except for your recurring reminder to say "no", unless absolutely
necessary, your proposal has some appeal. There may, however, be more
than one "mask" of interest for a given field, and lots of folks will
object to having to include even one mask in the same file as the
variable it is used to mask. [When lots of fields are stored in
separate files, each one would also have to have the data mask stored
with it.]
regards,
Karl
On 1/3/11 12:34 PM, Steve Hankin wrote:
Trial balloon:
This conversation circles around the idea of masks that serve a
discipline-specific purpose: a land mask for terrestrial types; or a
sea mask for ocean types. Each discipline finds it natural to have
"1" indicate valid points for his particular outlook. It will always
be an effort for the data providers in one discipline to adopt the
conventions of another.
One could imagine masks for other (less common) purposes as well in
which the 1's signify other things. For example there are valid uses
for time masking, in which the 1's would indicate valid time indices.
Perhaps the fact that this conversation is occurring illustrates that
we should be approaching masking in a discipline-neutral way --
defining a new attribute, and a more generic new standard_name.
Something like:
netcdf mask_eg {
dimensions:
AX003 = 10 ;
AX002 = 20 ;
variables:
float LON_U(AX002, AX003) ;
LON_U:long_name = "curvilinear longitudes" ;
LON_U:units = "degrees_north" ;
float LAT_U(AX002, AX003) ;
LAT_U:long_name = "curvilinear latitudes" ;
LAT_U:units = "degrees_east" ;
float U(AX002, AX003) ;
U:coordinates = "LAT_U LON_U" ;
U:_FillValue = -1.e+34f ;
U:long_name = "Zonal Velocity" ;
U:units = "meters/sec" ;
* U:binary_mask = "U_MASK";*
float U_MASK(AX002, AX003) ;
U_MASK:coordinates = "LAT_U LON_U" ;
*U_MASK:standard_name = "binary_mask" ; // "1" indicates valid*
U_MASK:long_name = "Ocean mask" ;
// global attributes:
:Conventions = "CF-1.5" ;
}
Is this a preferable approach?
- Steve
===========================
On 1/3/2011 11:35 AM, Rich Signell wrote:
Chris,
On Mon, Jan 3, 2011 at 12:57 PM, Christopher Barker
<[email protected]> wrote:
On 1/2/11 6:11 PM, Rich Signell wrote:
But they are not the same thing. They are the inverse.
yes, of course, but they carry exactly the same information, do they not.
Yes, one could be inferred from the other.
Why have two ways to express the same information?
Yes, it would
be possible to have data sets providers create NcML for every ROMS
dataset that has ever been written and serve the data with a
land_binary_mask instead of a sea_binary_mask.
well, I suppose it may be a question of whether there are more data
providers or data consumers...
Since most consumers use some kind of tool, I would says it's more a
question of whether there are more data providers or more CF-compliant
tool developers. And since many tool developers use NetCDF-Java or
some other package to enable CF compliance, perhaps there are really
not so many software changes to be made.
That also implies that there are a bunch of ROMS-output netcdf files that
already have a sea_binary_mask variable, and are therefor not currently
CF-compliant. Is that the case? Do we want to add things to the standard to
make common, but not compliant, use cases compliant? Perhaps so.
I think "Perhaps so" is exactly right. The advantage of making it
easier for providers to standardize their datasets vs the additional
burden to CF-compliant tool developers.
-Rich
On Sun, Jan 2, 2011 at 12:31 PM, Chris Barker<[email protected]>
wrote:
On 12/30/2010 2:40 PM, Rich Signell wrote:
CF Standard Name Team:
I would like to request a new standard_name="sea_binary_mask" defined as
sea_binary_mask X_binary_mask has 1 where condition X is met, 0
elsewhere. 1 = sea, 0 = land.
This is used by the popular ROMS ocean model, and perhaps others.
The new "sea_binary_mask" would join the existing "land_binary_mask",
which has 1 = land, 0 = sea.
which makes it completely redundant. How hard it is to translate a
sea_binary_mask into a land_binary mask?
as an end user, now all my code has to look for both, despite them being
the
same thing.
Isn't it an ideal to have only one standard way to express a given
quantity?
-Chris
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
[email protected]
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