Re: [idvusers] gridded but rotated netCDF data

Hi Brian --

The key to this is to have your file conform to CF conventions.  There
is a definition there that does have 2D lat/lon variables, since this
is very common.

>From Section 5.2 of the CF conventions document at
<http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.0/cf-conventions.html>
is this, which is what it sounds like you are describing.

dimensions:
  xc = 128 ;
  yc = 64 ;
  lev = 18 ;
variables:
  float T(lev,yc,xc) ;
    T:long_name = "temperature" ;
    T:units = "K" ;
    T:coordinates = "lon lat" ;
  float xc(xc) ;
    xc:long_name = "x-coordinate in Cartesian system" ;
    xc:units = "m" ;
  float yc(yc) ;
    yc:long_name = "y-coordinate in Cartesian system" ;
    yc:units = "m" ;
  float lev(lev) ;
    lev:long_name = "pressure level" ;
    lev:units = "hPa" ;
  float lon(yc,xc) ;
    lon:long_name = "longitude" ;
    lon:units = "degrees_east" ;
  float lat(yc,xc) ;
    lat:long_name = "latitude" ;
    lat:units = "degrees_north" ;

The thing most people leave out is the "float xc(xc)" and "float
yc(yc)" which is how these variables are identified as "coordinate
varialbles".

Anyway,  if your file is not like this but is "close", then you can
either have the author write files in CF conventions, or use NCML to
"fix up" the metadata.  The NetCDF Tools application has a very handy
tab for this -- you can load the file, select the NCML tab and then
edit the NCML to make the file structure adhere to CF conventions, and
then save the NCML.  You would then point the IDV at the NCML (it
contains a reference to the actual file).

Hope this helps.

tom

On 10/11/07, Brian Blanton <brian_blanton@xxxxxxxxx> wrote:
>
> Hi.  I have gridded (i.e., m X n) data in netCDF files, but the grid is
> rotated.  So, the lon/lat variables in the netCDf file are 2-d and not 1-d.
>
> Can I get these into IDV?
>
> Thanks,
> Brian
>
>
>
> <::><::><::><::><::><::><::><::>
> Brian O. Blanton
> Renaissance Computing Institute
> University of North Carolina at Chapel Hill
> 100 Europa Drive
> Suite 540
> Chapel Hill, NC, 27517
>
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-- 
Tom Whittaker
University of Wisconsin-Madison
Space Science & Engineering Center (SSEC)
Cooperative Institute for Meteorological Satellite Studies (CIMSS)
1225 W. Dayton Street
Madison, WI  53706  USA
ph: +1 608 262 2759