Hi. I think there is still value in adding an attribute to the grid_mapping set where the name of the vertical datum can be supplied. The datums (data?) have “standard” names (not CF standard names). If you aren’t using a named vertical datum, you could specify either “none” (or just don’t specify the attribute) or “custom” if you are using a datum that hasn’t been given a name. I agree that the name alone is not necessarily sufficient, but it does provide a human-readable marker, whereas the WKT and URN approaches require further digging.
Just to be clear, I’m not advocating either/or with regards to the more rigorous approaches. A “vertical_datum” attribute that contains a human-readable name should be present in addition to one (or more) of the other approaches. 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: jbi...@cicsnc.org o: +1 828 271 4900 On Feb 7, 2014, at 10:25 AM, Hedley, Mark <mark.hed...@metoffice.gov.uk> wrote: > Hello Rich > > I think that using the WKT representation for vertical datum definitions is a > good approach > > As you have indicated, it is to be supported in CF 1.7 and provides a > controlled terminology set for this purpose. > > There is an example using the OS Newlyn datum in the draft spec which fits > quite nicely. > > I'd rather see us adopting WKT for complex issues like this than creating a > syntax for encoding CF grid_mapping attributes, there's a lot of prior art we > can benefit from. > > For example WKT enables me to specify more than just the EPSG code, which is > useful as not all datum instances are provided by EPSG > > mark > ________________________________________ > From: CF-metadata [cf-metadata-boun...@cgd.ucar.edu] on behalf of Signell, > Richard [rsign...@usgs.gov] > Sent: 04 February 2014 11:47 > To: CF metadata > Subject: [CF-metadata] Vertical datums (again) > > CF folks, > > On a telecon yesterday with a coastal inundation modeling group, one > of the PIs asked me how to handle vertical datums in NetCDF -- > specifically where to specify that the model bathymetry and water > levels were were relative to NAVD88. I wasn't sure how to reply. > > Was there any resolution to the 2nd half of this question asked back in 2011? > http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2011/054483.html > > I looked at the draft 1.7 spec, and the only vertical datum reference > info I found was the ability to specify VERT_DATUM in the new CRS > well-known-text (WKT) section: > http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.7-draft1/ch05s06.html#idp5644304 > > Is this how we should specify the vertical datum in CF, using VERT_DATUM in > WKT? > > Thanks, > Rich > -- > Dr. Richard P. Signell (508) 457-2229 > USGS, 384 Woods Hole Rd. > Woods Hole, MA 02543-1598 > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
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