interspersed with forest vegetation -- evidence of man attempting to
employ every bit of land and slope practical. Owing to a longer history
of settlement and changing economies and technology,the interpreter was
confronted with instances of land abandonment, timber cutting, planned
and unplanned forest regrowth, active and inactive pastures, and idle
land (see Figures 2, 5, 6, and 7). The collage of small, irregular units
in random arrangement severely limited the amount and type of land use
information available. A quite different result was evident in the West
and Midwest. Continuous stretches of rectangular fields characterized the
extensive cultivation practiced in the eastern segments (Figure 1). As
this activity abated grazing and open range land use gained dominance
(Figures 4 and 8). Fields ranged in size from 16 hectares up to 259
hectares and contained crops or improved pastures. Settled much later
than Study Area I this environment is still supplying much of the nation's
and world's agricultural needs and reflected a more ordered settlement
pattern with readily identifiable borders.
The number of detectable settlement pattern features expanded or
contracted as a function of environment. Individual farmsteads were not
visible in Study Area I nor were many small hamlets and villages. Their
presence was masked by the ever present tree canopy except for the larger
urban concentrations. To some degree this invisibility was a result of
the age of settlement and the type and size of farms present in the area.
Farms were devoted primarily to dairying and less equipment, machinery,
and buildings were requisite compared to other farm types. Farmsteads
were also concealed by surrounding forests, woodlots, and topography.
Villages were primarily clusters of residences that may or may not
perform service center functions. Again, trees tended to inundate and
conceal the underlying building structures (Figure 2). Consequently, the
radar return was recorded as a composite of structure and vegetation or
simply as the vegetation canopy. ' Larger urban centers were identifiable
but the lack of a gridded street pattern, the masking effect of trees,
and the noncoterminous urban expansion pattern necessitated extremely
close examination and delimiting the extent of urban build up was generally
tenuous. A quite different experience characterized Study Area II.
Farmsteads were placed periodically on the landscape as were urban
settlements (Figure 1). Although frequently not larger in population
than the Northeast, settlements tended to occupy larger areas, have more
buildings, and perform more service center functions. Vegetation was an
interpretation asset; where man had settled he had planted trees where
none or few existed or left those around his dwellings and removed others
for cultivation. The combination of trees and man-made structures pro-
duced a bright return that contrasted with the surrounding non-forested
areas and enhanced visibility. The ability to more readily discern
gridded street patterns on radar imagery also facilitated settlement
detection.
The overriding factors governing the environmental variation in
visibility of transportation and communication elements were topography
and vegetation. Of lesser importance were orientation with respect to
flightline, polarization, type of transportation, and surface material.
In areas of considerable topographic relief and mature forest stands,such
as central Pennsylvania, not only was most of the transportation network
on the far slopes obscurred as expected, but portions on foreslopes and
orthogonal to the flightline were found to be screened by the forest
canopy (Figure 5). Similar conditions prevailed in Northeast urban areas
where
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