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Transactions of the Symposium on Photo Interpretation

purposes, and techniques of pedological analysis [Buringh 1954, Veenenbos,
1956] would aid mapping. Therefore it seems clear that it would benefit ground
surveyors and photo interpreters if landscape units played a larger part in the
mapping, description and classification of Soil Series.
The practical value of mapping units based upon landscape units may be
questioned by soil surveyors accustomed to general-purpose classifications
based on profile characteristics. However, recent appraisals of soil surveys in
Australia [Gibbons, 1961] have illustrated that surveys based upon general-
purpose classifications may themselves have limited value. In consequence
Gibbons puts forward two approaches aimed at making soil surveys more
valuable. The first approach is to improve the general-purpose classification
by selecting better key criteria and then to combine this improved classification
with other environmental features in the mapping programme. Thus he
suggests that “the use of the other environmental variables such as climate,
geology, topography and vegetation, by defining and describing the compo
nents of the ecosystem is more likely to achieve the varied purposes of a soil
survey than would soil survey alone”. If the ecosystem approach be adopted
there is ample evidence to show that aerial survey can contribute to the speed
and efficiency of the work.
The second approach advocated is that specialist classifications should be
developed for known purposes over limited areas. In these circumstances the
ground surveyor must seek correlations between mappable soil features and soil
factors relevant to land use. Likewise the photo interpreter must search for
visual key criteria related to the purpose of the survey e.g. the use of Gilgai
patterns to establish areas with soils of low permeability and high compaction,
[Binnie, Deacon and Gourly, 1956]. In many instances it is likely that the
key criteria will lie in the minor details of colour tones, drainage patterns and
vegetation patterns, which are often so subtle that they are easily passed over.
The significance of these micro-features may not be recognised owing to lack
of experience or simply inability to visualise the object concerned [Belcher,
1959]. In the case of soil studies lack of recognition may also stem from the
emphasis placed upon the soil profile in soil studies. Many soil surveyors find it
easier to think in terms of vertical profiles rather than the surface patterns
which soils present in plan view. Indeed it is probable that in many instances
there is insufficient detailed knowledge of surface patterns of soils (and other
landscape features) to allow adequate assessment of the meaning of patterns of
micro-features seen on photographs. When soil maps and aerial photographs
for the same area are compared they often show broad agreement but lack
correspondence when matters of detail are studied. This lack of correspondence
may arise in two ways. First, the soil map is usually not sufficiently detailed to
show the intricate patterns which photographs reveal. Thus generalised
boundaries occurring on soil maps do not accord with detailed boundaries
which may be seen on photos. Secondly, the boundaries on soil maps may be
unrealistic in that they are related to subjective groupings of soil individuals
rather than the soil individuals themselves. For example British surveys group