TM 5-852-2/AFR 88-19, Vol. 2
or maps, can be merged effectively into the "envi-
terrain.
ronmental data base" necessary to complete the final
(3) Considerable use can be made of airphotos
interpretive phase of the study.
during the design phases for structures, large
(c) Upon completion of this second phase of
installations and transportation systems. However,
study, the analysis team should consider going into
the designer needs detailed quantitative data such as
the field to check its work and to iron out any
composition, profile or stratigraphic characteristics,
remaining trouble spots. The field correlation of the
thickness and kind of mantle on bedrock, densities,
original photo analysis by the team members is an
bearing strength, surface and subsurface moisture,
extremely valuable exercise, which invariably results
presence and type of frost-susceptible materials,
in an upgrading of individual and team capabilities.
thickness of the active layer, ice/soil relationships in
(d) Finally, the interpretive phase of the study
the permanently frozen subsurface, and location and
is reached where all acquired information is
type of organic material, if present. The present
interpreted in the light of a specific problem or
state of the art does not permit obtaining
question. Only then has enough pertinent informa-
quantitative data on any of these items by photo
tion been assembled to warrant the answering of the
analysis or any other remote sensing means.
primary question posed about the study area.
However, the detailed analytical study of photo
e. Site evaluation process. Understanding the re-
patterns will result in mapping the type, distribution,
lationship between the visible indicators of perma-
and general characteristics of soils and rocks;
frost and severe frost activity on the aerial photog-
determining the complexity and uniformity of a
raphy and actual ground conditions will allow the
deposit; determining the location and extent of
team to obtain a considerable amount of accurate
surface water and suspected occurrences of high
and detailed information through the photographic
subsurface moisture; discovering general permafrost
analysis process. Detailed stereoscopic study of high
location and characteristics; determining the
quality aerial photos assembled into a stereoscopic
location and general magnitude of frost activity in
photomosaic will result in locating, identifying, and
the active zones; and identifying and locating areas
evaluating many of the features necessary to
requiring concentrated attention for successful
determining ice-soil relationships and the thermal
construction. Since the quantitative data can only
regime. Chief among these are topographic position,
result from field sampling and laboratory testing, the
parent materials, surface drainage, vegetation,
photos play an important role in planning the field
exposure to solar energy, and above all, the well-
sampling program.
established indicators related to permafrost and frost
(4) Individual factor overlays are presented that
action phenomena. Some of these indicators are
result after the photointerpreter has delineated
polygons, button drainage, pingos, frost boils,
photo patterns on the airphoto mosaic through the
altiplanation features, solifluction lobes and strips,
processes of stereoscopic viewing and analysis.
stone rings, etc.
Overlays depicting land forms, drainage, surface
(1) Airphoto derived information is recorded
materials, vegetation, land use, and special factors
directly on a series of Mylar or acetate overlays
such as permafrost can all be created separately.
depicting categories such as landforms/soils/rocks,
Examples of some of these overlays, prepared from
drainage, vegetation and associated wildlife habitat,
the photomosaic (fig. 3-5), are presented as figure
land use and transportation, and frost/permafrost.
3-6.
(a) Drainage overlay. The various patterns of
These provide an environmental data base and are
useful in all stages of project planning and
drainage evident on this overlay reflect conditions of
development.
the bedrock and surface materials composing the
(2) For purposes of locating or siting, the
terrain. All of the landform and permafrost
airphoto analysis technique offers much to the
boundaries on the following two overlays corre-
location engineer in terms of the following:
spond to changes in the patterns of drainage. This
--A basis for understanding an area in regard to
drainage factor tends to be one of the most
criteria governing the type of structure to be built.
important factors to be mapped in any photo
--Information about likely problems because of
analysis study. Also, it should be the first factor to
the environmental stresses present.
be mapped because it forces an analyst or team of
--A basis for predicting environmental impacts
analysts to view the entire area stereoscopically to
likely to result during construction.
delineate all the fine drainage detail. This, in turn,
In the Arctic these are extremely important because
provides a necessary initial familiarity with the entire
of the often very sensitive thermal regime of the
area.
3-10
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