Hello Andrew thank you for the response, my reading of your cases is that they are all 'a' or 'b' in the terms I stated.
There are no ancillary variables which reference a dimension of the netCDF file not referenced by the data variable with the ancillary_variables attribute. I think these are types of case I am particularly concerned to find examples of, or, preferably, discount explicitly. much obliged mark > On 2/13/13 12:15 PM, Hedley, Mark wrote: >> a. reference the same file dimensions as the data variable with the >> ancillary_variables attribute references >> >> b. reference a subset of the file dimensions referenced by the data >> variable with the ancillary_variables attribute >> >> c. reference file dimensions which are not referenced by the data >> variable >> with the ancillary_variables attribute -----Original Message----- From: andrew walsh [mailto:[email protected]] Sent: Fri 2/15/2013 3:20 AM To: Hedley, Mark Cc: [email protected]; [email protected] Subject: Re: [CF-metadata] Ancillary Data Hi Mark, We are using the ancilliary_variables attribute in a real world case for CTD profile data (1 netCDF per CTD profile). Not sure if our use case fits with with your examples a,b,c but here is a abbreviated CDL version:- dimensions: pressure = UNLIMITED ; // (9 currently) variables: double time ; time:standard_name = "time" ; .... byte time_qc_flag; time_qc_flag:long_name = "quality control flag for time (Level 1 flag)" ; .... double latitude ; latitude:standard_name = "latitude" ; ... double longitude ; longitude:standard_name = "longitude" ; ... byte position_qc_flag; position_qc_flag:long_name = "quality control flag for position (Level 1 flag)" ; .... double pressure(pressure) ; pressure:standard_name = "sea_water_pressure" ; ... double temperature(pressure) ; temperature:_FillValue = -99.99 ; temperature:standard_name = "sea_water_temperature" ; temperature:units = "degrees_C" ; temperature:valid_min = -2 ; temperature:valid_max = 40 ; temperature:ancillary_variables = "temperature_whole_profile_flag temperature_qc_flag temperature_sd_test" ; temperature:coordinates = "time latitude longitude pressure" ; byte temperature_whole_profile_flag ; temperature_whole_profile_flag:long_name = "qc flag for whole temperature profile (primary L1 flag)" ; temperature_whole_profile_flag:quality_control_convention = "Proposed IODE qc scheme March 2012" ; temperature_whole_profile_flag:valid_min = 1 ; temperature_whole_profile_flag:valid_max = 9 ; temperature_whole_profile_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; temperature_whole_profile_flag:flag_meanings = "good not_evaluated_or_unknown suspect bad missing" ; byte temperature_qc_flag(pressure) ; temperature_qc_flag:long_name = "quality control flag for temperature (primary Level 1 flag)" ; temperature_qc_flag:standard_name = "sea_water_temperature status_flag" ; temperature_qc_flag:quality_control_convention = "Proposed IODE qc scheme March 2012" ; temperature_qc_flag:valid_min = 1 ; temperature_qc_flag:valid_max = 9 ; temperature_qc_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; temperature_qc_flag:flag_meanings = "good not_evaluated_or_unknown suspect bad missing" ; temperature_qc_flag:coordinates = "time latitude longitude pressure" ; byte temperature_sd_test(pressure) ; temperature_sd_test:long_name = "qc flag for monthly temperature standard deviation test (secondary L2 flag)" temperature_sd_test:quality_control_convention = "Proposed IODE qc scheme March 2012" ; temperature_sd_test:valid_min = 0 ; temperature_sd_test:valid_max = 2 ; temperature_sd_test:flag_values = 0b, 1b, 2b ; temperature_sd_test:flag_meanings = "passed failed unknown" ; temperature_sd_test:coordinates = "time latitude longitude pressure" ; double salinity(pressure) ; salinity:_FillValue = -99.99 ; salinity:standard_name = "sea_water_practical_salinity" ; salinity:units = "psu" ; salinity:valid_min = 0 ; salinity:valid_max = 45 ; salinity:ancillary_variables = "salinity_whole_profile_flag salinity_qc_flag salinity_sd_test" salinity:coordinates = "time latitude longitude pressure" ; byte salinity_whole_profile_flag ; salinity_whole_profile_flag:long_name = "qc flag for whole salinity profile (primary L1 flag)" ; salinity_whole_profile_flag:quality_control_convention = "Proposed IODE qc scheme March 2012" ; salinity_whole_profile_flag:valid_min = 1 ; salinity_whole_profile_flag:valid_max = 9 ; salinity_whole_profile_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; salinity_whole_profile_flag:flag_meanings = "good not_evaluated_or_unknown suspect bad missing" ; byte salinity_qc_flag(pressure) ; salinity_qc_flag:long_name = "quality control flag for salinity (primary Level 1 flag)" ; salinity_qc_flag:standard_name = "sea_water_practical_salinity status_flag" ; salinity_qc_flag:quality_control_convention = "Proposed IODE qc scheme March 2012" ; salinity_qc_flag:valid_min = 1 ; salinity_qc_flag:valid_max = 9 ; salinity_qc_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; salinity_qc_flag:flag_meanings = "good not_evaluated_or_unknown suspect bad missing" ; salinity_qc_flag:coordinates = "time latitude longitude pressure" ; byte salinity_sd_test(pressure) ; salinity_sd_test:long_name = "qc flag for monthly salinity standard deviation test (secondary L2 flag)" salinity_sd_test:quality_control_convention = "Proposed IODE qc scheme March 2012" ; salinity_sd_test:valid_min = 0 ; salinity_sd_test:valid_max = 2 ; salinity_sd_test:flag_values = 0b, 1b, 2b ; salinity_sd_test:flag_meanings = "passed failed unknown" ; salinity_sd_test:coordinates = "time latitude longitude pressure" ; int profile ; //Unique integer to identify each profile profile:long_name = "profile identifier" .... Andrew Walsh ----- Original Message ----- From: "Hedley, Mark" <[email protected]> To: <[email protected]>; <[email protected]> Sent: Thursday, February 14, 2013 10:40 PM Subject: Re: [CF-metadata] Ancillary Data > Hi Nan > > I think I understand you approach, it seems logical and helpful to me. > > It feels like all your examples are in my category b: > >> b. reference a subset of the file dimensions referenced by the data variable >> with the ancillary_variables attribute > > and thus relate to the data variable in the same way auxiliary_coordinates > do, > just with different inferred semantics. > > many thanks for the feedback > > mark > > -----Original Message----- > From: CF-metadata on behalf of Nan Galbraith > Sent: Wed 13/02/2013 19:55 > To: [email protected] > Subject: Re: [CF-metadata] Ancillary Data > > I use a singleton variable to record the magnetic correction that's been > applied to my wind and/or current variables; it's dim(1) and is listed as > an ancillary to any variables that have been affected by the rotation. > > It could be an attribute of each of those variables, but making it a > free-standing > variable lets me give it units and attributes. That's important because I > record the model name and version date, the URL of the NGDC calculator > site, > the inputs to the model (date and location for which the calculation was > done) > and the estimated rate of change. > > Maybe this is just a technicality - but I also use an empty 'container' > variable for > instruments, which has ancillary variables with a depth dimension for > manufacturer, > model, serial number, and reference URL. The instrument variable is > tied to 'obs data' > variables via NODC's 'instrument' attribute, but has no dimensions of > its own; the > individual component variables (like serial number) have a dimension > that matches > the depth dimension of the obs data variables. > > - Nan > > On 2/13/13 12:15 PM, Hedley, Mark wrote: >> Hello CF community >> >> I have been perusing the CF conventions again, particularly the section on >> Ancillary Data >> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch03s04.html >> >> The conventions make the statement: >> >> The nature of the relationship between variables associated via >> ancillary_variables must be determined by other attributes. >> >> The example given provides data variables which reference the same >> dimensions >> in the file: thus they data arrays are the same size. However, the >> conventions do not seem to mandate this. >> >> I am interested in the use of the >> ancillary_variables >> attribute in real world datasets. >> >> Do people have examples they can share of ancillary datasets which: >> >> a. reference the same file dimensions as the data variable with the >> ancillary_variables attribute references >> >> b. reference a subset of the file dimensions referenced by the data >> variable with the ancillary_variables attribute >> >> c. reference file dimensions which are not referenced by the data >> variable >> with the ancillary_variables attribute >> >> I am particularly interested in examples of case c, as I feel this is >> markedly different from cases a and b and requires a different kind of >> support if it is in use. >> >> many thanks >> mark >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> > > > -- > ******************************************************* > * Nan Galbraith Information Systems Specialist * > * Upper Ocean Processes Group Mail Stop 29 * > * Woods Hole Oceanographic Institution * > * Woods Hole, MA 02543 (508) 289-2444 * > ******************************************************* > > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
