Dear All,
At the start of the year Martin Boettcher proposed a number of new standard names, one of which was for a new land cover quantity that would be used in conjunction with flag_values and flag_meanings attributes. In many ways it would be similar to the existing area_type standard name. The difference between the two names would be that, whereas area_type uses standardised strings from the CF area_type table, the new name would use values taken from an external vocabulary of surface types. The vocabulary in question is the UN Land Cover Classification System (LCCS) which is available online and referenced in the definition of the proposed name. The most recent summary of the proposal (dated 14th May) is reproduced below :
> We agree to introduce a new standard name. Our proposal is
> "land_cover_lccs". The reference to the LCCS standard maintained by FAO
> is http://www.fao.org/DOCREP/003/X0596E/X0596e00.htm .
>
>So, our modified proposal is:
> standard name: land_cover_lccs
> definition: A variable with the standard name of land_cover_lccs
> contains strings which indicate the nature of the surface
> e.g.cropland_..., tree_.... These strings are standardised. Values
> must be combinations of classifiers from the Land Cover Classification
> System (LCCS; Di Gregorio A., 2005, UN Land Cover Classification
> System (LCCS) - Classification concepts and user manual for Software
> version 2; available at http://www.fao.org/DOCREP/003/X0596E/X0596e00.htm)
> unit: none (flag_values and flag_meanings)
> attribute: reference to vocabulary used
> examples:
>
> byte lccs_class(lat, lon) ;
> lccs_class:long_name = "Land cover class defined in LCCS" ;
> lccs_class:standard_name = "land_cover_lccs" ;
> lccs_class:flag_values = 0b, 10b, 20b, 30b, 40b, 50b, 60b, 70b, 80b,
> 90b, 100b, 110b, 120b, 130b, 140b, 150b, 160b, 170b, 180b, 190b, 200b,
> 210b, 220b, 230b, 240b ;
> lccs_class:flag_meanings = "no_data cropland_rainfed
> cropland_irrigated mosaic_cropland mosaic_natural_vegetation
> tree_broadleaved_evergreen_closed_to_open
> tree_broadleaved_deciduous_closed tree_broadleaved_deciduous_open
> tree_needleleaved_evergreen_closed tree_needleleaved_evergreen_open
> tree_needleleaved_deciduous_closed tree_needleleaved_deciduous_open
> tree_mixed mosaic_tree_and_shrub mosaic_herbaceous shrubland grassland
> sparse_vegetation tree_cover_flooded_fresh_or_brakish_water
> tree_cover_flooded_saline_water shrub_or_herbaceous_cover_flooded
> urban bare_areas water snow_and_ice" ;
> lccs_class:vocabulary = "UN-LCCS 2005" ;
> lccs_class:valid_min = 1 ;
> lccs_class:valid_max = 240 ;
> lccs_class:_FillValue = 0b ;
Jonathan Gregory supported the proposal with the modification that the name should be unlccs_land_cover for clarity and Martin agreed to this change; no other comments have been received. Having looked at the reference for the vocabulary in question, it is clear to me that a great deal of work has gone into defining it and it would not be a sensible use of resources for the CF community to duplicate this effort by introducing all the possible land classifications into the area_type table. Therefore, I support this proposal, bearing in mind the point made in the discussion that the CF checker would not be required to check the strings in the flag_values attribute as they can potentially be constructed in more than one order from components of the vocabulary. It would instead be the data provider's responsibility to construct the strings correctly. Unless any objections are received in the next seven days, the proposal for unlccs_land_cover will be accepted for inclusion in the standard name table.
Another new standard name, surface_reflectance (a dimensionless quantity), was also included in Martin's proposal and after discussion was modified to surface_bidirectional_reflectance. This is analogous to the existing name toa_bidirectional_reflectance and would be defined as 'The surface called "surface" means the lower boundary of the atmosphere. "Bidirectional_reflectance" depends on the angles of incident and measured radiation. Reflectance is the ratio of the energy of the reflected to the incident radiation. A coordinate variable of radiation_wavelength or radiation_frequency can be used to specify the wavelength or frequency, respectively, of the radiation.' This proposal seems uncontroversial and the name is accepted for publication in the standard name table.
Martin's original posting,
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2012/055260.html, also included proposals for three new standard names probability_of_fire_occurrence, probability_of_snow_occurrence and probability_of_water_occurrence which would be used with satellite data to indicate whether a pixel was deemed likely to contain each of the surface categories. It was intended that the data variables with these standard names would be used in conjunction with ancillary data variables named using newly proposed standard name modifiers of "confidence_level", "consistency_level" and "source_flag". There was some discussion of these proposals, however, on 14th May Martin wrote:
>
> we need some more time to think about "probability_of_..." and may drop this from the proposal for now.
>
Martin, please could you confirm whether you do in fact wish to withdraw the proposals for the probability names and modifiers from consideration for the time being? If you prefer the proposals to remain under consideration then that is also fine - please just let me know your preferred course of action.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
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Received on Mon Dec 03 2012 - 07:16:23 GMT
