Suitability Analysis is the process and procedures used to establish the suitability of a system – that is, the ability of a system to meet the needs of a stakeholder or other user. Before GIS was widely used in the mid to late 20th century, city planners communicated their suitability analysis ideas by laying transparencies in increasing darkness over maps of the present conditions. This technique's descendant is used in a GIS application called multicriteria decision analysis. In the 1960s, a mechanism called the ecological inventory process was developed to document existing surrounding land conditions to help inform the analysis for the land in question. These mechanisms were computerized upon the advent of computers due to inefficiencies in the methods, such as the inability to overlay a large number of transparencies. In order to feed a growing population that is pushing on the ability to extensively farm, suitability analysis is becoming more necessary to utilize the most productive land to its fullest potential, matching the needs of the plants more carefully to the existing assets in the environment. This technique is known as precision farming. Suitability analysis can also be used to track and label potential hazards, like earthquakes, contamination, or even crime. It can also be used to locate advantageous locations for commercial centers.
Suitability in GIS context
Suitability analysis in a GIS context is a geographic, or GIS-based process used to determine the appropriateness of a given area for a particular use. The basic premise of GIS suitability analysis is that each aspect of the landscape has intrinsic characteristics that are to some degree either suitable or unsuitable for the activities being planned. Suitability is determined through systematic, multi-factor analysis of the different aspects of the terrain. Model inputs include a variety of physical, cultural, and economic factors. The results are often displayed on a map that is used to highlight areas from high to low suitability. A GIS suitability model typically answers the question, "Where is the best location?" — whether it involves finding the best location for a new road or pipeline, a new housing development, or a retail store. For instance, a commercial developer building a new retail store may take into consideration distance to major highways and any competitors' stores, then combine the results with land use, population density, and consumer spending data to decide on the best location for that store.
GIS Applications
Land use analysis: Land-use suitability analysis requires the use of GIS in order to survey geographical suitability. This process can be viewed through the techno-positivist and the socio-political, public engagement perspectives. Within the analysis of suitability there are also needed factors regarding economic opportunity costs and social implications within particular areas of land. There has been critique in the role that both of these aspects of careful spatial planning entail. The instrumental approach to spatial analysis can either be seen as a tool, or as a main plan when it comes to suitability. This brings up the theoretical questions of space, place, and the social construction of both. Land-Use suitability requires a multicriteria analysis, which is allows assumptive and theoretical mapping to become actualized. Most jurisdictions use land suitability analysis for site selection, impact studies, and land use planning.
Retail site selection: Suitability analysis is critical for both marketing and merchandising purposes, as well as for choosing new retail locations.
Agriculture
Defense
Crime analysis
Town Planning
Wildlife: The identification of physical structures, natural habitats, and the relationship between the two and the environmental impacts of that. This allows for the optimization between the relationship of enhancing wildlife while also allowing for man made development.
Possibility Space
The Possibility Space is a framework that allows for the analysis of all possible consequences and benefits of a suitability analysis. This is created through geometrical data analysis conducted in real time with technological land mapping, allowing for the development of multiple combinations of suitability. Physically it is a visual interactive database that allows for a holistic composition of suitability.
Methods
Gestalt method: The area is mapped and similar regions are identified. Additional maps are drawn for each homogeneous location representing each possible land use, which are compared and analyzed to ascertain the best possible land use. However, this method is not very commonly used because it requires intense knowledge of the place in question, usually only acquired when the planner has the opportunity to live in the space and dedicate an ample amount of time to it. It is also more difficult to communicate it effectively.
Ordinal combination method: The area is mapped according to qualities of the land, including slope, soil type, vegetation, climate, etc., and each quality has a rating associated with it corresponding to its value. Therefore, the land use is determined by the suitability rating given to it based on the comparable qualities of other areas. Some shortfalls include that the rating is subjective to the expert, and each rating must be done on the same scale to be comparable.
Linear combination method: The rated qualities of the ordinal combination method are compared with different weights with the most weight put on the most important value and the least weight put on the least important, though each rating is put on the same interval scale.
Values suitability analysis:Human values are taken into account with similar weight to quantifiable costs and benefits in deciding land suitability. This is done frequently in deciding incorporation of open spaces and their management techniques.
AHP : A method that determines the weight of each component of the land making it favorable or unfavorable for each use. It has the capability to identify inconsistencies in judgement.
Results
When suitability analyses are done, several different usability options may be found for the same section of land. This can be advantageous or limiting. If the land is found suitable for two or more uses that can be combined, the land uses are found compatible. An example of this may be a building with businesses on the bottom floor with residences on upper floors. Compatible land uses result in a win-win development; a need for more commerce is met while meeting a need for more housing, while also keeping people on the street all day, thereby reducing the probability of crime. Conflicting land use occurs when a piece of land can be used only for one use or the other. This is exemplified by a piece of land that can either be used as agricultural land or developed into a housing tract—should the land be developed, it can no longer be used for agriculture. The suitability analysis comes back into play here by helping planners prioritize which need is greater.
