[Esip-documentation] on documenting instrument and platform metadata

[Aaron Sweeney]

Thanks very much for the guidance, John.  I think I may stick with the 
NODC or OceanSites platform and instrument variables to define the 
particular instances.

That being said, for my two use cases, I think I can still capture the 
type of platform and instrument in the ACDD global attributes. This 
amounts to:

     :platform = "DART"
     :platform_vocabulary = "NASA/GCMD Platform Keywords. Version 8.0"
     :instrument = "BOTTOM PRESSURE GAUGES"
     :instrument_vocabulary = "NASA/GCMD Instrument Keywords. Version 8.0"

and

     :platform = "COASTAL STATIONS"
     :platform_vocabulary = "NASA/GCMD Platform Keywords. Version 8.0"
     :instrument = "TIDE GAUGES"
     :instrument_vocabulary = "NASA/GCMD Instrument Keywords. Version 8.0"

Cordially,
Aaron

On 03/16/2015 02:43 PM, John Graybeal wrote:
> What great questions!  The following thoughts are my own, and are 
> unrelated to my previous ACDD activities.
>
> Clearly some data files will have data from multiple platforms and 
> instruments; whereas others will get all their variables from a single 
> platform/instrument; and some will have data so heavily processed as 
> to be barely traceable to the source platforms/instruments. Each of 
> the specifications is oriented toward somewhat different scenarios, 
> and none of them are yet great at representing all the scenarios.
>
> Let's consider ACDD first. Note that this specification provides 
> _recommendations_ for attributes, not _requirements_; and the platform 
> and instrument attributes are only 'Suggested'. These give a 
> broad-brush categorization of the platform(s) or instrument(s) that 
> collected a data set; if it seems reasonable to specify that 
> information for the whole data set, use these attributes to do so. (If 
> it isn't useful/applicable, then don't worry about these attributes.) 
>  The most precise way to give that info is to use a controlled 
> vocabulary (see 
> https://marinemetadata.org/references?filter0=**ALL**&filter1%5B%5D=129&filter1%5B%5D=141 
> <https://marinemetadata.org/references?filter0=**ALL**&filter1[]=129&filter1[]=141> for 
> a partial list of vocabularies), and typically I'd expect a type 
> vocabulary here (with e.g. "CTD", "Mooring") not a specific instance.
>
> If you *are* following ACDD, I don't recommend putting the names of 
> variables containing information on platforms and instruments in the 
> global attributes 'platform' and 'instrument'. Without ACDD describing 
> that as a possibility, it's highly unlikely any software will know how 
> to treat that, and some people will get confused too. The existence of 
> the variables will be pretty self-explanatory, so just leave out those 
> ACDD attributes. (I see this conflicts with NODC and OceanSITES 
> recommendations, to my surprise; perhaps others will offer another 
> view here.)
>
> Whether to put the information in a global instrument variable, or 
> attributes of each data variable, or both, seems to me a matter of 
> circumstances and taste. Let's stipulate the best solution is 
> human-recognizable, computer-parseable, extensible, and unambiguous. 
> Thus, global attributes are inadequate. Assuming a sophisticated data 
> system 5 years from now would look in both variables and data 
> attributes, then the model of 'one variable per instrument or 
> platform', and association from the data variables to those variables 
> or platforms seems best.
>
> But given that the examples in each of the different profiles still 
> seems inconsistent, likely you should follow the guidance most close 
> to your work. If you aren't particularly close to any of them, I'd do 
> it a bit differently still. But I'll hold that thought unless you want 
> to extend the discussion in that direction.
>
> John
>
>
> On Mar 16, 2015, at 11:56, Aaron Sweeney via Esip-documentation 
> <esip-documentation at lists.esipfed.org 
> <mailto:esip-documentation at lists.esipfed.org>> wrote:
>
>> Hi, folks,
>>
>>      I’m struggling with how to capture platform and instrument 
>> information in the appropriate places in netCDF files.  The NODC 
>> templates suggest creating separate variables for platforms and 
>> instruments, with multiple variable attributes (make, model, serial 
>> number, precision, accuracy, etc.), and associating these platform 
>> and instrument variables with physical variables via an 
>> “ancillary_variable” variable attribute attached to the physical 
>> variable. Along these lines, SeaDataNet suggests including variable 
>> attributes for instrument (sdn_instrument_urn and 
>> sdn_instrument_name), and OceanSites suggests either the use of a 
>> separate instrument variable (with make, model, serial number 
>> attributes) or capturing make, model and serial number as variable 
>> attributes contained directly within the relevant physical variable.  
>> But ACDD-1.3 only has single /global/ attributes for platform and 
>> instrument (and vocabularies).  The NODC templates suggest placing 
>> the names of the variables containing information on platforms and 
>> instruments in the global attributes: instrument and platform.  I 
>> like NODC’s and OceanSites’ “associative” approach (i.e. “this 
>> instrument goes with this physical variable”), but the use of 
>> variable names in global attributes conflicts with ACDD-1.3.
>>
>>      It seems that in order to comply with ACDD-1.3, I need to 
>> capture instruments and platforms at a global level (dropping their 
>> association with physical measurement variables), but in order to 
>> comply with OceanSites and others, I need to capture instrument and 
>> platform information in separate variables and associate these with 
>> physical measurement variables via an ancillary_variable attribute.
>>
>>      In order to comply with both, in the interest of enabling 
>> interoperability, I seem to need to repeat instrument and platform 
>> metadata in two different places.
>>
>>      Any thoughts or guidance?
>>
>> References:
>> NODC netCDF timeseries template: 
>> http://www.nodc.noaa.gov/data/formats/netcdf/v1.1/timeSeriesOrthogonal.cdl
>> OceanSITES Data Format Reference Manual (See Appendix 2 for sensor 
>> variables): 
>> http://www.oceansites.org/docs/oceansites_data_format_reference_manual.pdf
>> SeaDataNet Data Transports Manual (See Section 4.2.2 Co-ordinate 
>> Variables): 
>> http://www.seadatanet.org/content/download/16251/106283/file/SDN2_D85_WP8_Datafile_formats.pdf
>>
>> Thanks,
>> Aaron
>>
>> -- 
>> Aaron D. Sweeney
>> Water Level Data Manager
>>
>> Cooperative Institute for Research in Environmental Sciences (CIRES)
>> University of Colorado at Boulder
>> and
>> NOAA National Geophysical Data Center
>> Marine Geology and Geophysics Division
>> 325 Broadway, E/GC3
>> Boulder, CO 80305-3328
>>
>> Phone: 303-497-4797, Fax: 303-497-6513
>>
>> DISCLAIMER: The contents of this message are mine personally and do not necessarily reflect any position of NOAA.
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>

-- 
Aaron D. Sweeney
Water Level Data Manager

Cooperative Institute for Research in Environmental Sciences (CIRES)
University of Colorado at Boulder
and
NOAA National Geophysical Data Center
Marine Geology and Geophysics Division
325 Broadway, E/GC3
Boulder, CO 80305-3328

Phone: 303-497-4797, Fax: 303-497-6513

DISCLAIMER: The contents of this message are mine personally and do not necessarily reflect any position of NOAA.

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