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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