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INTRODUCTION 
The conventional interpretation of aerial photographs is basically a 
stereoscopic study of the image pattern portraying a segment of the earth's 
surface and evaluation of its components. A systematic analysis of such image 
components as tonal characteristics, surface configuration, man-made features, 
or distribution and character of surface drainage channels, singles out the 
reliable indicators for the detection and identification of actual ground 
conditions. The surface configuration alone is often the most significant 
indicator of geomorphic processes responsible for the formation of present 
landscape, an important factor in photo interpretation of landforms (Jenkins 
et al 1946, Belcher 1948). Evaluation of topographic relief features 
associated with erosional and depositional processes also provides an 
excellent base for a systematic stratification of landscapes by the origin of 
their landforms and kind of surficial material (Ray 1960). The subdivision 
may be presented at a desired level of intensity. In the analysis of 
extensive land areas, for example, a stratification based on the repetitive 
occurrence of broad relief patterns allows a rapid subdivision of the land 
surface into general landscape units, that may be classified for example, as 
"rolling till plains", "bedrock-controlled hills", or "mountainous terrain", 
etc. 
To provide additional details, the components of this broad relief 
pattern may be separated as individual "hills", "ridges", "valleys", or 
"slopes", where the relief features usually reflect main physical 
characteristics of surficial material, its engineering properties and 
biological capability (Miles 1963, Gimbarzevsky 1973). 
TOPOGRAPHY AS AN AIR PHOTO INTERPRETATION ELEMENT 
Topography is a form of the land surface. When viewed on aerial 
photographs under a stereoscope the three-dimensional replica of a segment of 
the land surface exhibits a pattern of surface configuration that may be 
simply described as "level", "depressional", "hilly", etc. landscape. Each 
relief pattern is associated with a specific geomorphic process of deposition 
or erosion and reflects the origin and general character of the landscape. A 
systematic analysis of slopes, their degree of steepness, or particular 
arrangement of associated surface forms, their shape, size, and orientation, 
provides reliable diagnostic clues for the recognition of these geomorphic 
processes and for the interpretation of actual ground conditions from aerial 
photographs. 
RELIEF CLASSES 
Topography and associated relief features may be quantified and 
expressed in accordance with the areal extent and the mapping scale as "first" 
and "second" order topographic forms, or as "regional" and "local" forms of 
the land (Strahler 1967). For practical use of topography as a diagnostic