Re: IOSP file request

Hi Peter:

attached is the example i wrote in class

Peter Miu wrote:
> Hi John,
>
> Got the message from Tom.
>
> Can you send me the IOSP file please ?
>
> I take this opportunity to ask this :
>
> Is there a minimum set of netcdf variables/attributes
> to populate for Geo-stationary satellite data sets in order
> for THREDDS and IDV to work.  I know this may be difficult
> to answer as you don't know the source data set but I'm
> looking for things like :
>
> Need to populate CF identifiers:

"standard names" are not needed

> lon, lat, temperature, ...

the minimum set is the information for geolocation. typically the lat, lon
variables or the x, y and the projection info.

if its got a time dimension, you need the time coordinate.
if its got a vertical dimension, you need the vertical coordinate.

this may be helpful:

 
http://www.unidata.ucar.edu/software/netcdf-java/tutorial/CoordinateAttributes.html

If you need to be "CF-compliant" the details are somewhat different, but the
same ideas are used.

When you have a specific dataset, i can help you with more details.

John

package ucar.nc2.iosp.misc;

import ucar.nc2.*;
import ucar.nc2.dataset.NetcdfDataset;
import ucar.nc2.util.CancelTask;
import ucar.unidata.io.RandomAccessFile;
import ucar.ma2.Array;
import ucar.ma2.InvalidRangeException;
import ucar.ma2.DataType;
import ucar.ma2.Range;

import java.io.IOException;
import java.util.List;


public class GtopoIosp {

    public boolean isValidFile(RandomAccessFile raf) throws IOException {
        return raf.getLocation().endsWith(".DEM");
    }

    private RandomAccessFile raf;

    public void open(RandomAccessFile raf, NetcdfFile ncfile, CancelTask
    cancelTask) throws IOException {
      this.raf = raf;

        Dimension latd = new Dimension("lat", 6000, true);
        Dimension lond = new Dimension("lon", 4800, true);
        ncfile.addDimension(ncfile.getRootGroup(), latd);
        ncfile.addDimension(null, lond);

        ncfile.addAttribute( null, new Attribute("Conventions", "CF-1.0"));


        Variable elev = new Variable(ncfile, null, null, "elevation");
        elev.setDataType( DataType.SHORT);
        elev.setDimensions( "lat lon");
        ncfile.addVariable(null, elev);

        elev.addAttribute( new Attribute("missing_value", (short) -9999));
        elev.addAttribute( new Attribute("units", "m"));
        elev.addAttribute( new Attribute("units_desc", "meters above sea
        level"));
        elev.addAttribute( new Attribute("long_name", "elevation four GTOPO
        modell"));

        Variable lat = new Variable(ncfile, null, null, "lat");
        lat.setDataType( DataType.FLOAT);
        lat.setDimensions( "lat");
        ncfile.addVariable(null, lat);
        lat.addAttribute( new Attribute("units", "degrees_north"));

        Variable lon = new Variable(ncfile, null, null, "lon");
        lon.setDataType( DataType.FLOAT);
        lon.setDimensions( "lon");
        ncfile.addVariable(null, lon);
        lon.addAttribute( new Attribute("units", "degrees_east"));

        Array lonData = NetcdfDataset.makeArray(DataType.FLOAT, 4800,
        -139.99583333333334, 0.00833333333333);
        lon.setCachedData(lonData, true);

        Array latData = NetcdfDataset.makeArray(DataType.FLOAT, 6000,
        89.99583333333334, -0.00833333333333);
        lat.setCachedData(latData, true);
    }

    public Array readData(Variable v2, List section) throws IOException,
    InvalidRangeException {
      int size = (int) Range.computeSize( section);
      short[] data = new short[size];

      raf.seek(0);
      raf.order(RandomAccessFile.BIG_ENDIAN);

      RegularIndexer index = new RegularIndexer(v2.getShape(),
      v2.getElementSize(), 0, section, -1);
      while (index.hasNext()) {
        Indexer.Chunk chunk = index.next();
        raf.seek ( chunk.getFilePos());
        raf.readShort( data, chunk.getIndexPos(), chunk.getNelems()); // copy
        into primitive array
      }

      return Array.factory(v2.getDataType().getPrimitiveClassType(),
      Range.getShape( section), data);

    }

     public void close() throws IOException {
       raf.close();
    }



    public Array readNestedData(Variable v2, List section) throws IOException,
    InvalidRangeException {
         return null;  //To change body of implemented methods use File |
         Settings | File Templates.
     }

    public boolean syncExtend() throws IOException {
        return false;  //To change body of implemented methods use File |
        Settings | File Templates.
    }

    public boolean sync() throws IOException {
        return false;  //To change body of implemented methods use File |
        Settings | File Templates.
    }

    public void setSpecial(Object special) {
        //To change body of implemented methods use File | Settings | File
        Templates.
    }

    public String toStringDebug(Object o) {
        return null;  //To change body of implemented methods use File |
        Settings | File Templates.
    }

    public String getDetailInfo() {
        return null;  //To change body of implemented methods use File |
        Settings | File Templates.
    }
}