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
> -----------------------------------------------
> _______________________________________________
> decoders mailing list
> address@hidden
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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/
===============================================================================