945 
fluences internal drainage, surface runoff, and espe 
cially erosion. It also affects the use of farm machi 
nery by inhibiting its use in areas of high relief. 
Information on relief or slope gradient can be very u- 
seful in determining the construction of septic sys 
tems. The extent of each of the dominant relief clas 
ses in Indiana is shown in Table 3. Figure 7 illus 
trates the spatial location of the dominant relief 
classes. This information shows a good relationship 
with potential erosion estimates. 
Table 4 presents all the soil associations in the 
state with their respective tabular information (at 
tributes) used to generate the interpretive maps and 
statistical information. The production of digital 
interpretive maps does not involve changes in the ori 
ginal data set. It uses attribute files to regroup 
the original map units into interpretive classes in 
real time. These new data (Interpretive maps) can be 
used in analysis and modeling processes with other 
resources data sets available in the GIS. 
The element soils constitute one of the basic and 
fundamental component of any natural resources geogra 
phic information system. This is shown by the way in 
which soils are related to other environmental resour 
ces. These relationships indicate potential interac 
tions and provide information which could improve plan 
ning and decision making activities at different levels 
of detail. 
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