Hi all -
Here's the description of the error_velocity recorded by an ADCP; this text
is taken from the US-IOOS current QC manual that was recently published,
at
http://www.ioos.noaa.gov/qartod/currents/qartod_currents_manual.pdf.
> Error velocity is a key QC parameter that derives from the 4-beam
> geometry of an ADCP. Each pair of opposing beams provides one
> measurement of the vertical velocity and one component of the
> horizontal velocity, so there are two independent measurements of
> velocity that can be compared. If the flow field is homogeneous, the
> difference between these velocities will average to zero. The error
> velocity can be treated as an indication of errors in the horizontal
> velocity measurements. This test is applied to each depth bin.
I wonder if a single standard name or modifier could be used for many types
of non-standard error variables, with an attribute identifying the type
of calculation
used to generate the value.
Regards - Nan
On 7/3/13 9:57 AM, Jonathan Gregory wrote:
> Dear all
>
> OK, I agree that if it's useful to compare them, then they should be described
> in a standardised way.
>
> Why is this *not* a standard error? I suppose that to be described as a
> standard error it should be a number you could regard as the standard deviation
> of the true value around the stated value. If it's not that, are there other
> ways you would use such a number?
>
> Best wishes
>
> Jonathan
>
> ----- Forwarded message from John Graybeal <john.graybeal at marinexplore.com> -----
>
>> From: John Graybeal <john.graybeal at marinexplore.com>
>> Date: Mon, 1 Jul 2013 14:19:30 -0700
>> To: ngalbraith at whoi.edu
>> X-Mailer: Apple Mail (2.1508)
>> CC: cf-metadata at cgd.ucar.edu
>> Subject: Re: [CF-metadata] Fwd: how to represent a non-standard error
>>
>> Yes please, I've wanted the ability to specify something like "error_estimate" for some time too. Even if the calculations are not done in exactly the same way -- they could even be off by an order of magnitude -- being able to compare them is meaningful. And it's extremely valuable to be able to answer the query "Which variables have error estimates?"
>>
>> So if we can some up with a standard way to represent this it will be extremely helpful.
>>
>> John
>>
>> On Jul 1, 2013, at 13:00, Nan Galbraith <ngalbraith at whoi.edu> wrote:
>>
>>> I think that these are fairly important QC checks for wind and current
>>> data, and that they deserve to have standard names to make them
>>> more useful. Although the algorithms may differ between instruments,
>>> and may even be proprietary, these variables are often the most useful
>>> way to provide information about the reliability of the geophysical
>>> measurements.
>>>
>>> I had asked about the best way to label this parameter for ADCP data
>>> several years ago, but I wasn't able to explain why standard_error wasn't
>>> appropriate (it's a little outside my field).
>>>
>>> Could we use a standard name modifier like 'instrument_error',
>>> or even just 'error', to convey the meaning of instrument-provided
>>> error information? That would be much simpler than requesting a
>>> name for each instrument type (although I suppose there may be
>>> only a handful of those).
>>>
>>> Thanks - Nan
>>>
>>> On 7/1/13 1:10 PM, Jonathan Gregory wrote:
>>>> Dear Randy
>>>>
>>>> If it is very product-specific, is it really a geophysical quantity which needs
>>>> a standard name? I mean, are there data from several sources for this quantity
>>>> which should be regarded as comparable, and which therefore should have a
>>>> common standard name?
>>>>
>>>> If the answer is Yes, then I would suggest you propose a standard name which
>>>> explicit names the algorithm, like e.g. isccp_cloud_area_fraction.
>>>>
>>>> Best wishes
>>>>
>>>> Jonathan
>>>>
>>>> ----- Forwarded message from "rhorne at excaliburlabs.com"<rhorne at excaliburlabs.com> -----
>>>>
>>>>> From: "rhorne at excaliburlabs.com"<rhorne at excaliburlabs.com>
>>>>> To: cf-metadata at cgd.ucar.edu
>>>>> Date: Mon, 1 Jul 2013 08:28:15 -0400
>>>>> Subject: [CF-metadata] how to represent a non-standard error
>>>>>
>>>>>
>>>>>
>>>>> Folks: the GOES-R ground system generates a derived motion winds product.
>>>>> Accompaning each wind speed& direction in the product is the amount of
>>>>> error associated withe the vector. This error is not a standard_error, but
>>>>> an error estimate based on a custom algorithm. Because this is not a
>>>>> standard_error, it would seem that using a standard_error standard_name
>>>>> modifier would be misleading. Any thoughts on how to represent this
>>>>> product-specific error in the NetCDF file ? (The best idead I could come up
>>>>> with so far is to establish an ancillary data relationwhip between the wind
>>>>> speed/direction variables and the error variable, and use the error
>>>>> variable's long_name to describe the error) very respectfully, randy
>>>>> _______________________________________________
>>>>> CF-metadata mailing list
>>>>> CF-metadata at cgd.ucar.edu
>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>>> ----- End forwarded message -----
>>>> _______________________________________________
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>>>
>>> --
>>> *******************************************************
>>> * Nan Galbraith (508) 289-2444 *
>>> * Upper Ocean Processes Group Mail Stop 29 *
>>> * Woods Hole Oceanographic Institution *
>>> * Woods Hole, MA 02543 *
>>> *******************************************************
>>>
>>>
>>>
>>> _______________________________________________
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>>> CF-metadata at cgd.ucar.edu
>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>> ------------------------------------
>> John Graybeal
>> Senior Data Manager, Metadata and Semantics
>>
>> T +1 (408) 675-5545
>> F +1 (408) 616-1626
>> skype: graybealski
>>
>> Marinexplore
>> 920 Stewart Drive
>> Sunnyvale, CA
>>
>>
>>
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> ----- End forwarded message -----
> _______________________________________________
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>
--
*******************************************************
* Nan Galbraith Information Systems Specialist *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 (508) 289-2444 *
*******************************************************
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