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The Generic IWMI 951 Class map
(Generic-IWMI-951)
is the base product from which the Global irrigated area
map (GIAM), the Global Map of Rainfed Cropland Areas (GMRCA),
and Global Map of Land Use/Land Cover Areas (GMLULCA) were
derived. The methodology on how the 951 class map was produced
has been presented in the detailed documentation presented in this
paper. First, the irrigated area classes, the rainfed area
classes, and the other land use/land cover (LULC) classes were
identified and labeled based on an elaborate set of methods
and techniques (see documentation) for each of the
seven segments of the World. The seven segments were:
1.
Precipitation less than 360 mm per year segment
(PLT360-segment);
2.
Precipitation greater than 2400 mm per year segment
(PGT2400-segment);
3.
Temperature less than 280 degree Kelvin segment
(TLT280-segment);
4.
Forest cover greater than 75 mm segment
(FGT75-segment);
5.
Elevation greater than 1500 mm segment
(EGT1500-segment);
6.
All other areas of the World segment (AOAW-segment);
and
7.
Rainforest synthetic aperture radar segment
(RFSAR-segment).
The segments were
masked and analyzed using the time-series mega-file data from
SPOT 1-km, AVHRR 10-km, and secondary datasets such as
1-kmGTOPO30 elevation, 1-km forest cover, 40-yr monthly
rainfall, and 10-km AVHRR skin temperature. The classes
identified from each of the segments were mosaicked into a
single file that added up to 951
classes and is called Generic IWMI 951 Class Map (Generic-IWMI-951). The 951 classes were
refined into various aggregated and disaggregated maps
specifically for GIAM, GMRCA, and GMLULCA.
The Generic 951
class map and image are specifically useful for
those interested in producing their own refined map. For
example, a more detailed irrigated area map or rainfed
cropland map, or a LULC map of specific Countries or regions
will be of value when the can better combine and/or label
classes based on local knowledge. It must be noted that the
class labels in the 951 class map/image are indicative rather
than definitive. So a user can always label a class better.
The characteristics include, for each of
the 951 classes: (a) month-by-month 10-km AVHRR spectral band
reflectivity for band 1 (red) and band 2 (near-infrared), (b)
month-by-month 10-km AVHRR brightness temperature for thermal
bands 4 and 5; (c) month-by-month 10-km AVHRR NDVI, (d)
month-by-month 1-km SPOT vegetation NDVI, (e) elevation
(meters), (f) skin temperature (degree kelvin), (g) mean
rainfall (mm/month), and (h) tree cover
(percent).
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