Thanks, Jim, I will take it to ACDD.
Mary Jo
On Tue, 16 Aug 2016, Jim Biard wrote:
Date: Tue, 16 Aug 2016 12:43:57 -0400
From: Jim Biard <[email protected]>
To: [email protected]
Subject: Re: [CF-metadata] Best practice to include spatial resolution for
projected data
Mary Jo,
It's a problem that doesn't currently have an official solution. The
geospatial_lat/lon_resolution are from the ESIP Attribute Convention for
Dataset Discovery (ACDD) <http://wiki.esipfed.org/index.php/ACDD>, but they
haven't thought through to a generalization yet. You could make your own
attributes geospatial_resolution or geospatial_x_resolution and
geospatial_y_resolution, or you could think of longitude as being ~x and
latitude as ~y and use the existing attributes. You can also query the ESIP
people and request that they add a new set of attributes that would handle
this. I think the CF community likely considers this to be more of an ACDD
issue.
Grace and peace,
Jim
On 8/16/16 12:33 PM, Mary Jo Brodzik wrote:
I am producing a gridded data set using CF-1.6 conventions. In a given
file, the data are projected onto one of three possible projections:
Northern or Southern Lambert Azimuthal Equal Area (LAEA), or Cylindrical
Equal-Area (CEA). With each data variable in the file, I do include the
grid_mapping attribute and I am populating my grid_mapping variable with
the required projection information as listed here:
http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html
Also in a given file, the spatial resolution will be one of 25, 12.5, 6.25
or 3.125 km, and although this is obvious from the x and y dimension
variable values, I am looking for a place to include the spatial resolution
for a human who is reading the metadata.
I assume an attribute in the grid_mapping variable would be the place for
this. At first I thought it was one of the "scale_factor*" attributes,
e.g. "scale_factor_at_projection_origin", but for CEA, this would be a
misnomer, since the value is the scale at true latitude, not the projection
origin at all. Also, the convention says to include "either
standard_parallel or scale_factor_at_projection_origin", so now I'm
beginning to think these "scale_factor_*" attributes are not the correct
place at all for this information.
I see in the NCEI template file for gridded data
https://www.nodc.noaa.gov/data/formats/netcdf/v2.0/grid.cdl
that they recommend global attributes like "geospatial_lat_resolution" and
"geospatial_lon_resolution", with a string value of "0.1 degree" or "100
meters" which is almost what I am looking for, but of course since I have
projected data it would not be "lat" or "lon".
Can anyone recommend a best practice for my projected data case that I can
follow?
Thank you,
Mary Jo Brodzik
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Mary Jo Brodzik, Senior Associate Scientist, 303-492-8263
NSIDC/CIRES, Univ. of Colo. at Boulder, 449 UCB, Boulder, CO 80309-0449
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Mary Jo Brodzik, Senior Associate Scientist, 303-492-8263
NSIDC/CIRES, Univ. of Colo. at Boulder, 449 UCB, Boulder, CO 80309-0449
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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