Dear Jonathan,
thank you again for your responses. We would like to comment on
"surface_reflectance" vs. "surface_albedo", modify our proposal for
"land_cover", and we need some more time to think about
"probability_of_..." and may drop this from the proposal for now.
Am 2012-03-28 10:17, schrieb Jonathan Gregory:
[...]
standard name: surface_reflectance
definition: fraction of incident
radiation<http://en.wikipedia.org/wiki/Reflection_%28physics%29>
reflected by a surface, wavelength dependent
Is this different from surface_albedo, which we already have? surface_albedo
could have a coordinate of radiation_wavelength to make it spectral.
Our expert says that it is different and that it requires another name.
We do not think that anyone would expect the surface reflectance value
in a variable with name surface_albedo with a wavelength attribute. The
surface reflectance is the bidirectional reflectance derived from the
bidirectional reflectance distribution function (BRDF) that defines how
light is reflected at an opaque surface. Surface reflectance is
normalised: the surface reflectance is derived for a given standardised
view observation geometry. Compared to this surface albedo is the
integral of the BRDF over all viewing and illumination directions of a
hemisphere.
So our proposal for "surface_reflectance" remains:
Am 2012-01-31 15:23, schrieb Martin Boettcher:
standard name: surface_reflectance
definition: fraction of incident radiation reflected by a surface,
wavelength dependent
unit: none
attribute: wavelength [unit nm]
example:
float sr_2_mean(time, lat, lon) ;
sr_2_mean:long_name = "normalised surface reflectance of channel 2" ;
sr_2_mean:standard_name = "surface_reflectance" ;
sr_2_mean:wavelength = 442.5 ;
sr_2_mean:valid_min = 0 ;
sr_2_mean:valid_max = 1 ;
sr_2_mean:_FillValue = -999.f ;
Am 2012-03-28 10:17, schrieb Jonathan Gregory:
For the existing standard name land_cover which is a synonym of
area_type we propose to allow for external vocabularies as valids.
Yes, use of external vocabularies is fine if they are standardised, available
online and well-maintained. However, as you say, CF maintains its own area_type
table. Therefore would it be better to introduce a new standard_name
specifically for land cover types of the UN Land Cover Classification System?
I presume that system has some governance arrangement of its own. If we had
a different standard name for it we would avoid conflicts and overlaps.
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 ;
As an alternative, this may be generalised to land_cover_class with the
vocabulary attribute to specify the type of classification defined by
some external standard.
Best wishes
Martin
--
Dr. Martin Boettcher
Brockmann Consult GmbH
Max-Planck-Straße 2
D-21502 Geesthacht
Tel: +49 (0)4152 889 315
Fax: +49 (0)4152 889 333
www.brockmann-consult.de
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Geschäftsführer Dr. Carsten Brockmann
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