The
standardised factors of weighted linear combination
each express a perspective of suitability – the higher
the score, the more suitable. However, there is no
real threshold that can definitively allocate locations
to one of the two sets involved (areas to be chosen
and areas to be excluded). How are these
uncertainties to be accommodated in expressions of
decision risk? If these criteria really express
uncertainties, why are they combined through an
averaging process?
The surprising feature of multi-criteria evaluation
is that, despite its ubiquity in environmental
management, so little is understood of its character
in GIS. In the following sections we survey the issues
involved, and offer a perspective on a resolution
through the concept of fuzzy measures.