WORKING GROUP 6 
LEIGHTY 
387 
subject may not be treated in an engineering manner. When literature is used 
in conjunction with airphotos, much more information may be obtained than 
when either are used alone. Usually this information is still too general for 
engineering planning and additional airphoto study is required. 
With airphotos of the area of interest and surrounding areas mounted as a 
mosaic and viewed from a distance, patterns and groups of patterns are easily 
seen. Each pattern represents adjustments of the physical situation to the en 
vironment. Similar patterns reflect similar physical situations and dissimilar 
patterns indicate dissimilar conditions. A physical situation could be any com 
bination of terrain configuration or composition, vegetative cover, moisture 
conditions, etc., but the combination must conform with the environment. 
Since this is an occurrence of nature it can be realized that patterns form at 
various levels or scales. A pattern perceived when viewing a large area may be 
established as a composition of many smaller patterns. Each of these may be 
further divided into patterns of lesser extent as the perspective is narrowed. 
When viewing a large area of terrain the patterns first discerned are those 
which have the greatest contrast to surrounding patterns. Thus, a meandering 
river area may present a completely different pattern from the adjacent up 
land. When viewed closer the pattern divides into active floodplain, abandoned 
channels, etc. These in turn divide into natural levees, terraces, floodplains, etc. 
Organization of terrain is implemented by first delineating major patterns 
and then minor patterns contained therein. Pattern boundaries may or may 
not be distinct because an infinite number of physical situations, which range 
from the simple to the complex, can exist. Transition from one pattern to anoth 
er could be a definite and sharp boundary or a zone where pattern features 
grade into each other. To aid delineation of patterns the interpreter should 
observe changes in topographic features, drainage features, vegetative condi 
tions, etc. 
From occurrence and distribution of patterns one can make a logical recon 
struction of the events leading to the present landscape configuration. This 
knowledge of terrain and an appreciation of the environmental influences 
concerning permafrost conditions provide general engineering information 
for problems concerning site selection, road location, material borrow areas, 
construction, etc. 
Local Analysis 
Upon completion of the terrain organization, a local analysis of the area of 
interest should be made to verify previous observations concerning composition 
of the terrain and permafrost conditions, and to refine previous information 
through detailed study. This involves detailed stereoscopic study of pattern 
elements within previously marked airphoto patterns. Pattern elements are 
landform, drainage, erosion, vegetation, photo tones, and special features. 
Irregularities in pattern elements lead to further division of an airphoto 
pattern.