In theory, should be zero for most soil types, but it
changes from -0.1 to 0.2[11,12] because of the influences of
many factors. should be the maximum of ,
but it will change with the spatial or temporal change because
of the influences of vegetation types. Thus, and
can not be fixed values [13] even in the same image.
Vegetation type changes with the change of the land use type.
To the same land use type, vegetation types are same
approximately [14], so the pixels’ are close to the
same vegetation type; the pixels’ are close to the
same soil type too. Thus, the land use map and the soil map
may be used to compute and .