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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
permanently frozen zone cause the majority of engineering difficulties in the 
Arctic. Hence, the importance of obtaining information in advance of utiliz 
ation of the terrain. 
Organization of Terrain from Airphotos 
When organizing terrain to obtain information for solution of an engineer 
ing problem, it is first necessary to determine its gross nature in the area of 
interest and then proceed to minute features. The approach should always be 
from the general to the detailed and the objective should be to bring order or 
organization to the natural features imaged. The importance of literature in 
obtaining generalized information should not be overlooked, even though the 
Fig. 4. Organization of terrain of an area along the Alaskan Arctic Slope. Three major 
patterns exist in this area - the mature river valley, the coastal offshore bar and the sandstone 
(Ss) and shale (Sh) upland. Terraces and floodplains flank the meandering stream which 
evidences some bedrock control along its course and gradient by the valley width and channel 
configuration. Only a very narrow coastal beach exists except for the offshore bar and depos 
its near the river mouth. In the upland, the resistant, steeply dipping sandstone ridges are well 
defined compared to the rounded shale slopes. Colluvium and slopewash (Col) mantle the 
steeper shale slopes and are easily distinguished by the dense network of erosion and drainage 
patterns. Polygon degradation (P.D.) is evidenced in some large level areas of shale and col 
luvial soils at the base of colluvial slopes. This and other information obtained from the air 
photo mosaic can be applied to preliminary planning for site selection, road location, material 
borrow areas, construction, etc.