A Comparison of Two Basic Theories of Land Clas- 
sification and Their Adaptability to Regional Photo 
Interpretation T echniques # 
Gordon R . heath, i/. 5. Forest 
Service, Washington, D. C} 
Summary: The classification of land into units is useful in the analysis of 
regions. Systematic methods of describing terrain have been investigated 
by many men. Davis was the founder of a school which is widely accepted. 
Two other geographers took his fundamental principles and digressed in 
different directio?is. Fenneman used multiple subdivisions, dividing 
continents into physiographic provinces, sections and districts. Bowman 
divided physiographic provinces into topographic types. The latter has 
been the basis for land classification surveys in the United States for the 
last 35 years. It is particularly well suited to photo interpretation meth 
ods because the types are easily recognized on air photos, and because the 
types are homogeneous. However, physiographic subdivisions are very 
diverse and it is difficult to make generalizations about them which will 
apply to a specific site. Two partial regional keys, one adapted to Fenne- 
man’s methods and one adapted to Bowman's methods, illustrate the 
advantages and disadvantages of each method of regional study. The first 
keys out the Navajo Section of the Colorado Plateau. The second keys out 
the basin type of the same plateau. The two end products are compared for 
homogeneity and pertinence in the solution of photo interpretation prob 
lems. 
O NE OF the problems of regional photo regional level, and, when air photos are 
interpretation is to divide regions used, units which are well suited to study 
into units which will simplify analysis. If in air photography. Description and classi- 
it is desired to study single subjects, such fication, of course, are only initial steps 
as geology or industry, the decision is not in the analysis of the activities on the 
difficult and it is determined by the sub- earth. They help the geographer to group 
ject matter. But if the aim is to study all like things and related things together so 
of man’s activities the problem soon be- that their relationships may be better 
comes an analysis of how man uses the understood. Many schemes have been 
land, or man’s environment. This is ad- devised by geographers to accomplish this 
mittedly a complex subject and governed task, and two of the most promising are 
by many factors. The object of any re- presented in this paper and are compared, 
gional subdivision is to find the most ho- A brief account of the background behind 
mogeneous units, and, at the same time, the development of these methods will 
units which are significant at the broad help in understanding them. 
* A contribution of Commission VII, Photographic Interpretation, International Society of 
Photogrammetry. 
1 This article presents the view of the author and does not necessarily reflect the views of the 
U. S. Forest Service.