Thanks for correcting my typo, @snowman2. I agree with Karl @taylor13's second 
point. It is a general statement. However, I think we're introducing 
unnecessary repetition. I appreciate that the modified text is in the pull 
request, but our guidelines are that we should discuss it as far as possible in 
the issue, so there's only one place to look to see the discussion. So I'm 
repeating the whole of paragraph and the previous one for context. I propose 
minor deletions for conciseness and to reduce repetition. How's this:

The crs_wkt attribute is intended to act as a supplement to other 
single-property CF grid mapping attributes (as described in Appendix F); it is 
not intended to replace those attributes. If data producers omit the 
single-property grid mapping attributes in favour of the compound crs_wkt 
attribute, software which cannot interpret crs_wkt will be unable to use the 
grid_mapping information. Therefore the CRS should be described as thoroughly 
as possible with the single-property attributes as well as by crs_wkt.

In cases where CRS property values can be represented by both a single-property 
grid mapping attribute and the crs_wkt attribute, the grid mapping should be 
provided, and if both are provided, the onus is on data producers to ensure 
that their property values are consistent. Therefore information from either 
one (or both) may be read in by the user without needing to check both. 
However, if the two values of a given property are different, the CRS 
information cannot be interpreted accurately and users should inform the 
provider so the issue can be addressed. For example, if the semi-major axis 
length of the ellipsoid is defined by the grid mapping attribute 
semi_major_axis disagrees with the crs_wkt attribute (via the WKT SPHEROID[…​] 
element), the value of this attribute cannot be interpreted accurately. 
Naturally if the two values are equal then no ambiguity arises.

Jonathan

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