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[THREDDS #KFL-964382]: issue with THREDDS not reading cf-netcdf file variables



Hi Sean:

> Hi,
> 
> I've sent this e-mail to John Caron earlier this month, but unfortunately
> haven't received a response, presumably because he's away or very busy,
> so I thought I'd try the general support service.

better to send here or to email group, as i can easily lose track of personal 
emails, as youve found out.

> 
> My name is Sean Gaffney and I work at the British Oceanographic Data
> Centre (BODC).
> 
> We at BODC use THREDDS version 4.3.18 to query CF-netCDF files that
> contain oceanographic numerical model data we are supplied with. I've
> recently been supplied with a set of model data which is causing THREDDS
> a problem. For some reason, THREDDS can't recognise two of the variables
> in the file (U and V - see ncdump of header below) and therefore, falls
> over whenever we try and perform any interaction with those variables.

the problem is that U,V have a coordinate "model_level_number" which we dont 
recognize as georeferencing. one can still do opendap and netcdf index access, 
but the services like WMS that want coordinates wont work. One work-around is 
to make it into a vertical coordinate by adding the attribute "positive" with 
value "up" or "down" (see CF docs for reference) to that coordinate. Ideally 
you can modify the files, but also you can wrap in NcML, esp for use in TDS:

<?xml version="1.0" encoding="UTF-8"?>
<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2"; 
location="G:/work/gaffney/NOCL_S12run420_1964_UV.nc">
  <variable name="model_level_number">
    <attribute name="positive" value="up" />
  </variable>
</netcdf>

To be complete, you would add a vertical coordinate transform, so the levels 
can be mapped to depth or pressure, eg the ones at 

http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#dimensionless-v-coord

Regards,

John


Ticket Details
===================
Ticket ID: KFL-964382
Department: Support THREDDS
Priority: Normal
Status: Closed


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