There is an interesting general point raised here by the statement 'a standard name for each reference datum would be a
little bit excessive'. If the specific reference datum isn't held in the standard name then the information needs to be in another standardised location in the CF attributes or the data are not fully decribed by the metadata. I remember the issue of datums came up before with regard to CF, but can't remember if it was ever resolved.
Cheers, Roy.
>>> Olivier Lauret <olauret at cls.fr> 8/22/2006 12:26 pm >>>
Dear Tom,
The fact is that MSL, MLLW, NAVD88.. especially concern tide gauges,
coastal oceanography - among the applications, and do not really apply to
satellite altimetry. Of course I only focused on altimeter data, that
usually refer to, let's say, 4 different reference surfaces: the reference
ellipsoid (it can be WGS84 or any other), a mean along-track profile or a
mean sea surface, and (indirectly) the geoid.
But I agree with you: a standard name for each reference datum would be a
little bit excessive.
At the same time "sea_surface_height_above_sea_level",
"sea_surface_height_above_geoid" were already availble in the standard
names table, and none of them could "include" or be compared to altimeter
sea_surface_height_above_reference_ellipsoid, because beyond the reference
datum, the meaning is different in terms of physical processes to be
considered. Then it raises the question of how we define the reference
surfaces.
One one hand, if the whole entire sea surface height parameters (in situ,
tide gauges..) could refer to {"sea_surface_height_above_sea_level",
"sea_surface_height_above_geoid"}, except satellite altimetry, maybe it is
possible for us to introduce the missing altimeter dedicated standard names?
On the other hand, we could also take advantage of the situation by
introducing some new standard names, more general, like
"sea_surface_height_above_reference_surface" and
"sea_surface_height_above_reference_profile", that would include all sea
surface height kinds of parameters, and all the reference datums?
For "sea_surface_height_above_reference_surface", the reference surface
could be a mean sea surface, a reference ellipsoid, or the geoid, that
could be specified as attributes.
For "sea_surface_height_above_reference_profile", the reference profile
could be a mean sea level, a mean profile etc, defined as attributes as well.
I don't know. That depends on the fellings of the ocean/climate users
community, but the discussion is open.
Best regards
Olivier Lauret
CLS Space Oceanography Division
Data Information and Diffusion
8-10 rue Hermes,
31526 Ramonville-St-Agne, Cedex, France
Email: olivier.lauret at cls.fr
Tel: (+33) (0) 561 39 48 51
Fax:(+33) (0) 561 39 48 51
Internet:
http://www.cls.fr
http://www.aviso.oceanobs.com/
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Received on Tue Aug 22 2006 - 05:45:20 BST
