[CF-metadata] water level with/without datum

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 22 Feb 2010 19:01:40 +0000

Dear Jeff et al

About
>water_level_with|above_reference_datum
>water_level_without_reference_datum
I'd like to make some suggestions:

* Since we don't have a convenient word for river, lake or sea, perhaps we
should have separate names for each of them i.e. sea_surface_height,
lake_surface_height and river_surface_height. All these terms are in use, often
in connection with altimetry. Obviously the same duplication (or triplication)
could occur with other sea-related names, but we have not had a great demand
for terms related to lakes and rivers up to now. Even if we did, it would
not be an unmanageable expansion of the standard name table. There are
currently 284 standard names containing the word "sea".

* If the datum is an arbitrary local benchmark, then I think a name of
sea/lake/river_surface_height_above_reference_datum would be fine. If the
datum itself needs to be located, we could have standard names for that such
as sea/lake/river_surface_reference_datum_altitude.

* If the datum is a quantity which could be regarded as a continuous function
of location, I think it should be identified in the standard name, as in the
existing sea_surface_height_above_geoid. Other standard names would thus be
needed for sea_surface_height_above_mean_high_water etc. We also have an
existing name of sea_surface_height_above_reference_ellipsoid. Here, the
ellipsoid is not identified, but it can be with other CF metadata. I think
that's OK because the geophysical intention of the reference ellipsoid is
always the same, so this is in a sense a matter of measurement rather than
the quantity itself. By contrast, mean high water is a different geophysical
concept from the geoid.

Best wishes

Jonathan
Received on Mon Feb 22 2010 - 12:01:40 GMT