Dear Jim Is it a trajectory feature using the discrete sampling geometry convention of section 9? In that case it is required that there should be a nominal longitude, latitude and time for each observation along the trajectory. However you could also supply data variables of longitude and latitude with cell_methods along the same trajectory, and these data variables could be named by the coordinates attribute of other data variables (serving as auxiliary coordinate variables), to provide a more precise indication of location, as in section 9.5.
Yes, the cell_methods would be "cell methods where there are no coordinates" of section 7.3.4 since you don't have longitude and latitude dimensions. It is permitted to specify "area:" for a cell method even if there are no horizontal dimensions specified. Cheers Jonathan ----- Forwarded message from Jim Biard <[email protected]> ----- > Jonathan, > > What I mean is, this is not gridded data. The operations being performed > (mean latitude, etc) are over a geographic region that is not described > anywhere in the file, which is the region considered to be the extent of the > weather system. So, you are saying that this trajectory case falls under the > ?Cell methods when there are no coordinates? case, is that right? > > Jim > > Visit us on > Facebook Jim Biard > Research Scholar > Cooperative Institute for Climate and Satellites NC > North Carolina State University > NOAA's National Climatic Data Center > 151 Patton Ave, Asheville, NC 28801 > e: [email protected] > o: +1 828 271 4900 > > > > > On Mar 4, 2014, at 9:30 AM, Jonathan Gregory <[email protected]> > wrote: > > > Dear Jim > > > >> Even though there are no cells? That?s the part that I?m feeling confused > >> about. > > > > Sorry, I'm not sure why you say there are no cells. "Cell" does not imply > > any > > number of spatial dimensions - is that the problem? It means the portion of > > the domain, of whatever dimensionality, which is represented by a particular > > data value. The cell_methods attribute indicates how that data value > > represents > > unrecorded variability of the quantity represented within the cell. > > > > Best wishes > > > > Jonathan > > > >> On Mar 3, 2014, at 1:22 PM, Jonathan Gregory <[email protected]> > >> wrote: > >> > >>> Dear Jim > >>> > >>> Yes, I think such an approach is applicable. Any data variable can have > >>> cell_methods and any data variable could be used as an aux coord variable. > >>> Although unusual, I don't see a reason not to have data variables of > >>> latitude > >>> and longitude, qualified by cell_methods, if required. > >>> > >>> Best wishes > >>> > >>> Jonathan > >>> > >>> ----- Forwarded message from Jim Biard <[email protected]> ----- > >>> > >>>> Subject: Re: [CF-metadata] can a cell method be an attribute of an > >>>> auxiliary > >>>> coordinate variable ? > >>>> From: Jim Biard <[email protected]> > >>>> Date: Fri, 28 Feb 2014 14:01:24 -0500 > >>>> CC: [email protected] > >>>> To: Jonathan Gregory <[email protected]> > >>>> X-Mailer: Apple Mail (2.1874) > >>>> > >>>> Jonathan, > >>>> > >>>> So, I?ve got a broader question. We have a case in hand with trajectory > >>>> data for a physically extensive weather system. Two data variables are > >>>> the mean longitude and latitude of the system, which we are treating as > >>>> the auxiliary coordinate variables. Other data variables contain > >>>> measurements such as maximum latitude at the mean longitude, etc. Are > >>>> cell_methods applicable in this case? There is no grid, so the cell > >>>> would be the area covered by the system, and the extents of this area > >>>> are not described. > >>> _______________________________________________ > >>> CF-metadata mailing list > >>> [email protected] > >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > _______________________________________________ > > CF-metadata mailing list > > [email protected] > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
