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Re: Question about CDM

Hi all,

Thanks for the help - through the second validator, I think I've found out what's wrong with the dataset.  Some of the axis doesn't have any values under the regular column.  I've written a little Java app that goes through a directory and find all nc files and checks that  a) it opens up as a GriddedDataset and then 2) the GridCoordSystem from the GriddedDataset isRegularSpatial().  Is this what it means by the WCS standard that it has to be gridded and regularly spaced?



On 4/21/07, Ethan Davis <address@hidden> wrote:
Hi Pauline,

Another resource for validating datasets against the CDM is available at


And I believe it is distributed with all TDS installations, so you could
try it locally at http://yourserver:port/thredds/cdmValidate.html

Which datasets can be served by the TDS depends on the service over
which you want to make them available. The HTTP bulk file download
service (/thredds/fileServer/) can serve any file. The OPeNDAP service
(/thredds/dodsC/) can serve any dataset that the netCDF-java library can
read (the file types that can be read are listed on the home page,
http://www.unidata.ucar.edu/software/netcdf-java/). The WCS service
currently only handles gridded data. The key here is that they have to
be recognized as gridded datasets by the netCDF-java library. The
library can recognize gridded data and the coordinates in the data using
a few different conventions. As Tom and/or Roy mentioned, CF is the
convention we recommend. The CDM validator above should give you more
clues on how well you dataset validates.

Hope that helps.


Pauline Mak wrote:
> Hi all,
> I'm currently setting up a THREDDS server to server our datasets.  The
> setup was fairly easy!  However, I'm running into problems with NetCDF
> files which doesn't conform to the "Common Data (Access) Model" - we
> want to serve all of our data through WCS (which comes for free with
> THREDDS data server!).  I've searched high and low for documentation
> on how to 'correct'  incompatible files. but failed to come up with
> anything.  Am I missing something? Should all NetCDF files "just work"
> with the NetCDF-Java 2.2 library?  I'm aware that files should be
> gridded and regular.  Am I understanding correctly that gridded means
> the files should have an x and y axis with optional z and t?   Is
> there a nice method to find out if a file is compatible and if it's
> not compatible, why it is so?
> My understanding of NetCDF file is rather shallow... so please bear
> with me if I'm asking a simple question...
> Thanks & cheers,
> -Pauline.
> --
> Pauline Mak
> Software Developer, Insight4
> Suite 2 / Level 1, 114 Murray St.
> Hobart, Australia 7000
> p:  (03) 6234 5203
> f:  (03) 6234 5603
> address@hidden <mailto:address@hidden>

Ethan R. Davis                                Telephone: (303) 497-8155
Software Engineer                             Fax:       (303) 497-8690
UCAR Unidata Program Center                   E-mail:    address@hidden
P.O. Box 3000
Boulder, CO  80307-3000                       http://www.unidata.ucar.edu/

Pauline Mak
Software Developer, Insight4
Suite 2 / Level 1, 114 Murray St.
Hobart, Australia 7000
p:  (03) 6234 5203
f:  (03) 6234 5603

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