Currently, a coordinate variable that makes use of the standard NetCDF scaled integer convention is not CF metadata compliant.

In addition to the reduction in NetCDF dataset (file) size, there are other advantaged to allowing it including simplifying product formatting software, and having an attribute (scale_factor) that provides insight into the spatial resolution of the data variable.

To update the CF metadata conventions standard document requires changing a two rows in Table A.1 Attributes in Appendix A.

(1) In the "add_offset" row, the "Use" column needs to change from "D" to "C, D"

(2) In the "scale_factor" row, the "Use" column needs to change from "D" to "C, D"

Appendix A, Attributes, indicates that the 'comment' attribute may be used as a global attribute or for non-coordinate data variables. Its description states that it is for 'Miscellaneous information about the data or methods used to produce it.'

For in situ ocean data, certain information about the coordinate variables seems to belong in a comment; coordinate values have characteristics that should be described, but there are no standards for these descriptions yet.

For example, for a surface mooring, this seems like the best place to indicate whether the latitude and longitude are the surveyed anchor position or a GPS fix from the buoy itself, and whether the depth is the combined length of line/chain/instrument cases between the surface and the sensor, or a calculated depth based on measured pressure.

So, I propose that in the table in Appendix A we change the 'Use' of the comment attribute from G,D to G,C,D, to allow comments for variables containing coordinate data.

-Nan

Objective

The purpose of this ticket is to agree the scope and terms of reference for the CF data model.

Proposal

Scope, Terms and Conditions

1. The CF community will adopt a data model as part of the CF Metadata Project.
2. The data model will be a complementary resource to the:
   • CF Conventions Document
   • CF Standard Name Table
   • CF Conformance Requirements & Recommendations
   • Guidelines for Construction of CF Standard Names
3. The data model will be maintained by the community, using the same mechanisms as are used for the conventions, conformance and standard_name documents.
   • ​http://cf-pcmdi.llnl.gov/governance/governance-rules
   • ​http://cf-pcmdi.llnl.gov/governance/governance-rules-correcting-errors
4. The data model, once it has reached v1.0, will be consistent with the CF Conventions Document.
   • This consistency will be maintained.
     • Changes to the specification should be evaluated to determine whether they are consistent with the data model: if inconsistencies exist, these should be addressed, either by altering the specification change proposal or by proposing a change to the data model.
5. The scope of the data model is to define the concepts of CF and the relationships that exist between these concepts.
6. The data model provides a logical abstraction of the concepts defined by CF, independent of implementation details.
7. The data model does not define the interface to CF.

Benefits

The data model is believed to offer the following benefits providing:

• an orientation guide to the CF Conventions Document
• a guide to the development of software compatible with CF
• a reference point for gap analysis and conflict analysis of the CF specification
• a communication tool for discussing CF concepts and proposals for changes to the CF specification