Jon Blower wrote:
Dear Jonathan,
Yes, I take your point. Another option would be to allow a simple
attribute on a time axis "nominal_precision" or something similar, which
could take values like "1 day", "1 month" etc. This could be in
addition to the bounds and cell_methods attributes.
The problem with
using the bounds/cell_methods approach in isolation is that it requires
a client to look at the bounds for every point along the time axis to
verify that the bounds for each point is the same length.
Hi Jon,
This comment applies equally to spatial axes; as-is a CF client
application must examine the full coordinate axis and its bounds in
order to determine if an axis is regularly spaced whether time or
space. And yes, this is a particularly acute problem for time axes,
where it is not uncommon to have many thousands of points in a CF
dataset.
There have been discussions in the past of the merits of a
"point_spacing" attribute:
my_axis:point_spacing = "even";
I'd be totally supportive of adding this attribute to CF, myself. It
offers significant efficiencies to clients and it addresses your
question reasonably well (to quickly infer a nominal spacing from the
axis coordinates or its bounds).
- Steve
Best wishes,
Jon
-----Original Message-----
From: Jonathan Gregory [mailto:[email protected]] On Behalf Of
Jonathan Gregory
Sent: 02 June 2010 19:13
To: Jon Blower
Cc: [email protected]
Subject: Re: [CF-metadata] bounds/precision for time axis
Dear Jon
If we decide to let cell_methods indicate "vagueness" I don't think it's
a
problem if the bounds themselves are precise. The precision is somewhat
irrelevant, as you say, but it shouldn't be misleading in view of the
cell_methods. Changing cell_methods is a small alteration to the CF
standard,
whereas introducing alternative ways of representing time is a large and
complex change, which would require substantial alteration to software
as well.
Best wishes
Jonathan
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