[CF-metadata] fixed sensors, depth, datum

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 11 Sep 2008 17:36:51 +0100

Dear Dale

It seems none of us who has so far contributed claims to be an expert. If any
experts are listening in, they are welcome to comment!

> The recommendation is that I request a few new standard names.
> Standard names like height_above_geoid and
> height_above_reference_ellipsoid seem appropriate
Yes.

> Can one use in any variable an
> attribute normally found in the crs variable such as
> vertical_datum_name? For example
> float ht_wgs84
> ht_wgs84:long_name = "Height referenced to WGS84";
> ht_wgs84:standard_name = height_above_reference_ellipsoid
> ht_wgs84:vertical_datum_name = "World Geodetic System 1984"
vertical_datum_name is not a CF attribute. CF doesn't preclude other attributes
being included, so that's fine, but software implementing CF would not use
the attribute.

In my earlier posting, I suggested that we could define the geoid by
extending the grid_mapping variable (CF 5.6). There is currently not a standard
CF way to name the geoid or ellipsoid, but the ellipsoid can be defined
geometrically by the grid_mapping variable. Any solution to this would need
an addition to the CF standard.

> One option is to propose more specific standard names as suggested by
> Jon. E.g. height_above_wgs84 and height_above_navd88. Do you think
> that this is a viable direction?

I don't like that so much myself, because I feel that heights above various
geoids are the same geophysical quantity, so they should not have different
standard names. It seems better to me to add something to the convention,
especially as this has been raised before but not solved.

In your example it appeared that you wanted to record the offsets between
the geoid and the various tidal datums. My suggestion for that is to put them
in separate data variables and give them standard names (to be proposed) of
the form height_above_geoid_of_TIDAL_DATUM.

> Finally, how do I go about suggesting new standard names?
By proposing them to this email list, with canonical units and brief
description.

Best wishes

Jonathan
Received on Thu Sep 11 2008 - 10:36:51 BST