[CF-metadata] How to define time coordinate in GPS?

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 13 Jul 2015 17:45:10 +0100

Dear Jim

> If the input times were GPS times, would you - as a modeler
> - feel the need to convert those times to UTC times before using
> them in your model?

No.

> I've never dealt with weather or climate models, but it seems to me
> that while models are precise regarding time, they may not be
> accurate - in that having your inputs off by 15 seconds won't make a
> material difference in your outputs.

That is quite true. In that sense it is inaccurate, like the gregorian case.
However, unlike the gregorian case, it is precise once the data is transplanted
to the model world. In the output, I wish to encode a time coordinate of
exactly midnight on 2015-7-13, for instance, and I want my calendar attribute
to describe this as being in the no-leap-second world, precisely. This means
the data-user will decode my time coordinate precisely correctly. It would
be surprising or confusing if the data-user decoded with leap seconds, getting
a timestamp a quarter of a minute wrong, and "gregorian" would permit that
option. Also, the user can depend on every day having 86400 seconds, if the
coords are used as elapsed times.

Best wishes

Jonathan
Received on Mon Jul 13 2015 - 10:45:10 BST