Suitability Analysis

Suitability analysis is concerned with determining the most appropriate spatial pattern for future land uses according to specific requirements, preferences, or predictors of some activity. The analysis has its roots in the applications of hand-drawn, sieve-mapping overlay techniques used by landscape architects in the late 19th and early 20th centuries. In the 1960s, I. L. McHarg and others refined and advanced the overlay techniques by proposing a procedure that involved mapping data on the natural and human-made attributes of the environment and then presenting this information on individual, transparent maps using light to dark shading (low suitability to high suitability). When the maps were overlaid, the darkest areas then showed the most suitable parcels of land for particular types of land use.

Land suitability methods can be applied for tackling site selection problems or in the context of comprehensive planning. The aim of the site selection analysis is to identify the best site for a specific activity, such as a shopping center, an industrial plant, or a public school, given the set of potential or feasible locations (parcels of land). The problem is to rank or rate alternative sites based on their characteristics so that the best location can be identified. The comprehensive planning aims at identifying the best spatial pattern of land uses such as residential, industrial, commercial, and recreational. The procedure involves developing suitability maps for each land use based on criteria considered as important for the specific activity. The suitability maps are then overlaid to identify areas suitable for more than one land use.

The hand-drawn mapping technique for suitability analysis has been widely recognized as a precursor to the classical overlay procedures in geographic information systems (GIS). There are two fundamental classes of map combination (overlay) operations in GIS: Boolean overlay and weighted linear combination (WLC). Given a set of suitability maps and corresponding threshold values, the Boolean and operation results in classifying areas as suitable for a particular land use if each suitability map meets its threshold. Conversely, the Boolean OR operation identifies suitable areas as those that meet at least one suitability threshold value. The WLC approach involves standardization of the suitability maps, assigning the weights of relative importance to the suitability maps, and then combining the weights and standardized suitability maps to obtain an overall suitability score. The classical GIS approaches to [Page 2723]suitability analysis have recently been advanced by integrating GIS with multicriteria decision analysis methods.