RE: Question about CDM

• To: "John Caron" <caron@xxxxxxxxxxxxxxxx>, "Pauline Mak" <pauline@xxxxxxxxxxxx>
• Subject: RE: Question about CDM
• From: "Woolf, A \(Andrew\)" <A.Woolf@xxxxxxxx>
• Date: Tue, 24 Apr 2007 18:10:06 +0100

WCS 1.1 does not yet support other than regular grids, though note there
is now a change proposal in (OGC document 06-160) to get irregular grids
(ISO 19123 CV_ReferenceableGrid in ISO-speak) into GML which should
help.

In my view it is crucial that conceptual models for grids remain unified
between GML, WCS, and ISO 19123.



> -----Original Message-----
> From: owner-thredds@xxxxxxxxxxxxxxxx 
> [mailto:owner-thredds@xxxxxxxxxxxxxxxx] On Behalf Of John Caron
> Sent: 24 April 2007 16:45
> To: Pauline Mak
> Cc: thredds@xxxxxxxxxxxxxxxx
> Subject: Re: Question about CDM
> 
> 
> 
> Pauline Mak wrote:
> > 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?
> 
> yes. 
> I think WCS 1.1 relaxes the regular spacing need, which will 
> implement later this year (probably).
> 
> 
> > 
> > Thanks,
> > 
> > -Pauline.
> > 
> > On 4/21/07, *Ethan Davis* <edavis@xxxxxxxxxxxxxxxx 
> > <mailto:edavis@xxxxxxxxxxxxxxxx>> wrote:
> > 
> >     Hi Pauline,
> > 
> >     Another resource for validating datasets against the CDM is 
> > available at
> > 
> >     http://motherlode.ucar.edu:8080/thredds/cdmValidate.html
> >     <http://motherlode.ucar.edu:8080/thredds/cdmValidate.html>
> > 
> >     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.
> > 
> >     Ethan
> > 
> >     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
> >      > pauline@xxxxxxxxxxxx <mailto:pauline@xxxxxxxxxxxx>
> >     <mailto:pauline@xxxxxxxxxxxx <mailto:pauline@xxxxxxxxxxxx>>
> > 
> >     --
> >     Ethan R. Davis                                
> Telephone: (303) 497-8155
> >     Software Engineer                             Fax:      
>  (303) 497-8690
> >     UCAR Unidata Program Center                  
> >     E-mail:    edavis@xxxxxxxx <mailto:edavis@xxxxxxxx>
> >     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
> > pauline@xxxxxxxxxxxx <mailto:pauline@xxxxxxxxxxxx>
> 
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• References:
  • Re: Question about CDM
    • From: John Caron