Problems opening NetCDF file

• To: visad-list@xxxxxxxxxxxxx
• Subject: Problems opening NetCDF file
• From: Darren Webb <darren@xxxxxxxxxxxxxxxxxx>
• Date: Mon, 03 Aug 1998 12:20:57 +0930

Hi

I'm a first time user of VisAD, evaluating its potential for
a meteorological application.  I'm having some degree of
difficulty getting started reading from a large NetCDF file.
Basically, I have this bit of code:

>     public static void main(String[] args) throws Exception
>     {
>       // create a data reference for the image
> System.err.println("creating a data reference");
>       final DataReference data_ref = new DataReferenceImpl("data");
> 
>       // open a NetCDF file with the time sequences
> System.err.println("opening the data sequence "+args[0]);
>       Plain plain = new Plain();
>       FlatField data_sequence = (FlatField) plain.open(args[0]);
>     }

And I get this result:

> sun4:darren@krypton:bom-data> java ReadGrid a19970701.nc
> creating a data reference
> opening the data sequence a19970701.nc
> Exception in thread "main" visad.SetException: Gridded2DSet: samples do not 
> form a valid grid (0,0)
>         at visad.GriddedSet.create(Compiled Code)
>         at visad.GriddedSet.create(Compiled Code)
>         at visad.GriddedSet.create(Compiled Code)
>         at visad.data.netcdf.in.NcFunction.getGriddedSet(Compiled Code)
>         at visad.data.netcdf.in.NcFunction.getDomainSet(Compiled Code)
>         at visad.data.netcdf.in.NcNestedFunction.<init>(Compiled Code)
>         at visad.data.netcdf.in.NcFunction.newNcFunction(Compiled Code)
>         at visad.data.netcdf.in.NcData.newNcData(Compiled Code)
>         at visad.data.netcdf.in.NetcdfAdapter.getDataSet(Compiled Code)
>         at visad.data.netcdf.in.NetcdfAdapter.<init>(Compiled Code)
>         at visad.data.netcdf.Plain.open(Compiled Code)
>         at ReadGrid.main(Compiled Code)

The header of the NetCDF file I'm trying to read looks like:

> netcdf a19970701 {
> dimensions:
>         lon = 360 ;
>         lat = 181 ;
>         lvl = 19 ;
>         time = UNLIMITED ; // (4 currently)
>         char_size = 4 ;
> variables:
>         float lon(lon) ;
>                 lon:long_name = "longitudes" ;
>                 lon:type = "ll      " ;
>                 lon:units = "degrees_E" ;
>         float lat(lat) ;
>                 lat:long_name = "latitudes" ;
>                 lat:type = "ll      " ;
>                 lat:units = "degrees_N" ;
>         float lvl(lvl) ;
>                 lvl:long_name = "vertical levels" ;
>                 lvl:type = "pressure" ;
>                 lvl:units = "hPa" ;
>                 lvl:positive = "down" ;
>         float time(time) ;
>                 time:units = "days since 1997-06-30 23:00:00" ;
>         char seg_type(time, char_size) ;
>                 seg_type:long_name = "segment of bmrc header type" ;
>         int tm_step_size ;
>                 tm_step_size:long_name = "time step size" ;
>                 tm_step_size:units = "seconds" ;
>         int base_date(time) ;
>                 base_date:long_name = "base date (YYYYMMDD) of this segment" ;
>         int base_time(time) ;
>                 base_time:long_name = "base time (HHMM) of this segment" ;
>         int valid_date(time) ;
>                 valid_date:long_name = "valid date (YYYYMMDD) of this 
> segment" ;
>         int valid_time(time) ;
>                 valid_time:long_name = "valid time (HHMM) of this segment" ;
>         float sfc_geop(time, lat, lon) ;
>                 sfc_geop:grid_type = "spatial" ;
>                 sfc_geop:level_type = "single" ;
>         float air_temp(time, lvl, lat, lon) ;
>                 air_temp:grid_type = "spatial" ;
>                 air_temp:level_type = "multi " ;
>         float mix_rto(time, lvl, lat, lon) ;
>                 mix_rto:grid_type = "spatial" ;
>                 mix_rto:level_type = "multi " ;
>         float zonal_wnd(time, lvl, lat, lon) ;
>                 zonal_wnd:grid_type = "spatial" ;
>                 zonal_wnd:level_type = "multi " ;
>         float merid_wnd(time, lvl, lat, lon) ;
>                 merid_wnd:grid_type = "spatial" ;
>                 merid_wnd:level_type = "multi " ;
>         float geop_ht(time, lvl, lat, lon) ;
>                 geop_ht:grid_type = "spatial" ;
>                 geop_ht:level_type = "multi " ;
>         float mslp(time, lat, lon) ;
>                 mslp:grid_type = "spatial" ;
>                 mslp:level_type = "single" ;
> 
> // global attributes:
>                 :history = "Produced by BMRC DP V15 19970711 15:48" ;
>                 :conventions = "COARDS" ;
>                 :modl_vrsn = "gam04e  " ;
>                 :arch_vrsn = "g2.0    " ;
>                 :expt_id = "T79     " ;
> }

This file can be read with NetCDF 3.4.  Don't ask me anything about the
data,
it's not mine!  It is in excess of 100Mb, and I have tried difference VM
stack sizes.
Any suggestions would be appreciated.

Thanks
Darren
-- 

Darren Webb, B.Sc(Ma. & Comp. Sci.) Hons.
Distributed High Performance Computing Group
Department of Computer Science
University of Adelaide
South Australia 5005
AUSTRALIA
Phone: +61 0412 534 842
Email: darren@xxxxxxxxxxxxxxxxxx
WWW: http://www.cs.adelaide.edu.au/~darren

  dopelar effect (n.)
  the tendency of stupid ideas to seem smarter when they
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