Re: [netcdf-java] Problems reading data in polar stereographic projection

• To: Jon Blower <jdb@xxxxxxxxxxxxxxxxxxxx>
• Subject: Re: [netcdf-java] Problems reading data in polar stereographic projection
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Mon, 21 Jan 2008 17:25:53 -0700

Hi Jon:

1) y coordinate is missing units attribute
2) latitude unit should be "degrees_north", not "degrees"
3) longitude unit should be "degrees_east", not "degrees"
4) most of the the data variables have "_CoordinateAxes" attributes missing the 
time coordinate, eg:

     :_CoordinateAxes = "longitude latitude y x ";

should be:

     :_CoordinateAxes = "longitude latitude y x time ";

The rule for "_CoordinateAxes" is that they have to be complete, if you are 
going to use them. If
you left "_CoordinateAxes" off, then the CF-1.0 convention

     :coordinates = "longitude latitude";

would work, since the coordinate variables (x,y,time) would be automatically 
added.

Jon Blower wrote:
> Hi all,
> 
> I'm trying to use the Java NetCDF libraries (2.2.22) to read Arctic
> ocean data over OPeNDAP.  The data are in polar stereographic
> projection.  However, the following short program (which works fine
> for many other datasets) returns zero Grids:
> 
>     NetcdfDataset nc = NetcdfDataset.openDataset(url, true, null);
>     GridDataset gd =
> (GridDataset)TypedDatasetFactory.open(DataType.GRID, nc, null, null);
>     System.out.println(gd.getGrids().size()); // prints out "0"
> 
> The URL to the OPeNDAP site is
> http://topaz.nersc.no/thredds/dodsC/topaz/mersea-ipv2/arctic/tmipv2a-class1-be.
>  The results of performing an ncdump on this URL (using toolsUI) are
> attached.  toolsUI also fails to recognize any Grids in this dataset.
> 
> Can anyone advise on what might be the problem here?  Is the metadata
> of the dataset incorrectly specified?
> 
> Thanks in advance,
> Jon
> 
> 
> 
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