Dear Nan > DEPTH:reference=<R>; > where currently vetted values for R are "mean_sea_level", > "mean_lower_low_water", > "wgs84_geoid" and the default, "sea_level". > > DEPTH:coordinate_reference_frame="urn:ogc:crs:EPSG::5831"; or > HEIGHT:coordinate_reference_frame="urn:ogc:crs:EPSG::5829"; > 5831 and 5829 can be resolved at http://www.epsg-registry.org/ but are not > meant for human information. They're defined as 'depth (or height) > relative to instantaneous > water level, uncorrected for tide.'
The above is interesting. This and Rich's posting suggests that maybe part of the difficulty is a different organisation of concepts in CF. Maybe this is just my personal confusion, but I might not be the only one. The standard_names of depth and height in CF are defined as meaning vertical distance below and above "the surface". In stdnames, "the surface" means the bottom of the atmosphere. So these concepts include a vertical datum. There is no CF stdname for vertical distance above some surface to be specified in another part of the metadata. All the stdnames which somehow involve a special surface (like The Surface, the geoid, the tropopause, the top of the atmosphere, the bedrock) identify it in the stdname itself. However, some of these special surfaces might have to be more precisely defined in extra metadata to accompany the standard name. This can already be done for a reference ellipsoid, but not for a geoid. Best wishes Jonathan _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
