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3 RESULTS 
Decision problem may be resolved in several ways according to the way of thinking of the decision maker: 
-Restrictive hypothesis are introduced in such a way that the problem should be resolved using a classical method. 
-A multicriteria method based on models using both restrictive mathematical hypothesis and information acquired by 
the decision maker. 
When using the unique criterion approach, the problematic became at the same time choice, ranking and sorting. 
The drawbacks of the weighted sum "classical method" are: 
e sensitivity to scale transformation; In fact, if the proximity to roads criteria is expressed in km, then the result will be 
wrong (pixel score is divided by 1000). 
e criteria compensation: a pixel may have very bad scores on almost all the criteria but it may be compensated by a 
good evaluation on a highly weighted criterion. 
On the other hand the scale transformation and criteria compensation do not take part of ELECTRE approach. The 
major difficulty is, however, to give a right interpretation of the result. This would point out the conflict and 
' multicriteria features of the decision problem. 
Furthermore, the robustness analysis is very useful for choice of the initial values of the parameters. When the 
parameters are changed regarding their initial values, the results do not change and this represents a robust 
recommendation. 
4 CONCLUSION 
The objective of the study was not to compare these two methods since they are based on different mathematical bases. 
It was noted that the use of IDRISI modules facilitated the interpretation of the results. But this would never say that 
ELECTRE methods are not suitable for such a study, since these methods lead to an intermediate result between 
dominant relationship (very poor to be useful) and multi attribute utility function (very rich to be reliable). 
This study confirms that GIS constitutes a powerful tool for deterministic analysis of all the spatial data as well as the 
analysis of spatial multicriteria problems. 
Much work has been carried out on the development of both GIS and MCE techniques, but mostly in isolation. 
Besides the integration of GIS and ELECTRE methods this work would find out a wide thought on the relationship 
between GIS and multicriteria decision making. 
Integrating MCE with GIS for spatial decision -making purposes is both a worthwhile aim and one which will be of 
widespread utility to those involved in what is (and will continue to be) a mainstay application of GIS technology. 
This will in turn create the opportunity fore the increased use of GIS based technology as the bases of spatial decision 
support systems. 
It is important to note , however, that GIS and MCE techniques are merely tools which provide a means to an end. 
Without the knowledge and expertise of the operator and decision-maker, and without appropriate data, such tools 
would be useless. 
Nevertheless, GIS-MCE applications appear to represent potentially fruitful areas for further research and development. 
5 REFERENCES 
S. J. Carver. Integrating multicriteria evaluation with geographical information systems. International Journal of 
Geographical Information Systems, V ol. 5, No. 3, 321-339, 1991. 
H. Daoud Brikci. Intégration de l'analyse multicritére dans les systémes d'information géographiques: développement 
d'un prototype MaplInfo-Electre. Thése de magister, Centre National des Techniques Spatiales, 1997. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 311