By convention, McIDAS datasets all use degrees_west for their longitude
values. I think that the netCDF-Java should support this (just like it
supports "CF" files without the required lat/lon coordinates when there
is a addition to the grid_mapping). I also think it's reasonable for
CF to support this since it is a valid udunit for longitude.
Don
Joe Sirott wrote:
Hi John,
There are a lot of legacy oceanographic in-situ datasets out there that
use the EPIC netCDF convention
<http://www.epic.noaa.gov/epic/document/convention.htm> which in turn
recommends use of "degree_west" (note the missing "s") for the
longitude units attribute.I've found that you need support the 8
combinations (degree_west, degrees_west, ...) of lat/lon unit attributes
in order to reliably handle these kind of datasets. In practice, EPIC
datasets are even more complicated as there is an "epic_code" attribute
that independently specifies the units for the variable. Some datasets
only have the epic_code attribute, some have both, and some (as yet
another proof of Murphy's Law) have an epic_code attribute that
conflicts with the units attribute.
It would be great (at least for me!) if netCDF-java supported all of
these attributes. However, I don't think they should be added to CF, as
this would make CF even more complicated than it already is and I think
that most data providers should be encouraged to use the
degrees_east/degrees_north convention.
- Joe
John Caron wrote:
Tom Whittaker wrote:
We have some point data that has positive-west longitude values. It
appears that netcdf-java (and perhaps the CF conventions) do not
support a unit of "degrees_west". This seems inconsistent, since
degrees_east is supported. While I assume we can work arround this by
adding a scale_factor attribute with a -1.0 value, I would encourage
you to consider this as a valid unit. (I also wonder if
"degrees_south" are recognized? I did not check this.....)
Thanks.....
Hi Tom:
CF does not recognize degrees_west (nor degrees_south). You could
propose adding that to CF, which would be the best easy to solve it
from our POV.
One thing that complicates it is that degrees_north, degrees_east
units is the way to recognize lat/lon coordinates. so now
degrees_west, degees_south would also be.
Can you give me some background on what datasets are likely to be
using these units?
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