Using GIS for making decisions under uncertainty.

Using GIS for making decisions under uncertainty

Uncertainty can be defined as a state of being in doubt. GIS is primarily a decision support software that helps policy makers to take decisions regarding development and management with respect to geographical space. When there are several factors influencing the occurrence of an event, uncertainty arises regarding the outcome. Such situations fall under the ambit of "multi-criteria decision making".

Multi Criteria Analysis is a decision making is a tool developed for complex problems. It is used in a situation where multiple criteria are involved and confusion can arise when a logical, well-structured decision making process is not followed. In such cases, it becomes difficult to reach a consensus in a multi-disciplinary team. In such cases, each team makes a distinct identifiable contribution to arrive at a joint conclusion.

The theoretical basis of MCA
The various MCA methods in use are:

• Ranking
• Rating and 
• Pairwise comparison in the AHP (Analytic Heirarchy Process)

GIS can help in multi-criteria analysis (MCA) as an application for setting priorities. This complexity is addressed effectively by GIS as it can handle:

• Complex problems that require multi-disciplinary teams
• A diversity of stake holders
• Local, regional, continental and global scales
• Multiple parameters of assessment
• Uncertain and incomplete information

The Analytic Hierarchy Process (AHP) involves:

• Scoring methodology
• Categorizing empirical data and qualitative information

AHP helps organize the decision analysis in different levels. GIS tools and maps are utilized for making the decision. The various steps involved in GIS aided AHP are:

• Defining goals, setting priorities, criteria and indicators
• Prioritizing from indicators to criteria
• Hierarchization from criteria to goals and priorities

Quantitative prioritization is done using weighted spatial overlay analysis. This is done by:

• Collection of relevant spatial information data to use as indicators
• Categorizing indicators and attaching weights to them
• Overlaying weighted indicators to visualize each critera

Hierarchization from criteria to goals and priorities is done by prioritizing criteria by region. This is done by prioritizing regional criteria by:

• Assigning weighted values to qualitative criteria by experts
• Calculation of coefficients for each criteria weighted by region

The AHP method permits a structured discussion of complex problems by breaking them into different levels of importance. AHP methodology can be used in combination with GIS tools to help decision makers to analyse extensive information in maps to help in decision making. AHP helps to set priorities of options of different measurement parameters.

Thus GIS is an extremely useful tool for making decisions under uncertainty.