Jonathan,
Yes, I think your answer before is the answer now, but I'm just clear
on the details. Would you specify sea_surface_height above NAVD88
like this?
float zeta(y=1534, x=2122);
:standard_name = "sea_surface_height_above_reference_datum";
:grid_mapping = "Albers_Projection";
int Albers_Projection;
:grid_mapping_name = "albers_conical_equal_area";
:standard_parallel = 20.5, 27.5; // double
:longitude_of_central_meridian = -89.0; // double
:latitude_of_projection_origin = 24.0; // double
:false_easting = 0.0; // double
:false_north = 0.0; // double
:vertical_datum = 'urn:ogc:def:datum:epsg::5103'
Something like that?
On Tue, Feb 4, 2014 at 10:08 AM, Jonathan Gregory
<j.m.gregory at reading.ac.uk> wrote:
> 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
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
> ----- End forwarded message -----
> _______________________________________________
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--
Dr. Richard P. Signell (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
Received on Tue Feb 04 2014 - 11:32:51 GMT
