Use of the DSMW
For the countries in categories 4 and 5 (see Table 2-1), the DSMW was used. The following steps were applied:
- importing the data available in the ArcInfo® export format into ArcInfo®. They are in geographical
co-ordinates (not projected). The data was divided into three different categories:
- afscntll: for Africa
- euscntll: for Europe
- nescntll: for Asia
- eliminating the countries situated outside the area of interest;
- harmonising the structure of the three categories for having the same naming and structure
for all the attributes;
- projecting the categories into the projection used for the SGDBE;
- harmonising the structure of the categories to be compatible with the structure of the
SGDBE;
- realising a geometrical fitting following the procedure elaborated for the SGDBE, and using
data from the Digital Chart of the World on the basis of:
- country borders,
- river patterns compared to the extent of Fluvisols,
- lakes,
- temporary hydrological patterns compared with saline soils for Northern African countries,
- applying geometrical conformity rules to the fitted categories;
- adding the fitted categories to that of the SGDBE following the procedure elaborated for the SGDBE.
For the semantic data, i.e. the description of soil associations, they are available in one file named worldexp.dat, in ASCII format. The structure of the file is described in Table 2-2.
The data was imported into ArcInfo® as an INFO file. Then, the structure was changed to have two separate files for the SGDBE:
- one file giving the organisation of soil types within SMU,
- the other giving the description of the soil types with the same structure as those of the SGDBE:
- the attributes FAO85-FULL, TEXT-SRF-DOM, TEXT-SRF-SEC, SLOPE-DOM, SLOPE-SEC, AGLIM1 and AGLIM2 are entered
- the other attributes have no information.
The minimum value of the texture class was given to the dominant texture class. The same approach was used to determine the dominant slope class (Table 2-3 and Table 2-4). That means if the texture classes are 1 and 2, then the dominant texture class is 1 (the minimum value) and the secondary texture class is 2. It is not the minimum value in the sense of percentage of area. Both classes have the same percentage of area in the DSMW file. An adaptation of the coding used within the SGDBE was necessary because in the DSMW, texture and slope are only in 3 classes (Table 2-5 and Table 2-6).
The values for the phases where copied from those of the soil association to all the STUs that are within the soil association. An adaptation of the codes was made to maintain the particularity of the DSMW codes (Table 2-7). For some countries, parent material information was available in the booklets of the Soil Map of the World. This information has been added to the STU description using the codes for the attributes of the SGDBE MAT1 and MAT2, and PARMAT- DOM and PAR-MAT-SEC.
Only soil associations and soil types from the area of interest were kept and the two files obtained were added to those of the SGDBE.
Table 2-3: Correspondence for texture class values between the DSMW and the SGDBE
Table 2-4: Correspondence for slope class values between the DSMW and the SGDBE
Table 2-5: Definition of texture classes
Table 2-6: Definition of slope classes
Table 2-7: Definition of the agricultural limiting constraints classes