The city comprises both a physical system having physical structure 
and a social system having social structure. The two components are 
not logically separable. Human groups occupy physical space and facili- 
ties in their interactions and adjustment to the environment. Linkages 
between physical and social elements are the specific point of reference 
in Park's well-known statement: 
It is because social relations are so 
frequently and so inevitably correlated 
with spatial relations; because physical 
distances, so frequently are, or seem to 
be, the indices of social distances, that 
statistics have any significance whatso- 
ever for sociology. And this is true, 
finally because it is only as social and 
psychical facts can be reduced to, or cor- 
related with, spatial facts that tbey can 
be measured at all.“ 
In summary, the fundamental hypothesis recognizes that urban social 
systems exist in physical settings and are housed in and characterized 
by material-cultural features. Such physical units are sociologically 
significant in that they limit, facilitate or condition social inter- 
action. Accordingly, certain aerial photographic information about the 
city should be meaningful for social science research because of the 
multiple interdependencies among physical and social elements. Evidence 
for this may be seen in a brief discussion of physical-spatial features 
identifiable in the photographic image as keys to an understanding of 
the social structure of the city. 
Related Research Evidence 
The literature of American sociology contains many references to 
research regarding empirical relationships between physical-material 
aspects of the city and several less tangible sociological and demo- 
graphic elements. Concentric circular zones? and distance gradients 
from the center of dominance are frequently representative of signifi- 
cant differences in social class, occupational status, ethnic groupings 
and other population characteristics, Zonal and gradient measures are 
also found to be associated with variations in social integration and 
deviant behavior. 
  
2. Robert E, Park, "The Urban Community as a Spatial Pattern and 
a Moral Order", in E. W, Burgess (ed.), The. Urban Community (Chicago: 
Press, 1926), pp. 3 - 18. 
3. For a comprehensive treatment of the concentric circular zonal 
hypothesis, see James A. Quinn, Human Ecology, New York: Prentice-Hall, 
Ines, 1950, Ch. VI.