Uncertainties in spatial decision, a policy-maker point of view

While public decisions concern the society or some collectivities, they are formalised by the policy-makers. Policy-makers face wide-spread types of information, each one of them having their own uncertainties associated with. The particularity of public decision-makers is to deal with those uncertainties. On the contrary, scientists limit the uncertainties in their experiments by enunciating hypotheses. In any decisional process, decision taking is based on a decision analysis phase which relies on a documentation/information phase. It is then followed by the implementation and the evaluation phases. The foundation of the documentation/information step is composed by three interconnected aspects: data, issue and context. Decision being the act of making up one’s mind can be linked to space or influenced by space or not at all related to space. Public decisions are all spatially referenced if not spatially induced since they apply to a certain territory. The territorial scale of application of a decision intervene not only in the choice of data and analysis, but also on the way the issue is expressed and on the degree of certainty acceptable for decision-makers at the different steps of the decision process. This contribution approaches the uncertainties not from a data perspective, but from the decision-making process point of view. After defining the concepts of spatial and public decisions, the different types of uncertainties and their consequences are presented using a generic model of decision processes.