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SPECTRAL ANALYSIS OF SATELLITE DATA AND THEIR ASSESSMENT BY DIFFRACTOMETRIC 
ANALYSIS. CASE OF SAMPLES OF A TEST ZONE OF THE SOUTH OF ALGERIA 
A.BELHADJ-AISSA*, Y.SMARA* and P.BILDGEN** 
* Laboratoire de Traitement d'Images,U.S.T.H.B/Institut d'Electronique 
BP 32 El-Alia Bab-Ezzouar ALGER ALGERIE 
** Laboratoire de Géochimie et Métallogénie, Université PARIS VI 
4, Place Jussieu 75252 PARIS FRANCE 
ABSTRACT 
This paper describes a methodology using, on one hand, a spectral 
analysis of states of surfaces of soils from a region of the south of Algeria 
by using color composite imagery with judicious selected channels, and, on 
other hand, an assessment of this study by a diffractometric analysis, of 
samples taken on a test site called OUM DELOUA,near the town Laghouat 
(Algeria) , has been carried out for a knowledge of mineral constituents of 
studied soils. The obtained results by the traced spectral signatures allowed 
us to identify approximatively the big themes existing in the region of study. 
As to the diffractometric analysis it allowed us a more accurate 
quantification of the elements, and this thanks to the mineralogie information 
extracted from samples analysis which distinguish soils very closely at a 
first view. 
KEYS WORDS:Remote sensing, Spectral signature, diffractometric analysis, arid 
and semi-arid zones. 
INTRODUCTION 
In the field of remote sensing of arid and semi-arid regions, the three 
factors the most influent which affect the measured brigthness by satellites 
sensors are: 
- Roughness (clumps of vegetation, microrelief created by eolian erosion). 
- Mineral constituents ( sand, limestone,etc) . 
- Color of soils. 
In order to analyse and to caracterize states of soils surfaces , the 
proposed methodology is based on techniques of spectral and diffractometric 
analysis and their contribution for the discrimination and the caracterization 
of surfaces . The interaction and the complementarity of the two methods allow 
a better identification at level of samples of study. An extrapolation of 
these results can be carried out with the help of documents of maps and the 
ground studies. 
In this paper,we have carried out an extraction of spectral signatures of 
different themes identified from a résultante image of a color composite 
imagery corresponding at three original channels. A first interpretation of 
results has been determined on the base of the channel ( channel TM5 ) 
whichdistinguishes the best the themes. However, this study does not allow us 
to stand out all the themes existing on the ground. 
In order to improve our study, we have carried out a quantitative 
analysis localised at level of samples taken on a test site . This method 
consists on diffractometric analysis which, from a spectral mineral 
composition of taken samples, allows us the assessment of spectral signatures 
curves of pixels corresponding at exo-atmospheric reflectance data from 
Landsat TM images.