Re: [CF-metadata] Ambient light [Sec=Unclassified]
Thanks Miles, Having read around a bit more I agree that the term luminance implies visible (ie wavelengths detected by the human eye) light and so 'luminance_in_air' would work, providing a suitable definition is included. My straw man proposal for a definition would be 'A photometric measurement of the intensity of visible light that passes through or is emitted from a given area'. Anyone anything better? Cheers, Roy. -Original Message- From: Miles Jordan [mailto:miles.jor...@aad.gov.au] Sent: 11 January 2011 23:56 To: Lowry, Roy K. Cc: Jonathan Gregory; cf-metadata@cgd.ucar.edu Subject: RE: [CF-metadata] Ambient light [Sec=Unclassified] Thanks for your patience. I've asked what people think, and we have come up with a couple: surface_diffuse_luminance_of_shortwave_radiation_in_air or just luminance_of_shortwave_radiation_in_air. I don't think you can have luminance without diffuse reflection and I also don't think it can be a measurement of any other wavelength so it could be as simple as luminance_in_air. But I'll leave it up to the list to decide. Regards, Miles Lowry, Roy K. wrote: Hi Miles, I would confirm with somebody who undestands the data before making any decisions. Cheers, Roy. From: Miles Jordan [miles.jor...@aad.gov.au] Sent: 07 January 2011 12:07 To: Lowry, Roy K. Cc: Jonathan Gregory; cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] Ambient light [Sec=Unclassified] Quite possibly. I will have to take your recommendation on that as I am more on the software development side of things. Or shall I ask the people from my end that understand the data better? Sounds ok to me though. Regards, Miles Jordan mi...@milesjordan.com +61 424 879 668 On 07/01/2011, at 8:35 PM, Lowry, Roy K. r...@bodc.ac.uk wrote: Hi Miles, Should there be anything in the Standard Name to specify the wavelengths of light detected in the measurement e.g. luminous_intensity_of_shortwave_radiation_in air? Cheers, Roy. From: cf-metadata-boun...@cgd.ucar.edu [cf-metadata-boun...@cgd.ucar.edu] On Behalf Of Miles Jordan [miles.jor...@aad.gov.au] Sent: 07 January 2011 00:41 To: 'Jonathan Gregory' Cc: cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] Ambient light [Sec=Unclassified] Jonathan Gregory wrote: Dear Miles Just wondering if there is a standard name that I should use for ambient light in air measured in candles; I can't see one for ambient light, luminous intensity, or anything else I can think of. I don't think there is at present. Is candle the same as the SI unit candela? Please propose a standard name if you would like to. Yes, candela == candle. May I suggest luminous_intensity_in_air? Regards, Miles ___ Australian Antarctic Division - Commonwealth of Australia IMPORTANT: This transmission is intended for the addressee only. If you are not the intended recipient, you are notified that use or dissemination of this communication is strictly prohibited by Commonwealth law. If you have received this transmission in error, please notify the sender immediately by e-mail or by telephoning +61 3 6232 3209 and DELETE the message. Visit our web site at http://www.antarctica.gov.au/ ___ -- This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system. ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] CF data model
Hi Steve A high level description of the CF data model (pinning down concepts intuitively for readers as well as formal UML) would be a valuable addition to the document. (Maybe make this a trac ticket?) Agreed: we need both ... Bryan -- I'd like to make sure that the vocabulary is clear in interpreting your words. NetCDF is an ambiguous term in this context, because it is both a data model and a file format. I see the CF data model as a specialization of the netCDF data model, rather that a roll-your-own from scratch. To borrow the terminology from the de jure world, I see the netCDF-3 data model as a normative standard for CF. From a standard pov CF is stronger because it builds upon the netCDF data model. From your UML I infer that you are seeing things the same way. (It was the words that seemed ambiguous.) Clearly the existing CF definition builds from NetCDF, logically from the NetCDF data model ... as you say, that's the way it is, so that's the way I modelled it. Clearly the implementation is wrt the NetCDF data format. As Russ points out in his email, the extension to other formats could simply involve making sure one can implement the NetCDF parts of the data model in those formats ... It might be that with some slight tweaking of a *future* version of CF, expressed only as a data model, we can further simplify the implementation of CF in other formats. It may be that such simplilfication is unnecessary. Where it becomes interesting is when someone wants to consider using aspects of the netcdf4 data model directly within CF. Ideally we separate the efficient implementation from the underlying data model, but pragmatism usually requires a compromise. What seems a significant omission in this discussion, though, is the coupling to the CDM, which has already traversed much of this formal data modeling terrain. There is much to be gained in merging the two bodies of work. (And much to be lost by diverging.) This effort seems like the opportunity to pin down the areas where there is currently divergence. I think we start with what we have, agree on a precise description of that, then we evolve. I suspect we should see the CDM as a profile of CF ... (perhaps for our community, *the* profile, but for me, that would depend on the complete convergence of the logical properties of CSML and CDM). Cheers Bryan -- Bryan Lawrence Director of Environmental Archival and Associated Research (NCAS/British Atmospheric Data Centre and NCEO/NERC NEODC) STFC, Rutherford Appleton Laboratory Phone +44 1235 445012; Fax ... 5848; Web: home.badc.rl.ac.uk/lawrence ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
[CF-metadata] Ambient light [Sec=Unclassified]
Dear Miles I understand that luminance is in cd m-2 and applies to diffuse reflection or emission, as you say. A standard name not specifying wavelength would be assumed to refer to all wavelengths, I think: things are general unless they say they are specific. One thing is, luminance is directionally dependent. Do you have a particular direction in mind? Cheers Jonathan ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] CF data model
Dear Bryan (and Steve) Thanks for your diagram and comments. Yes, it would be good to sit down with you and see if we can reconcile our views expressed in words and pictures. :-) We can talk about that in other emails so that CF doesn't have to join in the discussion of our diaries. I may be disagreeing somewhat with you and Steve about whether the netCDF model should restrict us. It is where we started, but we may have constructed a logical model which has some more abstract concepts than netCDF does. For example, in netCDF we associate a dimension and a (Unidata) coord var by the equality of their names. In the CF model, the dimension and its coord var are part of the same thing, not two things with the same name. That is implied by your diagram too, which doesn't show dimensions on it. Also, in my model I have lumped together some things which CF does in different ways. For instance, I suggest that non-scalar formula terms are really auxiliary coord vars, and scalar coord vars and size-one coord vars are the same sort of thing. These are just my suggestions, which I am making because I think it might help how we think about further developments, including the representation of CF in other file formats (as you say), and the use of CF as a data model in an OO language. - I don't like the concept of a space construct. It's a new term to me which doesn't carry any useful attributes. I much prefer the use of object, which *is* a language neutral term (in data modelling). You don't like the term or you don't like the concept? If object is a language-neutral term, I'm happy to call it a space object instead. It corresponds to a data variable, but I don't call it that because I think everything in the logical model - all the metadata and the coordinates - are part of it. So it is data and the space in which the data resides. But if you haven't yet filled in the data, it is just the space. It is possible in memory that you might have a space object with no data array in it, but by the time you write it out to a CF-netCDF file, you must have a data variable. -I don't like central assumptions that are violated. Either we make it or we don't. You can make that assumption property of some attributes of space constructs. That is a good point. I suppose it means there is a higher level, perhaps a fragile and optional one, which relates some of the space objects. A higher level would also be needed to relate staggered grids and construct supergrids, as suggested by Balaji, but this hasn't been done in CF-netCDF yet. - I think text without pictures is just as unhelpful as pictures without text (my version :-). Let's see what we can do about that together. Best wishes Jonathan ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
