[CF-metadata] example of sea_surface_wave_directional_variance_spectral_density

Hattersley, Richard richard.hattersley at metoffice.gov.uk
Thu Aug 30 09:51:59 MDT 2012


Hi Roy,

There are some fairly explicit statements in chapter 9 that mean
treating 'z' as frequency would break the convention.

>From 9.1:
	profile => "an ordered set of data points along a vertical line
..."

	"The spatial coordinate z refers to vertical position."

And it's not clear that you could add an additional dimension for the
frequency. (That said, it's also not completely clear that you
shouldn't.)

Looks like CF would benefit from your BODC feature types.

Regards,

Richard Hattersley  AVD  Iris Technical Lead
Met Office  FitzRoy Road  Exeter  Devon  EX1 3PB  United Kingdom
Tel: +44 (0)1392 885702  Fax: +44 (0)1392 885681
Email: richard.hattersley at metoffice.gov.uk  Website:
www.metoffice.gov.uk
 

> -----Original Message-----
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] 
> On Behalf Of Lowry, Roy K.
> Sent: 29 August 2012 16:26
> To: Ellyn Montgomery
> Cc: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] example of 
> sea_surface_wave_directional_variance_spectral_density
> 
> Hi again,
> 
> Within BODC, we address your concerns by having a much richer 
> set of feature types that include concepts like 
> timeSeriesSpectrum to indicate that the z-axis is non-spatial 
> and so give display clients a bit more help.  However, I 
> think that with the right parameter attribute semantic 
> information and the CF feature types we should be OK in SeaDataNet.
> 
> My thinking so far has been confined to non-directional 
> spectra.  I can't see how directional spectra could be 
> handled in CF without specification of an additional feature 
> type, but (not for the first time) I might be 
> misunderstanding something in John's view of feature types.
> 
> Cheers, Roy. 
> 
> -----Original Message-----
> From: Ellyn Montgomery [mailto:emontgomery at usgs.gov] 
> Sent: 29 August 2012 15:47
> To: Lowry, Roy K.
> Cc: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] example of 
> sea_surface_wave_directional_variance_spectral_density
> 
> Roy-
> I'm glad that it's on your plate!
> 
> Conceptually, I am a bit uncomfortable with having frequency 
> as Z since 
> many of us think of Z as depth/altitude.  Having frequency as 
> Z fits the 
> shapes allowed, but I wonder what confusion it would start.  
> Are there 
> ways for clients to identify Z as a non-depth content?  Is it 
> as simple 
> as calling the Z coordinate "frequency" instead of "depth", and then 
> clients would be able to know what to do?
> 
> Then of course the direction component would need to be 
> wedged into the 
> coordinate system somehow.  Such fun!
> 
> Looking forward to the discussion!
> Ellyn
> 
> 
> On 08/29/2012 09:54 AM, Lowry, Roy K. wrote:
> > Hi Ellyn,
> >
> > Encoding wave spectra in a CF-compliant manner is an issue 
> that I plan to address on behalf of SeaDataNet in the next 
> month or so.  The point I'd reached in thinking this through 
> was to use the timeSeriesProfile feature type with frequency 
> as the z co-ordinate.  I think this OK, but if not I'm sure 
> somebody on this list will shout.
> >
> > I prefer single-value vectors rather to scalars because it 
> opens the way to packaging multiple instances into a single 
> NetCDF file.
> >
> > Cheers, Roy.
> >
> > -----Original Message-----
> > From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] 
> On Behalf Of Ellyn Montgomery
> > Sent: 28 August 2012 15:04
> > To: cf-metadata at cgd.ucar.edu
> > Subject: [CF-metadata] example of 
> sea_surface_wave_directional_variance_spectral_density
> >
> > Hello folks-
> >
> > We want our wave data observations to be CF compliant, with the
> > dimensions and representation of time correct.  I believe 
> the data we
> > collect fits somewhere under Discrete Samples, since we end 
> up with a
> > time series of wave spectra from our stationary, 
> bottom-mounted acoustic
> > instruments.  I couldn't find how the file might look in the 1.6
> > conventions document or appendices, so could someone please 
> direct me to
> > an example dataset that includes some wave spectra?  Help with which
> > featureType should be used would also be appreciated.
> >
> > The Standard Name table says the dimension order should be
> > S(t,x,y,f,theta).  Since our data is from a point 
> observation (lat and
> > lon are size (1)), can the X,Y dimensions be dropped, or 
> are they needed
> > as place-holders?
> >
> > Thanks very much for the help!
> > Ellyn
> >
> 
> 
> -- 
> Ellyn T. Montgomery, Oceanographer and Data Manager
> U.S. Geological Survey
> Woods Hole Coastal and Marine Science Center
> 384 Woods Hole Road, Woods Hole, MA 02543-1598
> (508)457-2356
> 
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