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
> <Chris.Barker at noaa.gov> 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<Chris.Barker at noaa.gov>
>>> 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
>>
>> Chris.Barker at noaa.gov
>>
>
>
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