Dear Ethan
Thanks for taking this up. I think this approach is sensible.
> Perhaps we should include information on when the deprecated feature was in
> effect:
>
> The initial definition for this projection was agreed on in May 2012 though
> it was not in the CF document until 1.7 was released in Sept 2017. It was
> corrected in ??? 2018.
>
> And do we also want to include information about large datasets that use
> this deprecated technique:
>
> In that time, several satellite missions were developed and launched that
> generate data that use this now deprecated method including GOES-R
> (operational in Dec 2017), EUMETSAT ???? ...
Yes, I think it's a good idea to say these things. It's in line with the rules
(never before used!) about what to do if a mistake is discovered. It would also
be appropriate to release 1.8 as soon as we have agreed the change on a trac
ticket, with just this ticket included relative to 1.7, so that the corrected
version is available for use as soon as possible.
Best wishes
Jonathan
----- Forwarded message from Ethan Davis <edavis at ucar.edu> -----
> Date: Wed, 18 Apr 2018 21:39:36 -0600
> From: Ethan Davis <edavis at ucar.edu>
> To: CF metadata <cf-metadata at cgd.ucar.edu>
> Subject: [CF-metadata] Fix Geostationary projection, including proposal for
> two new standard names
>
> Hi all,
>
> Here's an initial proposal for fixing the geostationary projection as we've
> been discussing.
>
> Two new standard names:
>
> *Name:* projection_x_angular_coordinate
> *Canonical units:* radian
> *Definition:* "x" indicates a vector component along the grid x-axis, when
> this is not true longitude, positive with increasing x. Angular projection
> coordinates are angular distances in the x- and y-directions on a plane
> onto which the surface of the Earth has been projected according to a map
> projection. The relationship between the angular projection coordinates and
> latitude and longitude is described by the grid_mapping.
>
> *Name:* projection_y_angular_coordinate
> *Canonical units:* radian
> *Definition:* "y" indicates a vector component along the grid y-axis, when
> this is not true latitude, positive with increasing y. Angular projection
> coordinates are angular distances in the x- and y-directions on a plane
> onto which the surface of the Earth has been projected according to a map
> projection. The relationship between the angular projection coordinates and
> latitude and longitude is described by the grid_mapping.
>
>
> Replace the text of the current "Map coordinates:" section with
>
> The x (abscissa) and y (ordinate) projection coordinates are identified by
> the `standard_name` attribute values `projection_x_angular_coordinate` and
> `projection_y_angular_coordinate` respectively. In the case of this
> projection, the projection coordinates are directly related to the scanning
> angle of the satellite instrument.
>
>
> Add a deprecation note below the current "Notes:"
>
> *Deprecation Note:*
> The use of `projection_x_coordinate` and `projection_y_coordinate` for this
> projection has been deprecated.
>
> The initial definition of this projection used these standard names to
> identify the projection coordinates even though their canonical units
> (meters) do not mach those required for this projection (radians).
>
>
> Perhaps we should include information on when the deprecated feature was in
> effect:
>
> The initial definition for this projection was agreed on in May 2012 though
> it was not in the CF document until 1.7 was released in Sept 2017. It was
> corrected in ??? 2018.
>
>
> And do we also want to include information about large datasets that use
> this deprecated technique:
>
> In that time, several satellite missions were developed and launched that
> generate data that use this now deprecated method including GOES-R
> (operational in Dec 2017), EUMETSAT ???? ...
>
>
> That could alert people to the likelihood they (or any software they
> develop) might run into data using this deprecated feature.
>
> I'll move this to a Trac ticket (with an accompanying GitHub PR) once we
> discuss a bit.
>
> Cheers,
>
> Ethan
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> CF-metadata at cgd.ucar.edu
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----- End forwarded message -----
Received on Thu Apr 19 2018 - 09:22:23 BST
