This request has now been made by me of UDUNITS on general principle, but I think individuals could also express their desire as a way to move the ball forward.
John
On Aug 7, 2014, at 07:57, rhorne at excaliburlabs.com wrote:
> Dear Barry and David:
>
> For udunits support, send an email to support-udunits at unidata.ucar.edu.
>
>
>
> very respectfully,
>
> randy
>
>
>
> From: "Weiss, Barry H (398B)" <barry.h.weiss at jpl.nasa.gov>
> Sent: Thursday, August 07, 2014 10:06 AM
> To: "Moroni, David F (398M)" <David.F.Moroni at jpl.nasa.gov>, "Jonathan Gregory" <j.m.gregory at reading.ac.uk>
> Cc: "Niedfeldt, John C (398M-Affiliate)" <John.C.Niedfeldt at jpl.nasa.gov>, "CF Metadata List" <cf-metadata at cgd.ucar.edu>, "John Graybeal" <john.graybeal at marinexplore.com>, "cf-satellite at unidata.ucar.edu" <cf-satellite at unidata.ucar.edu>
> Subject: Re: [cf-satellite] [CF-metadata] normalized_radar_backscatter_coefficient
>
> Jonathan,
>
> As the data product engineer for the SMAP project, I second David's
> request.
>
> We are attempting to employ CF metadata in our products. This is not a
> challenge at level 2 and above where our products provide geophysical
> measure, but is a challenge at level 1, where our products provide
> instrument measurements.
>
> Please consider inclusion of dB units. That should include dB based on
> unit less measure, as well as dB relative to watts and volts.
>
> Thanks and Regards,
>
> Barry
>
>
> On 8/6/14 7:49 PM, "Moroni, David F (398M)" <David.F.Moroni at jpl.nasa.gov>
> wrote:
>
> >Hi Jonathan,
> >
> >Just as follow up from my last email, I noticed an online email exchange
> >where you had responded to a request to use units of dB (decibels) even
> >though it is not currently in the udunits database:
> >http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056572.html
> >
> >We also agree it would be wise to include dB in the udunits database, and
> >we will be applying these units for our scatterometer datasets.
> >
> >We hope to see this incorporated in the near future.
> >
> >Thanks again for your considerations.
> >
> >Cheers,
> >David
> >
> >On 8/5/14 7:24 PM, "Moroni, David F (398M)" <David.F.Moroni at jpl.nasa.gov>
> >wrote:
> >
> >>Hi John,
> >>
> >>We will incorporate these constant coordinate variables as you've
> >>recommended.
> >>
> >>Since during this 2+ month comment period we have not received any
> >>objections on our proposed inclusion of
> >>normalized_radar_backscatter_coefficient as a CF standard_name, we will
> >>now proceed with applying this as a standard_name for our relevant
> >>scatterometer datasets.
> >>
> >>On to our next concern: when will our proposed standard name become
> >>officially adopted into the CF standard name listing?
> >>
> >>Timing is not super critical, but considering what I perceive to be a
> >>consensus during this exchange of emails, we would at least like to
> >>obtain
> >>a statement of confirmation from the CF folks that this standard name
> >>will
> >>be adopted.
> >>
> >>A simple, brief email response from the chair or co-chair of this
> >>committee would suffice.
> >>
> >>Thank you again for your consideration and generous feedback.
> >>
> >>Cheers,
> >>David
> >>
> >>
> >>On 7/23/14 9:32 PM, "John Graybeal" <john.graybeal at marinexplore.com>
> >>wrote:
> >>
> >>>Hi David,
> >>>
> >>>Thanks for the question. Constant coordinate variables are hopefully not
> >>>a big deal -- they can be easily specified as scalar coordinate
> >>>variables, as noted in the example here:
> >>>http://cfconventions.org/Data/cf-convetions/cf-conventions-1.7/build/cf-
> >>>c
> >>>o
> >>>nventions.html#scalar-coordinate-variables.
> >>>
> >>>That's an example for analysis time and pressure level, but it's OK to
> >>>use coordinate variables for any critical reference variable. (Chapter
> >>>4:
> >>>"Coordinate types other than latitude, longitude, vertical, and time are
> >>>allowed." Incidentally, the text in reference [1] was proposed as a
> >>>replacement for that sentence in http://kitt.llnl.gov/trac/ticket/100,
> >>>which has been accepted but not implemented.)
> >>>
> >>>I had to search the archives to fully understand the motivation, here's
> >>>what I found (ooh, FAQ question!):
> >>> (1) To locate the data in an axis other than space or time. [1]
> >>> (2) To provide a consistent way to specify the value of a certain
> >>>other
> >>>parameter, or even multiple parameters; if the parameter is unvarying,
> >>>it
> >>>can be specified as a scalar. [2]
> >>>
> >>>So your declaration that both the radiation wavelength and scatter angle
> >>>were essential led to my suggestion. Adopting it standardizes the method
> >>>for citing the needed information (consistent with other standard names,
> >>>and across users of this standard name), thereby maximizing
> >>>interoperability.
> >>>
> >>>By all means reply further if this seems problematic, I'm at the edge of
> >>>my experience but others can jump in.
> >>>
> >>>John
> >>>
> >>>[1] On Apr 11, 2013, at 12:45, Jonathan Gregory
> >>><j.m.gregory at reading.ac.uk> wrote:
> >>>
> >>>> The commonest use of coordinate variables is to locate the data in
> >>>>space and
> >>>> time, but coordinates may be provided for any other continuous
> >>>>geophysical
> >>>> quantity (e.g. density, temperature, radiation wavelength, zenith
> >>>>angle of
> >>>> radiance, sea surface wave frequency) or discrete category (see
> >>>>Section 4.5,
> >>>> "Discrete axis", e.g. area type, model level number, ensemble member
> >>>>number)
> >>>> on which the data variable depends.
> >>>
> >>>
> >>>[2] On Dec 24, 2010, at 13:26, Jonathan Gregory
> >>><j.m.gregory at reading.ac.uk> wrote:
> >>>
> >>>> We quite often recommend, for instance in connection with particular
> >>>>standard names,
> >>>> that the value of a certain other parameter could be specified, e.g. a
> >>>> radiation_wavelength for radiative quantities. Scalar coord vars are a
> >>>>neat
> >>>> way to do this. They are something between multivalued coord vars and
> >>>> attributes in terms of function: easier than coord vars, and more
> >>>>powerful
> >>>> than attributes because they can themselves have attributes.
> >>>
> >>>[3]
> >>>
> >>>
> >>>On Jul 23, 2014, at 17:39, Moroni, David F (398M)
> >>><David.F.Moroni at jpl.nasa.gov> wrote:
> >>>
> >>>> Hi John (G),
> >>>>
> >>>> John (N) and myself are working together on this effort.
> >>>>
> >>>> Thanks for your inputs here.
> >>>>
> >>>> In general, I agree with the first part of your revision of the
> >>>>description, but I don't suggest including a reference to the
> >>>>coordinate
> >>>>values for the other standard names as you've suggested, namely
> >>>>"radiation_wavelength" and "scattering_angle", simply because this type
> >>>>of measurement assumes: 1) constant wavelength and 2) constant
> >>>>scattering angle. I simply don't follow your reasoning for why such
> >>>>coordinate values would be needed given the nature of these values
> >>>>being
> >>>>constant. Can you provide some rationale as to why we would want to
> >>>>list
> >>>>these as coordinate values?
> >>>>
> >>>> Cheers,
> >>>> David
> >>>>
> >>>> ==================================================
> >>>> David Moroni
> >>>> Ocean Wind and Scatterometry Data Engineer
> >>>> Physical Oceanography Distributed Active Archive Center
> >>>> Jet Propulsion Laboratory
> >>>> 4800 Oak Grove Dr
> >>>> M/S 158-242
> >>>> Pasadena, CA 91109
> >>>> Phone: 818.354.2038
> >>>> Fax: 818.353.2718
> >>>> ==================================================
> >>>>
> >>>> From: John Graybeal <john.graybeal at marinexplore.com>
> >>>> Date: Wednesday, July 23, 2014 3:52 PM
> >>>> To: "Niedfeldt, John C (398M-Affiliate)"
> >>>><John.C.Niedfeldt at jpl.nasa.gov>
> >>>> Cc: CF Metadata List <cf-metadata at cgd.ucar.edu>, David F Moroni
> >>>><David.F.Moroni at jpl.nasa.gov>
> >>>> Subject: Re: [CF-metadata] normalized_radar_backscatter_coefficient
> >>>>
> >>>>> Hi John (N),
> >>>>>
> >>>>> Thanks for the detailed explanation. I am convinced the new term is
> >>>>>distinct. I did not expect to redefine the old term unless one was
> >>>>>clearly a refinement of the other, which is not the case.
> >>>>>
> >>>>> I still am concerned about the description I think you are proposing
> >>>>>for this term ("normalized_radar_backscatter_coefficient is also
> >>>>>called
> >>>>>the normalized radar cross section, which are commonly used in the
> >>>>>microwave remote sensing community.") Based on your inputs, here is a
> >>>>>second attempt:
> >>>>>
> >>>>>> The fraction of incident power at a given wavelength that reaches a
> >>>>>>receiver, after reflection by a surface at a given reflection angle.
> >>>>>>(In microwave remote sensing this is also known as the 'normalized
> >>>>>>radar cross section' or 'sigma naught'.) Coordinate values for
> >>>>>>radiation wavelength and reflection angle should be given the
> >>>>>>standard
> >>>>>>names radiation_wavelength and scattering_angle.
> >>>>>
> >>>>> This description reflects: always 1 wavelength; always 1 backward
> >>>>>scattering angle; and that all lost power is included in the
> >>>>>coefficient, not simply the surface reflectance/absorption.
> >>>>>
> >>>>> If I correctly got your 3 points, the term "attenuated" applies, as
> >>>>>it
> >>>>>is used elsewhere in CF: "'The attenuated backwards scattering
> >>>>>function
> >>>>>includes the effects of two-way attenuation by the medium between a
> >>>>>radar source and receiver." Since I can't imagine needing an
> >>>>>unattenuated backscatter coefficient, the extra word seems unneeded
> >>>>>for
> >>>>>this name.
> >>>>>
> >>>>> John (G)
> >>>>>
> >>>>> On Jul 23, 2014, at 10:37, Niedfeldt, John C (398M-Affiliate)
> >>>>><John.C.Niedfeldt at jpl.nasa.gov> wrote:
> >>>>>
> >>>>>> Dear John et al,
> >>>>>> Here are three major distinctions between the
> >>>>>>surface_backwards_scattering_coefficient_of_radar_wave (old) and
> >>>>>>normalized_radar_backscatter_coefficient (new):
> >>>>>> ? The (old) definition has the default definition as being an
> >>>>>>integral over all wavelengths, but the radar backscatter coefficient
> >>>>>>is always measured using one wavelength (new) and must always be
> >>>>>>specified.
> >>>>>> ? The part about scattering radiation having no loss in energy in
> >>>>>>the (old) definition is not clear, but in practice and theory energy
> >>>>>>is always lost once the initial wave is transmitted (indeed, it is in
> >>>>>>part the loss due to the ground that we are measuring)(new).
> >>>>>> ? The backscatter in the (old) definition refers to summing all
> >>>>>>backwards scattering angles, where in remote sensing we look at just
> >>>>>>one backscatter angle (new).
> >>>>>> And yes, if the old variable pertains to the normalized radar cross
> >>>>>>section--which I believe it does not--then the transmitted wavelength
> >>>>>>and backscatter angle (elevation angle) should be required as they
> >>>>>>are
> >>>>>>essential to understanding the product and being able to correlate
> >>>>>>and
> >>>>>>verify data.
> >>>>>>
> >>>>>> So yes, we could change the old definition to meet the new needs,
> >>>>>>but
> >>>>>>it would require a change in base assumptions that would render any
> >>>>>>current data using that standard name as invalid. For these reasons
> >>>>>>and more, I believe we should make a new standard name. The
> >>>>>>definition
> >>>>>>I have provided is accurate and once approved additional attributes
> >>>>>>and values can be made required to suit all needs for those dealing
> >>>>>>with the normalized radar backscatter coefficient.
> >>>>>>
> >>>>>> Sincerely,
> >>>>>> John
> >>>>>>
> >>>>>> --
> >>>>>> John Niedfeldt
> >>>>>> Data Engineering
> >>>>>> PO.DAAC, JPL
> >>>>>>
> >>>>>> From: John Graybeal <john.graybeal at marinexplore.com>
> >>>>>> Date: Tuesday, July 22, 2014 at 3:53 PM
> >>>>>> To: JPL <John.C.Niedfeldt at jpl.nasa.gov>
> >>>>>> Cc: CF Metadata List <cf-metadata at cgd.ucar.edu>, "Moroni, David F
> >>>>>>(398M)" <David.F.Moroni at jpl.nasa.gov>
> >>>>>> Subject: Re: [CF-metadata] normalized_radar_backscatter_coefficient
> >>>>>>
> >>>>>> John, I think we (I, anyway) were waiting for a little more
> >>>>>>clarification as to what was needed. Sorry for that delay. I like
> >>>>>>the
> >>>>>>name itself, makes sense to me.
> >>>>>>
> >>>>>> Unless I am mistaken, from your email I infer that the meaning of
> >>>>>>this is a narrow case of
> >>>>>>surface_backwards_scattering_coefficient_of_radar_wave. That
> >>>>>>description is:
> >>>>>>> The scattering/absorption/attenuation coefficient is assumed to be
> >>>>>>>an integral over all wavelengths, unless a coordinate of
> >>>>>>>radiation_wavelength is included to specify the wavelength.
> >>>>>>>Scattering of radiation is its deflection from its incident path
> >>>>>>>without loss of energy. Backwards scattering refers to the sum of
> >>>>>>>scattering into all backward angles i.e. scattering_angle exceeding
> >>>>>>>pi/2 radians. Ascattering_angle should not be specified with this
> >>>>>>>quantity.
> >>>>>>
> >>>>>> I can't tell from the description if this item is different, so the
> >>>>>>description could use a little bit more meat to tease that out.
> >>>>>>Looking at your thread, I see this:
> >>>>>>
> >>>>>>> we are calculating sigma_naught which is the fraction of incident
> >>>>>>>power that is reflected by the surface. It is also very important in
> >>>>>>>scatterometry to record the angle of incidence as the sigma_naught
> >>>>>>>changes based on the incidence angle in addition to various other
> >>>>>>>parameters which are essential to being able to correlate data from
> >>>>>>>various scatterometers.
> >>>>>>
> >>>>>> So does it work for the description could say something like the
> >>>>>>following? This is still similar to the other standard name, so if
> >>>>>>there are specific things that make the distinction clear that would
> >>>>>>be important to add. ("This differs from surface_backwards_...")
> >>>>>>
> >>>>>>> The fraction of incident power that is reflected by the surface.
> >>>>>>>(In
> >>>>>>>microwave remote sensing this is also known as the 'normalized
> >>>>>>>radar
> >>>>>>>cross section' or 'sigma naught', when produced from one angle of
> >>>>>>>incidence and from one wavelength.) Scattering of radiation is its
> >>>>>>>deflection from its incident path without loss of energy. Backwards
> >>>>>>>scattering refers to the sum of scattering into all backward angles
> >>>>>>>i.e. scattering_angle exceeding pi/2 radians. A scattering_angle
> >>>>>>>should not be specified with this quantity. Coordinates of
> >>>>>>>radiation_wavelength and angle_of_incidence are used to specify
> >>>>>>>those
> >>>>>>>baseline parameters.
> >>>>>>
> >>>>>> I'm not sure about the last part -- if they are always needed these
> >>>>>>variables should be required.
> >>>>>>
> >>>>>> John
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> On Jul 22, 2014, at 14:49, Niedfeldt, John C (398M-Affiliate)
> >>>>>><John.C.Niedfeldt at jpl.nasa.gov> wrote:
> >>>>>>
> >>>>>>> Dear all,
> >>>>>>> Hello again! About two months back I sent in a request, which is
> >>>>>>>referenced below, in which I requested that we add the
> >>>>>>>?normalized_radar_backscatter_coefficient? in CF. Having heard
> >>>>>>>nothing to the contrary, and seeing as no other standards name match
> >>>>>>>our needs, we at PO.DAAC will be moving forward in implementing this
> >>>>>>>new standard name.
> >>>>>>>
> >>>>>>> As our newly reprocessed netCDF datasets shall soon serve as an
> >>>>>>>online replacement for existing datasets already in use by hundreds
> >>>>>>>of interdisciplinary scatterometry data users, we hope to likewise
> >>>>>>>hear back from you soon as to whether there is consensus on our
> >>>>>>>proposed standard name. If there is anything further we can do to
> >>>>>>>build community consensus on our proposed standard name, please let
> >>>>>>>me know.
> >>>>>>>
> >>>>>>> Sincerely,
> >>>>>>> John
> >>>>>>>
> >>>>>>> --
> >>>>>>> John Niedfeldt
> >>>>>>> Data Engineering
> >>>>>>> PO.DAAC, JPL
> >>>>>>>
> >>>>>>> From: Lauret Olivier <olauret at cls.fr>
> >>>>>>> Date: Friday, May 30, 2014 at 8:11 AM
> >>>>>>> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> >>>>>>> Cc: JPL <John.C.Niedfeldt at jpl.nasa.gov>
> >>>>>>> Subject: TR: normalized_radar_backscatter_coefficient
> >>>>>>>
> >>>>>>> Hi all,
> >>>>>>>
> >>>>>>> Just forwarding you some discussion we have with J. Niedfeldt about
> >>>>>>>some standard name for sigma naught variable. I thought the
> >>>>>>>available
> >>>>>>>?surface_backwards_scattering_coefficient_of_radar_wave? could be
> >>>>>>>used considering some changes in the definition [in short I wish we
> >>>>>>>could mix the description of sigma naught from radar altimetry with
> >>>>>>>the one from scatterometers]. But it seems that the quantities are
> >>>>>>>different enough to introduce a new standard name (see the message
> >>>>>>>below).
> >>>>>>>
> >>>>>>> Can we introduce ?normalized_radar_backscatter_coefficient? in CF?
> >>>>>>>
> >>>>>>> Thanks,
> >>>>>>>
> >>>>>>> Olivier
> >>>>>>>
> >>>>>>> De : Niedfeldt, John C (398M-Affiliate)
> >>>>>>>[mailto:John.C.Niedfeldt at jpl.nasa.gov]
> >>>>>>> Envoy? : jeudi 29 mai 2014 21:26
> >>>>>>> ? : Lauret Olivier
> >>>>>>> Objet : normalized_radar_backscatter_coefficient
> >>>>>>>
> >>>>>>> Dear Mr. Olivier,
> >>>>>>> After discussion with Dr. David Long of BYU and reviewing the
> >>>>>>>current definition with him it was determined that we do in fact
> >>>>>>>need
> >>>>>>>a new variable. In microwave remote sensing the normalized radar
> >>>>>>>cross section, sigma naught, is always produced from one angle of
> >>>>>>>incidence and from one wavelength. I understand the desire to
> >>>>>>>consolidate the number of standard names and to not have
> >>>>>>>duplication,
> >>>>>>>but adding this standard name would reduce confusion and error for
> >>>>>>>many I believe. It is also general enough that we can add attributes
> >>>>>>>to it in the future to allow further specification for various
> >>>>>>>endeavors. If you have any more questions feel free to contact me
> >>>>>>>and
> >>>>>>>thank you again for your assistance. We changed the standard_name to
> >>>>>>>be more descriptive.
> >>>>>>>
> >>>>>>> standard_name:
> >>>>>>> normalized_radar_backscatter_coefficient
> >>>>>>>
> >>>>>>> Definition:
> >>>>>>> normalized_radar_backscatter_coefficient is also called the
> >>>>>>>normalized radar cross section, which are commonly used in the
> >>>>>>>microwave remote sensing community.
> >>>>>>>
> >>>>>>> Canonical Units:
> >>>>>>> 1
> >>>>>>>
> >>>>>>>
> >>>>>>> Sincerely,
> >>>>>>> John Niedfeldt
> >>>>>>>
> >>>>>>>
> >>>>>>> Cliquez ici si ce message est ind?sirable (pourriel).
> >>>>>>>
> >>>>>>> _______________________________________________
> >>>>>>> CF-metadata mailing list
> >>>>>>> CF-metadata at cgd.ucar.edu
> >>>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >>>>>>
> >>>>>> _______________________________________________
> >>>>>> CF-metadata mailing list
> >>>>>> CF-metadata at cgd.ucar.edu
> >>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >>>>>
> >>>
> >>
> >
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