An Introductory Overview to Multi Criteria Evaluation GEOG 5161: Research Design Professor Kenneth E. Foote Petra Norlund 2010

Outline Introduction and Background Definitions What is multi criteria evaluation? How and when is it useful? How does it work? Case study to show how it is implemented Pros and cons of the method. Why should we use it?

Kärt barn har många namn... Multi Criteria Analysis Multi Criteria Evaluation (MCE) Multi Criteria Preference Analysis Multi Criteria Decision Making Multi Objective Evaluation These methods are essentially one and the same! MCE = Multi-criteria evaluation is primarily concerned with how to combine the information from several criteria to form a single index of evaluation

Introduction Land is a scarce resource: Identifying suitability for Where to build a dam Water flow Mountainous? Where to place a hospital Costs Access Greatest need Criteria can be based on human or physical geography factors

Background Early methods (pre computers): Ian McHarg (1969) Design with Nature Used for suitability analysis Tracing paper overlays Limited to simple Boolean analysis: AND, OR, NOT See demo!

Post computers: Basic GIS Approaches Polygon overlay (Boolean logic) Example uses: Nuclear waste disposal sites Street routing

Definitions Decisions: a choice between alternatives Criterion: some basis for a decision. Two main classes: Factor : enhances or detracts from the suitability of a land use alternative (e.g. distance from a road) Constraint : limits the alternatives Goal or target: some characteristic that the solution must possess (a positive constraint)

The Basics

What is it used for? Decision making Dispute resolution Water resource management Sustainable development etc

Principles of MCE Methodology: 1.Determine criteria (factors/constraints) to be included 2.Determining the weights for each factor 3.Sensitivity analysis of results

1 st Step: Determine the criteria to be included Criteria determine the alternatives Oversimplification of the decision problem could lead to too few criteria being used Using a large number of criteria reduces the influence of any one criteria Often proxies must be used since the criteria of interest may not be determinable

Example: Case study of a suitable dam and reservoir site Criteria used: River Urban Forest Accumulated water flow Existing reservoir Watershed boundary City Hydraulic head Undulation

Determine the weights A decision is the result of a comparison of one or more alternatives with respect to one or more criteria that we consider relevant for the task at hand. Among the relevant criteria we consider some as more important and some as less important; this is equivalent to assigning weights to the criterion according to their relative importance.

2 nd stage, assigning weights

Weights assigned using AHP

Weights assigned using the Rank Order method

Sensitivity analysis → sensitivity analysis : vary the scores/weights of the factors to determine the sensitivity of the solution to minor changes Choice of criteria (e.g. why included?) Assesses the reliability of data: how stable is the final result? Choice for weighting factors is subjective Will the overall solution change if you use other weighing factors?

MCE – pros and cons Cons: Dynamic problems strongly simplified into a linear model Static, lacks the time dimension Controversial method – too subjective? Pros: Gives a structured and traceable analysis. Possibility to use different evaluation factors makes it a good tool for discussion. Copes with large amounts of information. It works!

Conclusion Good for any complex decision problem. Allows decision makers to show their thinking. Useful in any GIS analysis where several criteria are incorporated. Includes the ability to weigh criteria. Often used for land allocation.