I assume surface_altitude is an important variable for providing the vertical location of measurements relative to a surface (as opposed to relative to a geoid -- notwithstanding the definition issue).
John On Sep 18, 2014, at 08:30, Signell, Richard <[email protected]> wrote: > Maybe a simpler approach would be to just adopt "platform_altitude" as > an alias for "surface_altitude" and suggest deprecating the use of > "surface_altitude"? > > On Thu, Sep 18, 2014 at 11:15 AM, John Graybeal > <[email protected]> wrote: >> Interesting that there is so little discussion of this language in the mail >> list, only in John Caron's 2011.09.16 mail on standard names for stations >> (which refers to words already in draft 1.6, I think) -- which came at the >> tail end of a long thread on platform names/IDs. >> >> From those words, I infer that the original drafter thought surface_altitude >> was just as good for describing platform location, as it was for describing >> observation location. I suspect the assumption was that any corresponding >> observations were at the same location as the platform. >> >> Since this is not always true, I'm with you that there should be a term >> platform altitude, and it should be the one used in this sentence. >> >> I hereby propose the standard name platform_surface_altitude (m), "Standard >> names for platform describe the motion and orientation of the vehicle from >> which observations are made e.g. aeroplane, ship or satellite. >> The surface called "surface" means the lower boundary of the atmosphere. >> Altitude is the (geometric) height above the horizontal reference surface." >> >> Note I've changed the standard wording of the _altitude definition, which >> generally says ".. above the geoid, which is the reference geopotential >> surface. The geoid is similar to mean sea level." This seems clearly in >> conflict with the definition of surface_altitude and this new term, and I >> think it should be changed in surface_altitude's definition too. >> >> I suppose if people agree with you and me, we need to do a Trac ticket for >> the corresponding change to the standard. >> >> John >> >> >> >> On Sep 18, 2014, at 06:40, Signell, Richard <[email protected]> wrote: >> >>> In the CF-1.6 and CF-1.7 draft doc, in section H.2, we have: >>> >>> "It is recommended that there should be station variables with >>> standard_name attributes " platform_name ", " surface_altitude " and “ >>> platform_id ” when applicable." >>> >>> Why is this "surface_altitude" instead of "platform_altitude"? >>> >>> In the ocean, we have lots of upward-looking Acoustic Doppler Current >>> Profilers (ADCP), where the instrument with transducer and other >>> sensors is located some distance below the ocean surface. While >>> velocity and other properties are measured in vertical bins above the >>> instrument (timeSeriesProfile), other properties like pressure and >>> temperature are measured at the instrument. >>> >>> Since the instrument is not at the surface, it seems misleading to use >>> the standard_name "surface_altitude" instead of "platform_altitude", >>> particularly when we already have "platform_name" and "platform_id". >>> >>> In this example CF_1.6 ADCP dataset: >>> >>> http://geoport.whoi.edu/thredds/dodsC/usgs/data2/rsignell/data/adcp/7201adc-a_cf16.nc.html >>> >>> the variable "platform_altitude" has a value of -10.4522 m: >>> http://geoport.whoi.edu/thredds/dodsC/usgs/data2/rsignell/data/adcp/7201adc-a_cf16.nc.ascii?platform_altitude >>> >>> but we are forced to use a standard_name of "surface_altitude". >>> >>> Why not "platform_altitude"? >>> >>> Thanks, >>> Rich >>> >>> -- >>> Dr. Richard P. Signell (508) 457-2229 >>> USGS, 384 Woods Hole Rd. >>> Woods Hole, MA 02543-1598 >>> _______________________________________________ >>> CF-metadata mailing list >>> [email protected] >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> > > > > -- > Dr. Richard P. Signell (508) 457-2229 > USGS, 384 Woods Hole Rd. > Woods Hole, MA 02543-1598 _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
