71)


// Some code

   // Paths and stuff
   String InFile          = "c:\\java\\data\\MPE_20080217_0900_M9_00.grb";
   Boolean CheckTheSum = true;

  // Create a unidata specified RandomAccesFile for reading
  ucar.unidata.io.RandomAccessFile InRA = new ucar.unidata.io.RandomAccessFile(InFile, 
"r");

  // Grid definition section
  Grib2GridDefinitionSection GDSd = new Grib2GridDefinitionSection(InRA, 
CheckTheSum);
    String GGdef = GDSd.getGridName(0);
    System.out.println(GGdef);

// -- end some code

I hope that someone can help me and explain how to fix this. Or even better: Is 
there someone who has already created a decoder specifically for the 
multisensor precipitation estimates?

Thanks so much,

Kind Regards,

Jelle Ferwerda

-----------------------------------------------
Jelle Ferwerda
Postdoctoral Research Fellow

Animal Behavior Research Group
Department of Zoology / University of Oxford
South Parks Road / Oxford / OX13PS
United Kingdom

email:          address@hidden
Office Phone:   +44 18652 71214
WWW:            http://www.bio-vision.nl
-----------------------------------------------


--

-----------------------------------------------
Jelle Ferwerda
Postdoctoral Research Fellow

Animal Behavior Research Group
Department of Zoology / University of Oxford
South Parks Road / Oxford / OX13PS
United Kingdom

email:          address@hidden
Office Phone:   +44 18652 71214
WWW:            http://www.bio-vision.nl
-----------------------------------------------
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===============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
address@hidden             WWW: http://www.unidata.ucar.edu/
===============================================================================