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#100: Clarifications to the preamble of section 5
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Reporter: jonathan | Owner: cf-conventi...@lists.llnl.gov
Type: defect | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Keywords: |
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Dear all
I have the honour of opening ticket number 100. In this ticket, Steve
Hankin and I have a number of changes to propose to the text of section 5,
with the intention of clarifying it, not changing what it means. Therefore
this is a defect ticket, but please object if you think it is changing the
meaning, or making it any less clear!
Cheers
Jonathan
Replace this text in the first paragraph
A variable's spatiotemporal dimensions are used to locate data values in
time and space. This is accomplished by associating these dimensions with
the relevant set of latitude, longitude, vertical, and time coordinates.
with
A data variable's dimensions are used to locate data values in time and
space or as a function of other independent variables. This is
accomplished by associating these dimensions with the relevant set of
latitude, longitude, vertical, time and any non-spatiotemporal
coordinates.
These changes clarify that coordinate systems belong to data variables
(rather than any other type of variable in a CF-netCDF file) and recognise
the use of non-spatiotemporal dimensions.
Replace this text in the second paragraph
All of a variable's dimensions that are latitude, longitude, vertical,
or time dimensions (see Section 1.2, "Terminology") must have
corresponding coordinate variables, i.e., one-dimensional variables with
the same name as the dimension
with
Any of a variable's dimensions that is an independently varying
latitude, longitude, vertical, or time dimension (see Section 1.2,
"Terminology") and that has a size greater than one must have a
corresponding coordinate variable, i.e., a one-dimensional variable with
the same name as the dimension
These changes remove the implication that spatiotemporal scalar
coordinates might be prohibited, and allow for discrete axes (section 4.5,
used extensively in section 9).
Replace this text in the third paragraph
All of a variable's spatiotemporal dimensions that are not latitude,
longitude, vertical, or time dimensions are required to be associated with
the relevant latitude, longitude, vertical, or time coordinates via the
new coordinates attribute of the variable
with
Any longitude, latitude, vertical or time coordinate which depends on
more than one spatiotemporal dimension must be identified by the
`coordinates` attribute of the data variable.
This change is for clarity.
Replace this text in the fifth paragraph
The use of coordinate variables is required whenever they are
applicable. That is, auxiliary coordinate variables may not be used as the
only way to identify latitude and longitude coordinates that could be
identified using coordinate variables.
with
If the longitude, latitude, vertical or time coordinate is multi-valued
and varies in only one dimension, it is not permitted to store it as an
auxiliary coordinate variable.
This change is for simplicity and clarity. The use of coordinate variables
where applicable is already required by the second paragraph.
Append to the fifth paragraph
If the longitude, latitude, vertical or time coordinate is single-
valued, it may be stored either as a coordinate variable with a dimension
of size one, or as a scalar coordinate variable (Section 5.7).
This change recognises the use of spatiotemporal scalar coordinates.
--
Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/100>
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