Re: [netcdf-java] Rotated-pole data

The problem is that the rotated lat/lon requires longitudes in the range 
+/- 180, see

http://www.unidata.ucar.edu/software/netcdf-java/reference/StandardCoordinateTransforms.html#rotated_pole

however, theres a bug (at least in 4.2) thats not handling scale/offset 
corectly for CoordinateAxis1D, in case you wanted to try to correct in 
NcML. I am working on a fix for that.

If you can change longitude values directly in the file it should work.

On 5/20/2010 12:23 PM, Jon Blower wrote:
> Aha!  I'd done the hard stuff and forgotten the most obvious thing.
> Adding the global Conventions attribute seems to get the coordinate
> transformation working.  However, I can't seem to read data properly: I
> just get missing values.  I know that the data are valid because if I
> don't set the Conventions attribute, I can read data fine (but they end
> up in the wrong place).  I don't understand why this might be.
>
> I've attached the data file and its NcML wrapper.
>
> Cheers, Jon
>
> -----Original Message-----
> From: John Caron [mailto:address@hidden]
> Sent: 20 May 2010 17:48
> To: Jon Blower
> Cc: address@hidden
> Subject: Re: [netcdf-java] Rotated-pole data
>
> try adding global attribute
>
>    :Conventions = "CF-1.0"
>
>
> if that doesnt work, send me the actual file.
>
> On 5/20/2010 10:39 AM, Jon Blower wrote:
>    
> > Hi,
> >
> > I have some data in rotated-pole coordinates and I'm struggling to get
> > NetCDF-Java (latest 4.1 version) to recognise the coordinate system.
> >      
> I
>    
> > think I'm following CF except that I'm not providing values for the
> >      
> true
>    
> > lon and lat values at each grid point.  I was assuming that if I
> > provided the grid mapping details that NetCDF-Java might recognise
> >      
> them
>    
> > and be able to transform to and from true lat-lon without them (i.e.
> > this information is redundant).
> >
> > However, when I load up the file in ToolUI (4.1) the projection (as
> > revealed under the tabs FeatureTypes->Grids) remains LatLon.
> >
> > The CDL is at the end of the email.  What am I doing wrong?  Or is it
> >      
> in
>    
> > fact compulsory to provide the true lon and lats at each grid point?
> >
> > Thanks,
> > Jon
> >
> > netcdf
> >
> >      
> file:C:/Godiva2_data/Rotated-pole/Stefano/04203_qwq111.oper00.pp_001.MOP
>    
> > Su.ncml {
> >    dimensions:
> >      Longitude = 360;
> >      Latitude = 288;
> >      Surface = 1;
> >      Time = UNLIMITED;   // (4 currently)
> >    variables:
> >      float Longitude(Longitude=360);
> >        :units = "degrees";
> >        :long_name = "longitude in rotated-pole grid";
> >        :standard_name = "grid_longitude";
> >      float Latitude(Latitude=288);
> >        :units = "degrees";
> >        :long_name = "latitude in rotated-pole grid";
> >        :standard_name = "grid_latitude";
> >      float Surface(Surface=1);
> >        :units = "surface";
> >        :positive = "down";
> >      float Time(Time=4);
> >        :units = "days since 2007-07-26 11:00:00";
> >        :long_name = "time";
> >      float Dynamic_rainfall_rate(Time=4, Surface=1, Latitude=288,
> > Longitude=360);
> >        :units = "kg m-2 s-1";
> >        :long_name = "LARGE SCALE RAINFALL RATE KG M-2 S-1";
> >        :title = "LARGE SCALE RAINFALL RATE KG M-2 S-1";
> >        :source = "UM output";
> >        :missing_value = -32768.0f; // float
> >        :_FillValue = -32768.0f; // float
> >        :grid_mapping = "rotated_pole";
> >      char rotated_pole;
> >        :grid_mapping_name = "rotated_latitude_longitude";
> >        :grid_north_pole_latitude = "37.5";
> >        :grid_north_pole_longitude = "177.5";
> >
> >    :History = "Created_by_convert_pp_2_netcdf_at_NCEO";
> > }
> >
> > --
> > Dr Jon Blower
> > Technical Director, Reading e-Science Centre
> > Environmental Systems Science Centre
> > University of Reading
> > Harry Pitt Building, 3 Earley Gate
> > Reading RG6 6AL. UK
> > Tel: +44 (0)118 378 5213
> > Fax: +44 (0)118 378 6413
> > address@hidden
> > http://www.nerc-essc.ac.uk/People/Staff/Blower_J.htm
> >
> >
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