[Esip-documentation] on documenting instrument and platform metadata

[Aaron Sweeney]

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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