[PI] Quality Flag Handling #3358
Description
Provision of support for "Quality Flags"
Required work
The relevant PRs to implement support for quality flags are below:
- Include support for standard_name modifiers Support Standard Name Modifers (not units!) #3393
- Decide on how to handle units and standard name modifiers Decide what to do about standard name modifiers units #3408
- Include support for Ancillary Variables Include AncillaryVariables and restructure Cube metadata. #3422
- Included loading/saving of Ancillary Variables (outstanding issue Add Support for Loading/Saving Ancillary Variable to/from NetCDF #3473)
- Support for status flags (outstanding issue [PI] Ensure flags are correctly loaded/saved to/from NetCDF #3474)
Description:
Quality flags can be encoded in CF compliant data by using the "ancillary variable" and with "flag" values. This convention allows for a more explicit descriptions of the "quality flags" that one would like to associate with the data. (See snipped below for example)
According to the CF conventions: http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/cf-conventions.html#ancillary-data
However, at present, there are a couple of small issues when creating a "flag" auxiliary coordinate, as the current implementation does allow the issues below to be correctly handled:
- The status_flag standard name should be recognised as so if the cube name is also a standard_name. (At present it come in as a long name.) See Appendix C, Standard Name Modifiers.
- The ancillary_variable should be a local attribute, as it is directly associated the specific data. (i.e. like a latitude coord would be local to the data).
- status_flags should not have units (they are described instead). See Appendix C, Standard Name Modifiers.
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The following code was used to generate the flag coordinate, the meta data for which is shown above:
