Convergence of Experts’ Opinions on the Territory: The Spatial Delphi and the Spatial Shang
The judgments of a panel of experts are of extreme usefulness when, in front of a decision-making problem, quantitativ data are insufficient or completely absent. Experts’ opinions are helpful in forecasting contexts, for the detection of innovative solutions or for the verification and refinement of consensus on objectives or alternative scenarios.
The way the views are collected is crucial, and without a rigorous methodology any consultation process may become vain. In literature, there are many methods, but some are used for the ease of application rather than for their scientific properties. Methods such as focus group, face-to-face interview, or online questionnaire, are very popular but have quite important drawbacks.
Many of those disadvantages are overcome by the methods of the “Delphi family”, whose prototype is the Delphi method, which involves the repeated administration of questionnaires, narrowing the range of assessment uncertainty without generating errors that result from face-to-face interactions. To date, the Delphi technique has a very high number of applications and its success has produced a wide range of methods that are its variants.
This chapter describes two recent variants, called Spatial Delphi and Spatial Shang, applicable when consultations and consequent decisions concern matters of spatial location. The judgments of the experts are collected by means of points placed on a map, and the process of the convergence of opinions is built up through the use of simple geometric shapes (circles or rectangles). During the subsequent iterations of the procedure, the shapes become smaller and smaller, until to circumscribe a very small portion of territory that is the final solution to the research/decision problem.
After the discussion of the methods and the presentation of some practical applications, some possible evolutions are discussed that most likely will produce a future increase in the application of these techniques.
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