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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