[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Question about CDM

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: Re: Question about CDM
  • Date: Thu, 26 Apr 2007 14:11:01 -0600
Hi Pauline:

I think Andrew's the expert on this, sounds like WCS 1.1 does not yet support 
irregular x,y coordinates. WCS 1.1.0 
(http://www.opengeospatial.org/standards/wcs) is final, but there are ongoing 
efforts to improve the next version (1.2 i suppose).

The GALEON document was written before the spec was final, so it is not 
authoritative.

Pauline Mak wrote:

Hi John & Andrew :)

Thanks for the insight into WCS - I must confess I'm not very
geographically-minded and find the standard document somewhat daunting!

I'm still a little confused though... So is WCS 1.1 still in
development?  And that, once it's publish, it will include irregular
grid?  I've also found an interesting document here:
http://www.unidata.ucar.edu/projects/THREDDS/GALEON/WCSnetCDFencoding.htm and 
it seems to imply that WCS can support irregular grid.  I could have 
misunderstood what it meant about row 6...  Some clarification would be much 
appreciated :)

Cheers,

-Pauline.

On Tue, 2007-04-24 at 18:10 +0100, Woolf, A (Andrew) wrote:

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: address@hidden [mailto:address@hidden] On Behalf Of John Caron 
Sent: 24 April 2007 16:45
To: Pauline Mak
Cc: address@hidden
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* <address@hidden <mailto:address@hidden>> 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
     > address@hidden <mailto:address@hidden>
    <mailto: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 <mailto: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
address@hidden <mailto:address@hidden>

==============================================================
=================
To unsubscribe thredds, visit:
http://www.unidata.ucar.edu/mailing-list-delete-form.html
==============================================================
=================



===============================================================================
To unsubscribe thredds, visit:
http://www.unidata.ucar.edu/mailing-list-delete-form.html
===============================================================================



===============================================================================
To unsubscribe thredds, visit:
http://www.unidata.ucar.edu/mailing-list-delete-form.html
===============================================================================