424 
3. The ferrallitic pole is not expressed through the forest 
cover. 
4. The same image processing has been applied and give ac 
ceptable results until a pixel size of 480 yi that is 9.60m. on the 
ground. 
2.3 Discussion 
1. The image processing allows to show an information on 
the forest cover which is related to soils organisation; this in 
formation was'nt easy to read (heterogeneity of the light, dis 
cordance with a topographic unit). 
2. The forest cover expresses only the most transformed, that 
is podzolic, part of the pedological system. 
3. The limits of the two domains (vegetal and pedological) 
are not precisely coincident; the shapes only may be compared. 
This lack of precision suggests several remarks: 
- the registration might not be good enough 
- future studies may be done to explain these discrepancies 
in terms of relative dynamics of soils and vegetation. 
- the structural information on soils lying in this aerial 
photography is more related to low-scale soils systems in 
formation than to large scale soils characteristics. 
4. This last remark will be tested when processing the whole 
picture as invite us the results of changes in resolution. 
3. CONCLUSION 
Structural information about superficial formation is present in 
the remotely sensed images studied. For the given examples, 
this information is expressed through a natural vegetal cover 
(primary or secondary) in terms of limits and domains. Using 
structural maps as reference, it is shown that 
1. The knowledge of deep weathered formations is necessary 
to establish the significance and the hierarchy between the 
different limits given by the vegetal cover. 
2. For a given pedological system, the most evoluted part of 
the mineral cover is visible, seen through the vegetal cover. 
3. The overlay between the pedological structural limits and 
the limits given by the vegetal cover is generally not precise; the 
relation is a global one; only shapes may be compared first. The 
study of the discrepancy can lead to further study of soils and 
vegetation relative dynamics. 
4. For the spectral bands used, the limits in the image define 
domains whose contents are not homogeneous: the 
methodology consists therefore on finding which combination 
of reflectance and (or) texture can best describe them. 
REFERENCES 
Boulet R. et al. 1981. L'écosystème forestier Guyanais. Etude 
et mise en valeur. № 4, CTFT. INRA, MUSEUM, 
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Dosso M. 1986. Analyse structurale d'une unité de modelé 
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Douala, Cameroun, Janvier 1986. MESRES, IBSRAM, 
ORSTOM. A paraître. 
Seyler F. 1986. Recherche méthodologique sur le traitement 
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