Re: [netcdf-java] Creating NetCDF files with GeoGrids

• To: Anthony Fox <anthony@xxxxxxxx>
• Subject: Re: [netcdf-java] Creating NetCDF files with GeoGrids
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Tue, 22 Jul 2008 16:16:51 -0600

If you already have a file with georeferencing info in it which can be made 
into a geogrid, then geogrid.writeFile() (or its replacement in 4.0 
NetcdfCFWriter) can be used. If you are writing the file from scratch, then you 
need to use a metadata convention, and we recommend CF:




Anthony Fox wrote:

Hello,

I am trying to create a NetCDF file with a GeoGrid.  My data is a
200x200 grid indexed by latitude and longitude.  Each grid point has a
"prediction" value that is a double ranging from 0 to 1.  Can I create
a NetCDF file from this data?  I have tried the code following but ran
into trouble trying add a coordinate system.  Any help in creating a
NetCDF file from this data set would be appreciated.

Thanks,
Anthony


        NetcdfFileWriteable ncfile = NetcdfFileWriteable.createNew(
                "mypredfile");
        // add dimensions
        Dimension latDim = ncfile.addDimension("lat", 200);
        Dimension lonDim = ncfile.addDimension("lon", 200);
        ArrayList<Dimension> dims = new ArrayList<Dimension>();
        dims.add(latDim);
        dims.add(lonDim);

        ncfile.addVariable("prediction", DataType.DOUBLE, dims);
        Variable predvar = new Variable(ncfile, ncfile.getRootGroup(),
null, "prediction");
        predvar.setDataType(DataType.DOUBLE);
        predvar.setDimensions(dims);
        VariableDS predVariable = new
VariableDS(ncfile.getRootGroup(), predvar, true);

        // ???????????????????????
        //  predVariable.addCoordinateSystem(new
CoordinateSystem(ncfile, arg1, arg2));
        ncfile.create();

        ArrayDouble preds = new ArrayDouble.D2(latDim.getLength(), lonDim.
                getLength());
        Random rand = new Random();
        for (int i = 0; i < latDim.getLength(); i++) {
            for (int j = 0; j < lonDim.getLength(); j++) {
                preds.setDouble(preds.getIndex().set(i, j), rand.nextDouble());
            }
        }
        ncfile.write("prediction", new int[2], preds);
        ncfile.close();


       /* IS THIS CORRECT?????
        GridDataset gd = new ucar.nc2.dt.grid.GridDataset(NetcdfDataset.
                openDataset("mypred"));
        GeoGrid grid = new GeoGrid(gd, new
VariableDS(ncfile.getRootGroup(), ncfile.getVariables().
                get(0), true), new GridCoordSys(null, null));
                ncfile.create();
        grid.writeFile("mypredwithgrid");
        */
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• References:
  • [netcdf-java] Creating NetCDF files with GeoGrids
    • From: Anthony Fox