Great questions, John, glad you've started this conversation!
We're using the platform terms for some of the variables from
current meters and profilers deployed on surface moorings, so
our needs may be different from the satellite people.
Personally, I'd like to see the 'orientation' standard names
deprecated - in most definitions, heading, pitch, and yaw are all
components of orientation. And, among adcp users, this term is
often used in a more general sense, as an attribute, with values of
'upward-looking' or 'downward-looking'.
For the compass-related components, at least for surface or subsurface
platforms, we probably have to treat this like any other directional
parameter;
0 is north, and it's up to the user to specify whether they've done the
magnetic
correction to 'true north' or not.
Cheers - Nan
On 1/14/13 12:47 PM, John Graybeal wrote:
> From looking up the platform_orientation topic, I stumbled across all the
platform_ variables. I had a question and two concerns.
The question is about directional parameters. Where, if anywhere, is the
reference direction specified (and how can the data be interoperable if it is
not)? The units are degrees, but for platform_orientation, would that be from
true north, magnetic north, or some direction specified elsewhere? I imagine
there's a standard CF practice here.
A concern is that there are six terms that have exactly the same definition
(pitch angle, pitch rate, roll angle, roll rate, yaw angle, yaw rate). Once of
them, yaw angle, is arguably exactly the same thing as platform_orientation,
though maybe it depends on which authoritative source (and reference direction)
one uses.
A second concern is that the meaning of positive and negative values is not
defined, particularly for these 6 standard names. Perhaps that's a variant on
the reference direction question.
Has anyone dealt with these such that they see the obvious solution? If not,
what's the best way to make these useful, a suggestion on the mail list or a
trac ticket?
John
----------------
John Graybeal<mailto:[email protected]> phone: 858-534-2162
Product Manager
Ocean Observatories Initiative Cyberinfrastructure
Project:http://ci.oceanobservatories.org
Marine Metadata Interoperability Project:http://marinemetadata.org
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