Dear Rich
Nothing further has been done in CF about this, but I'd be glad if it could be,
since it is often asked. I think there is no reason not to do something, since
there is an evident need, if we could only agree what should be done, and the
main problem is getting a sufficient understanding of these complexities. So
I can only repeat my last para in the email you point to:
> The discussion stalled because we didn't really understand what "vertical
> datum" means! ... [If this concerns the definition of the geoid], we should
> extend grid_mapping so it can identify the geoid by name, perhaps also giving
> a URN as you say. Unlike the ref ellipsoid, the geoid cannot be specified
> by metadata, as it's too complicated!
Is that the answer to your question of yesterday? i.e. would it suffice to
specify that by "geoid" in this data, "NAVD88" was meant? Of course, in other
datasets, geoid might mean a different definition. Specifying which geoid is
meant is not always possible (for instance in the case of model data), but we
could make it possible if that's useful. Is NAVD88 not a geoid name in your
example?
Best wishes
Jonathan
----- Forwarded message from "Signell, Richard" <rsignell at usgs.gov> -----
> 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
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----- End forwarded message -----
Received on Tue Feb 04 2014 - 08:08:06 GMT
