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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
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