AA 
| 
The use of combined ELECTRE multicriteria methods 
and raster GIS for the spatial decision support. 
H. Daoud Brikci, A. Mendas & M. A. Trache 
Research scientists at Geomatic Laboratory 
National Centre of Spatial Techniques 
BP 13, Arzew 31200, Algeria 
Commission VII , Working Group 2 
KEY WORDS: ELECTRE, GIS, MCE, Multicriteria, SDSS. 
ABSTRACT 
The geographical information systems (GIS) provide the decision-maker with a powerful set of tools for the manipulation and 
analysis of spatial information. The functionality of GIS is, however, limited to certain deterministic analyses in key application 
areas such as spatial search. For problems pertaining to the territory, there are, generally, several alternatives that can satisfy the 
objectives. Each alternative has its own costs and effects which need to be evaluated. 
Landsuitability evaluation has to face two major difficulties. First, there is a huge number of alternatives because each different 
coordinate is a possible solution (raster representation). Second, the decision making process is generally based on different 
criteria, which can be defined on a quantitative or a qualitative scale. In this context, this paper explore the possibility of improving 
communication between land use and decision makers, using an interactive system combining GIS potentiality and multicriteria 
evaluation (MCE) techniques. 
An example application based on the search for suitable sites for irrigation in Tlemcen (Algeria) using IDRISI (raster GIS) and 
ELECTRE (MCE methods) is included. The potential integration of GIS-MCE forms an interesting avenue to evolve GIS towards a 
true spatial decision support systems (SDSS). 
RESUME 
Les systèmes d'information géographique (SIG) fournissent au décideur des outils puissants de manipulation et d'analyse des 
données spatiales. 
Cependant, les fonctionnalités qui y sont implantées se limitent à de simples analyses de type déterministique. Les problèmes 
relatifs au territoire impliquent, généralement, plusieures actions où chacune peut répondre aux objectifs fixés et où chacune a ses 
propres coûts et conséquenses qu'il s'agit d'évaluer. 
L'évaluation de l'adéquation du sol à un usage donné doit faire face à deux difficultés majeures. Le grand nombre d'alternatives 
possibles, car chaque position est une solution potentielle (représentation matricielle). Le processus de prise de décision est en 
général basé sur différents critères, lesquels peuvent se rapporter à des échelles qualitatives ou quantitatives. Dans ce contexte, ce 
papier explore la possibilité d'améliorer l'interface décideur/utilisation du sol en utilisant un system interactive combinant les 
potentialités du SIG et les techniques d'analyse multicritère. 
Un exemple d'application concernant la recherche de sites convenant à l'irrigation dans la région de Tlemcen (Algérie) est présenté, 
en utilisant les potentialités du SIG IDRISI et les méthodes multicritères ELECTRE. 
Le potentiel d'intégration SIG-ELECTRE constitue une voie intéressante pour faire évoluer les SIG vers de véritables systèmes 
d'aide à la décision à référence spatial (SADRS). 
MOTS CLES: ELECTRE, Multicritère, SADRS, SIG. 
1.INTRODUCTION [R. Eastman and al., 1993], [pereira and Duckstein, 1993] and 
[Vidal et al, 1994] integrated full aggregated multicriteria 
Until now, the spatial decision making and the integration of procedures into a raster GIS. 
multicriteria into a GIS are less used. The most significant 
work in this field was that of Eastman and al. [1993] which — However, the different studies done until now showed that this 
provide the new version of IDRISI GIS 4.1 by a decision approach was not reliable (A. Scharlig, 1985) but it is still 
support analytical ring. It includes multicriteria evaluation used since the partial aggregation (outranking) approach 
based on the weighted sum using Analytical Hierarchy Process cumbersome due to the intercomparison of all the alternatives 
methods. It is the only one which includes analytical rings of (actions) which represents, in the case of an image (pixels), 
decision aid especially the multicriteria analysis. about 100 million of operations (F. Joerin, 1995). 
86 International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
criter 
formu 
(9. 
Giver 
select 
most 
he s 
probl 
altern 
intrin 
alterr 
The 1 
probi 
the « 
categ 
proto 
data 
meth 
in GI 
as th