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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Received on Wed Apr 18 2018 - 21:39:36 BST
