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
>> <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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