Hi all,
Please forgive me for butting in late in a discussion. As an listener,
but not a participant, I find that I am not clear on the ground rules
for making decisions. Should CF standard names convey:
* how a measurement was made?
* for what purpose a parameter was measured?
Underlying this discussion is a discomfort with the notion that there
could be more than one variable in a CF file bearing the standard_name
"time". Is this a valid discomfort?
I'd note that observation communities such as OceanSites, Argo and GOSUD
that have adopted CF have regarded CF only as the basis for their
community standard. CF is not presumed to be sufficient as-is. They
have extended CF with many additional attributes and variables that
convey the subtler levels of semantics their community requires to
capture all of the details of a measurement type.
- Steve
P.S. Regarding the question below -- "which is the true time?" -- can
this be addressed through the use of the CF "coordinate = " attribute?
================================================================
Jonathan Gregory wrote:
> Dear John
>
>
>> Uh, to an observing systems/cyberinfrastructure person, ALL time
>> values have errors, _especially_ those from devices.
>>
>
> I think the point is, as Nan says, that the data user will want there to be one
> "time" which is to be regarded as coordinated, as the "true" time, in the sense
> that data values with the same coordinate of time are to be regarded as truly
> simultaneous. It is up to the data-writer to provide this coordinate if
> possible as they are typically better able to do it than the user. This one has
> the standard_name of "time".
>
> Regarding time_from_device, I would say that is not clear to me, because *all*
> times come from some device, even if it is an atomic clock determining the UTC
> standard! What about time_from_instrument. Would that be clearer than sensor?
> I think a sensor is a sampler in the existing name
> temperature_of_sensor_for_oxygen_in_sea_water
> but perhaps Nan or Roy could comment.
>
>
>> mission_elapsed_time is fine.
>>
> OK.
>
> My point about redundancy refers particularly to the time within year and day.
> Do you mean the device is giving you both the time (elapsed since some
> reference) and its components (time within year and day etc.). The time and
> its components are related by well-defined arithmetic. Do you want to record
> them all separately? If so, why? Perhaps for completeness, to be on the safe
> side?
>
> Thanks for the discussion. Best wishes
>
> Jonathan
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>
--
Steve Hankin, NOAA/PMEL -- Steven.C.Hankin at noaa.gov
7600 Sand Point Way NE, Seattle, WA 98115-0070
ph. (206) 526-6080, FAX (206) 526-6744
"The only thing necessary for the triumph of evil is for good men
to do nothing." -- Edmund Burke
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