classification attempts to actually determine land use and 
not just land cover it naturally defines agricultural land 
more broadly than would be possible from satellite imagery. 
Consequently the USGS file has fewer areas that are left 
in the category of barren land. Nevertheless, the two 
files reveal good correspondence both in terms of magnitude 
and spatial alignment of agricultural land. 
Forests, the major use of land in South Carolina, are 
difficult to classify into relevant subcategories utilizing 
remote sensing procedures. In order to compare the two 
processes in this study, electrostatic plots were generated 
for cells classified as mixed, deciduous or evergreen 
forests. The two plots for each category were then photo 
graphically overlaid to display areas of agreement (Figs. 
4-6). This process clearly reveals some major differences 
in the two categorizing procedures and dramatically 
indicates a need for a more systematic method for classifi 
cation of forests from remotely sensed data. 
According to the USGS classification, an area of mixed 
forest must include a one-third intermixture of either 
evergreen or deciduous trees, as well as have an overall 
density of at least ten per cent (Anderson et al, 1976 p. 
16). General agreement between the areas of mixed forest 
can be found both in the northwestern portion and central 
coastal sections of the State (Fig. 4). In other areas it 
appears that the mixed category has been employed too 
frequently. This probably is attributable to a combination 
of insufficient ground truth information and a general 
tendency to merge several spectral classes into this rather 
nebulous category. 
The most startling differences between the two classifi 
cations are related to the categories of deciduous and 
evergreen forests (Figs. 5 and 6). The most striking aspect 
is the straight lines on the USGS plots for both deciduous 
and evergreen forests. These lines correspond directly to 
the map sheet boundaries and are particularly noticeable 
between the Florence and Georgetown quadrangles (Fig. 2). 
Obviously there was either something different in the raw 
materials used for the classification or in the interpre 
tation of the photography. Since the coastal map sheets 
were compiled during the same time period, it is more 
likely that the differences relate to the interpretation 
process than to the imagery. 
In addition to the interpretation problem with the USGS 
maps, there is also a problem of inadequate spatial 
correspondence with the Landsat derived map for both 
deciduous and evergreen forests. A particular concern 
relates to the classification of bottomland hardwoods that 
are found along the major river systems. While they are 
prominant features of the Landsat derived map of deciduous 
forests, they are noticeably absent from the same USGS map. 
Subsequent analysis revealed that most of the floodplains 
for the coastal quadrangles had been classified as forested 
wetlands by the USGS. Generally, the USGS has made a 
purposeful attempt to delineate forested wetlands whenever 
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