Dear Jonathan,
For years - even the odd decade - I believed 'direction' and 'direction_to' to be 100% synonymous for currents. However, I can recall current meter data delivered to BODC in the late 90s with channels labelled 'speed' and 'direction' where QC showed that the direction was in fact 'direction_from'. Enquiries revealed that the current meter data had been 'prepared' for assimilation into a metocean model based on meteorological conventions. Not a very common use case, especially as these days Cartesian rather than polar co-ordinates are more common, but I think its worth covering. Cheers, Roy. Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to [email protected]. Please also use this e-mail if your requirement is urgent. ________________________________ From: CF-metadata <[email protected]> on behalf of Jonathan Gregory <[email protected]> Sent: 02 June 2017 13:44 To: [email protected] Subject: Re: [CF-metadata] sea water speed and direction? Dear John and Roy direction_of_X is a construction in the standard name table, and I believe it's assumed it's a to_direction. For wind, which is the oldest vector in the table, we have to_direction and from_direction because of the potential confusion of e.g. westerly and westward wind. Is there a confusion in practice for sea water and sea ice? I mean, does anyone use "from" directions for these velocities? If there is a use-case, I agree we ought to distinguish. Best wishes Jonathan ----- Forwarded message from "Lowry, Roy K." <[email protected]> ----- > Date: Fri, 2 Jun 2017 09:20:26 +0000 > From: "Lowry, Roy K." <[email protected]> > To: John Maurer <[email protected]>, "[email protected]" > <[email protected]> > Subject: Re: [CF-metadata] sea water speed and direction? > > Dear John, > > > That's a good point about the ambiguity of 'direction_of_sea_water_velocity'. > As an observational oceanographer its built into my core program that > 'direction' means 'direction_to' for currents. I'm not alone here, which is > probably how the ambiguity got overlooked when the Standard Name was set up. > My suggestion for corrective action would be to alias > 'direction_of_sea_water_velocity' to 'sea_water_to_direction' whilst adding a > new Standard Name 'sea_water_from_direction'. I prefer your suggestions here > to the more verbose alternatives such as 'to_direction_of_sea_water_velocity'. > > > You could then use 'sea_water_speed' and 'sea_water_to_direction' for your > data as polar co-ordinates. You could also consider transforming to cartesian > co-ordinates and using 'eastward_sea_water_velocity' and > 'northward_sea_water_velocity' for the Standard Names. > > > I am opposed to the creation of separate 'surface' Standard Names unless > there is a case that the measured phenomenon is different. If you read the > definition of 'surface_eastward_sea_water_velocity' you will see that it > represents a different phenomenon to 'eastward_sea_water_velocity' because it > allows for the boundary between water body and atmosphere being either water > or ice. Consequently, unless there was a specific need to specify a > water-or-ice surface motion in terms of polar co-ordinates I would recommen > against adding the new 'surface' names that you suggest. > > > Cheers, Roy. > > > Please note that I partially retired on 01/11/2015. I am now only working 7.5 > hours a week and can only guarantee e-mail response on Wednesdays, my day in > the office. All vocabulary queries should be sent to [email protected]. > Please also use this e-mail if your requirement is urgent. > > > ________________________________ > From: CF-metadata <[email protected]> on behalf of John Maurer > <[email protected]> > Sent: 01 June 2017 20:37 > To: [email protected] > Subject: [CF-metadata] sea water speed and direction? > > Please provide guidance on which CF Standard Names to use for sea water > surface velocity. We will soon have a new buoy with an acoustic current meter > (ACM) that records speed (m/s) and direction (degrees) of the surface > currents. Are these the recommended CF Standard Names to attribute for these > measurement parameters?: > > * sea_water_speed > * direction_of_sea_water_velocity > > The latter does not indicate the "from" or "to" direction of the variable, > which concerns me. I am used to applying "wind_from_direction" or > "wind_to_direction" for wind measurements to solve this ambiguity. Thoughts > on replacing this with "sea_water_from_direction" and > "sea_water_to_direction"? > > Also, I note there are CF Standard Names that exist for > "surface_eastward_sea_water_velocity" and > "surface_northward_sea_water_velocity". I would expect and recommend the > addition of the following surface names: > > * surface_sea_water_speed > * surface_sea_water_from_direction > * surface_sea_water_to_direction > > Please advise. > Thanks!, > John Maurer > Data System Engineer > Pacific Islands Ocean Observing System (PacIOOS) > University of Hawaii at Manoa > ________________________________ > 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 > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata CF-metadata Info Page - mailman.cgd.ucar.edu Mailing Lists<http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata> mailman.cgd.ucar.edu This is an unmoderated list for discussions about interpretation, clarification, and proposals for extensions or change to the CF conventions. ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata CF-metadata Info Page - mailman.cgd.ucar.edu Mailing Lists<http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata> mailman.cgd.ucar.edu This is an unmoderated list for discussions about interpretation, clarification, and proposals for extensions or change to the CF conventions. ________________________________ This message (and any attachments) is for the recipient only. 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