Re: [Fwd: [netcdf-java] grib2 read error]

comments below.



> -------- Original Message --------
> Subject: [netcdf-java] grib2 read error
> Date: Wed, 21 Jan 2009 23:34:54 -0500
> From: Sachin Kumar Bhate <address@hidden>
> Reply-To: address@hidden
> Organization: Mississippi State University-Northern Gulf Institute
> To: address@hidden
>
> John,
>
> I am trying to read a section of aggregated grib2 data files.
> All subsets are read fine except when start index for time range
> is '0'.
>
> I have tested this with nj2.22 as well as 4.0 (developmental version).
>
> A sample code is shown below.
>
> >>>> start
> String uri = ww3-multi.ncml;
> String var='Significant_height_of_combined_wind_waves_and_swell';
>
>             GridDataset gid = GridDataset.open(uri);
>             GeoGrid Grid = gid.findGridByName(var);
>
>             Range trange = new Range(0,3,1);          // start time
> index = 0 gives error, all other start time index have no problem
>             Range yrange = new Range(1,20,1);
>             Range xrange = new Range(1,40,2);
>
>              GeoGrid subg = Grid.subset(trange,null,yrange,xrange);
>
>             VariableEnhanced  ve= subg.getVariable();
>             Array d = ve.read();
>             gid.close();
>
> <<<<<< end
>
> I get this error..
>
> java.lang.NullPointerException
>    at
> ucar.grib.grib2.Grib2DataSection.jpeg2000Unpacking(Grib2DataSection.java:797)
>    at ucar.grib.grib2.Grib2DataSection.<init>(Grib2DataSection.java:131)
>    at ucar.grib.grib2.Grib2Data.getData(Grib2Data.java:129)


Sachin,

This was an unusal report, the problem is a corrupt file, not NcML

file multi_1.at_4m.hs.200502.grb2 has a bad data section in the 
following record from the index. I believe it's
Significant Height of swell waves.


0 10 0 8 2 241 1.0 255 0.0 2005-02-01T00:00:00Z 3 1391515031 21097354 
21097426

Since the corruption is at valid time 3, that why later offset probably 
worked ok.

In the future if you see this problem again, use ToolsUI to display the 
data. I going to make the jpeg decoder catch these errors, return a 
error message and set the data values to the missing values.

Robb...

>    at
> ucar.nc2.iosp.grib.Grib2ServiceProvider._readData(Grib2ServiceProvider.java:86)
>    at
> ucar.nc2.iosp.grib.GribServiceProvider.readXY(GribServiceProvider.java:291)
>    at
> ucar.nc2.iosp.grib.GribServiceProvider.readData(GribServiceProvider.java:253)
>    at ucar.nc2.NetcdfFile.readData(NetcdfFile.java:1368)
>    at ucar.nc2.Variable._read(Variable.java:926)
>    at ucar.nc2.Variable.read(Variable.java:621)
>    at ucar.nc2.ncml.Aggregation$Dataset.read(Aggregation.java:1250)
>    at ucar.nc2.ncml.Aggregation.read(Aggregation.java:689)
>    at ucar.nc2.dataset.VariableDS._read(VariableDS.java:277)
>    at ucar.nc2.Variable.read(Variable.java:646)
>    at SubsetGrid.main(SubsetGrid.java:55)
>
>
> For test purposes the NcML and grib files (zipped) can be accessed via
>
> http://www.gri.msstate.edu/rsearch_data/nopp/ww3-multi.zip
>
> thanks,
>
> -Sachin
>
> --
> Sachin Kumar Bhate, Research Associate
> MSU-High Performance Computing Collaboratory, NGI
> John C. Stennis Space Center, MS 39529
> http://www.northerngulfinstitute.org/
>
>
>
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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/
===============================================================================