Improve CF Conformance: 5 Coordinate Systems and Domain

[jamesdoyle21]

5 Coordinate Systems and Domain
Requirements:

• All of a variable’s dimensions that are latitude, longitude, vertical, or time dimensions must have corresponding coordinate variables.

• A coordinate variable must have values that are strictly monotonic (increasing or decreasing).

• A coordinate variable must not have the _FillValue or missing_value attributes.

• The type of the coordinates attribute is a string whose value is a blank separated list of variable names. All specified variable names must exist in the file.

• The dimensions of each auxiliary coordinate must be a subset of the dimensions of the variable they are attached to, with two exceptions. First, a label variable of type char will have a trailing dimension for the maximum string length. Second, a ragged array (Chapter 9, Discrete sampling geometries and Appendix H) uses special, more indirect, methods to connect the data and coordinates.

[jenseva]

Thanks for your work on the CF checker! It is a very helpful tool that I use often.

I am in the process of writing new files in the unusual format of CF 1.8 with the discrete geometry ragged array of trajectory profiles Appendix H.6.3.

https://cfconventions.org/Data/cf-conventions/cf-conventions-1.8/cf-conventions.html#_ragged_array_representation_of_trajectory_profiles

I get an error from the checker on my test file although as far as I can tell from the CF 1.8 docs it is to spec. Here is a sample error:

§5 Coordinate Systems | dimensions for auxiliary coordinate variable time (profile) are not a subset of dimensions for variable salinity (obs)

Upon finding this issue here, I am hoping this is a known issue with the checker. Can I simply ignore this particular error when it comes to CF 1.8 Ragged array of trajectory profiles (H.6.3)?

[benjwadams]

Sorry for the very late reply. Probably yes. We're going to work through getting the rest of ragged array dimensions working.