Hi. Regarding how ESRI represents vertical CRSs:
When ESRI specifies a particular vertical datum and doesn’t specify the ellipsoid, it is because the specified vertical datum specifies the ellipsoid. The fully realized definition still contains a specification of the ellipsoid that the geoid heights were measured against. I don’t think we should overload the add_offset attribute to do anything besides its meaning for rescaling. I’ll write more on this later, but there’s my quick $0.02 worth. Grace and peace, 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 11, 2014, at 8:59 AM, Jonathan Gregory <[email protected]> wrote: > Dear Rich > > Thanks for keeping this going. > >> In CF, we have some of these parameters of the vertical coordinate >> system specified with the "units" and "positive" attributes. And we >> already have "add_offset" that could be used for the vertical shift. >> >> So that just leaves the geoid-based "Vertical Datum" or spheroid-based >> "Datum", where the spheroid can be specified with parameters. > > In the agreed trac ticket 80 > https://cf-pcmdi.llnl.gov/trac/ticket/80 > we added several more attributes to grid mapping to describe reference > surfaces in ways analogous to CRS WKT. We already have attributes to name > and specify the reference ellipsoid (spheroid). As far as I can see, we need > only to add an attribute of geoid_name to Appendix F to identify the geoid. > Would that meet your requirement? Earlier discussions implied that CRS WKT > does not have a way to name the geoid specifically. > > Best wishes > > Jonathan > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
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