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well-developed, relatively wide plain (p), with shallow depressions and poorly 
drained accumulations of organic sediments. Also, such landforms, as sand and 
gravel terraces (t) fan-shaped accumulations of colluvial- and 
water-transported material at the lower slope position (c), or low ridges 
(natural levees) formed along the secondary channels (s), and many others, may 
be delineated where technically possible, at the mapping scale, as separate 
land units or land types. 
Microrelief Features 
A vertical exaggeration is an inherent feature of stereoscopic 
viewing. It permits a differentiation of minor changes in local topography 
and a detailed study of basic components of the relief pattern. Even minor 
forms of the land surface such as knolls, swales, blowouts or eroded channels, 
having 1 to 3 m vertical differences, that determine the relative "smoothness" 
or "roughness" of the area viewed, may be recognized and used as important 
diagnostic clues in air-photo analysis. The microrelief shown in Figure 4, 
for example, consists of randomly distributed semi-circular ridges, or "rims" 
(R) less than 10 m high, and some 2-3 m wide, enclosing flat areas from 30 to 
more than 150 m in diameter, that form "kettles" (K) within the rims. Such 
microrelief features are excellent indicators for the recognition of glacial 
landforms associated with the stagnant ice geomorphic process. The "rims" and 
"kettles" exhibit an unusual relief pattern and specific physical properties 
of the landscape, that are usually expressed as "complex" terrain units at the 
land system level or as separate land types in a detailed mapping. 
Other components of local relief, such as the intersection angles at 
change in slopes, the degree of slope equality on opposite sides of a ridge, 
the shape of minor knolls and depressions, their orientation pattern, or the 
relative smoothness and accordancy of ridge forms, are also important photo 
interpretation elements. In addition to the general characteristics of 
surface material within a recognized landform they may provide more specific 
qualitative information where required. A winding ridge, for example, may be 
easily recognized from its topographic shape as an esker, a glacio-fluvial 
landform containing water-sorted material, usually sand and gravel. The 
coarseness of dominant material of such landforms may be determined from the 
analysis of the microrelief features, such as angular relationship of this 
ridge form and the relative steepness of its slope. These micro-features may 
be best observed with a stereoscopic magnification or by using large-scale 
photographs, as shown in Figure 5. This large-scale (1:2,400) stereogram 
illustrates a kame landform, a small conical hill, about 12 m high, and 
containing some 30,000 m 3 of coarse sand and gravel. The lumpy microrelief of 
this conical hill, its sharp angular sides, and near-circular outline are the 
main identifying features for separation of kames from similar landforms, but 
containing a different material. 
CONCLUSION 
Topographic relief is probably the most common indicator of "ground 
conditions" in the conventional analysis of aerial photographs. In practical