Full text: Remote sensing for resources development and environmental management (Vol. 1)

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Use of remote sensing for regional mapping of soil organisation data 
Application in Brittany (France) and French Guiana 
M.Dosso 
Centre Scientifique IBM France, Paris 
F.Seyler 
Société Européenne de Propulsion, Paris, France 
ABSTRACT: Two analysis showing the coincidence between soils organisation data and remotely sensed images are 
presented, the hrst one in Brittany and the second one in french Guiana. 
RESUME: Deux analyses montrant la coïncidence entre des données d'organisation des sols et des images de télédétection 
sont présentées, la première en Bretagne et la seconde en Guyane française. ^ 
The aim of this study, which started in 1983, is to fmd and then 
use the information related to local soils organisation data 
obtained from remotely sensed images, to extend the local 
knowledge and mapping of soils, at a regional scale. 
This long term research is being carried out; the first results 
are presented. 
i. BRITTANY 
1.1. Situation of the study and general methodology 
The presented work concerns a 32 ha. area in central Brittany 
(France). Its morphology is made of a plateau, a northern 
slope and a downstream flat level. It is constituted by a 
Gedinnian and inf. Siegennian anticlinal of schists and 
quartzites, and covered with heath and fernery. 
This work w r as made in two parts 
1.1.1. A ground reference constitution 
1. Concerning the superficial formations organisation 
This organisation is modelised threw: 
Ground observations of 165 profiles and 9 trenches. The 
different organisations volumes are described, the limits 
between the volumes are geometrically drawn, allowing an 
analysis of their relations. 
Microscopical and chemical analysis have load us to precise 
the characterizations, and to determine some processes of 
différenciation and their chronology. 
The limits between the different organisations volumes have 
been spatially followed by numerous observations. 
2. Concerning the distribution of vegetation: 
A map of the spatial repartition of the main vegetal unities 
has been performed, through the interpretation of an aerial 
infra-red photography, and through ponctuai observations 
inside the homogeneous regions and on their limits. Each limit 
of this map has been analysed from the point of it significance 
depending on vegetal competition, human impact, or relation 
with the superficial formations. 
1.1.2. Image study 
The infra-red photography was obtained during an aerial mis 
sion required to be at the scale of 1/20 000. This photography 
was digitised by a microdensitometer, in two different images, 
in such a way that a pixel represents a square at the soil surface 
of 50x50 cm for the first image, and of 90x90 cm for the second 
one; each was digitised in three channels, red, green, blue for the 
reflectances in infra-red, red, and green respectively. These 
images were prepared by contrast enhancement treatments. The 
cadastre, the map obtained by the study of superficial for 
mations and the vegetation map were registered on both ima 
ges. The treatments tested with the aim of expressing the 
information related to the ground reference were of two kinds: 
1. Statistical treatments on the reflectances. 
2. Textural treatments. 
1.2. The ground reference . 
The ground reference study led us to propose three main results. 
1. The first one concerns the organisation of the alteritic for 
mations in three domains. The limit between the first two, 
developped on the plateau and the slope, is of geological sort, 
it shares a domain with weak weathering on hard grey schists, 
and a domain with a very developped and deep weathering, on 
more alterable schists alternating with quartzite. The limit 
between these two domains and the third one, lying 
downstream, is the one of an hydromorphic transformation, 
which affects the two previous domains by a mobilisation and 
a concentration of iron and clays. A localised zone on the pla 
teau is equally affected by this transformation, which results 
from the beating of the permanent water sheet. 
2. The second one concerns the relations between the surface 
différenciations and the structure of the alteritic formations 
described above. In facts, the pedological limits reflect this 
profond structure. Some limits are purely superficial 
différenciation ones, but by the study of the alteritic structure, 
we are allowed to define, among these superficial limits, which 
one are revealing the internal structure of the whole volume of 
the superficial formations. On the map presented below, we 
have overmarked these structural limits. 
Figure 1 : Map showing the structural limits of superficial for 
mations
	        
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