an introductory overview to multi criteria evaluation geog 5161: research design professor kenneth...
TRANSCRIPT
An Introductory An Introductory Overview to Multi Overview to Multi
Criteria Evaluation Criteria Evaluation
GEOG 5161: Research Design
Professor Kenneth E. Foote
Petra Norlund
2010
OutlineOutline
• 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?
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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
IntroductionIntroduction• 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
BackgroundBackground• 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 Post computers: Basic GIS ApproachesApproaches
• Polygon overlay (Boolean logic)Example uses:
• Nuclear waste disposal sites
• Street routing
DefinitionsDefinitions• 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)
What is it used for?What is it used for?
• Decision making• Dispute resolution• Water resource management• Sustainable development• etc
Principles of MCEPrinciples of MCE• Methodology:
1. Determine criteria (factors/constraints) to be included
2. Determining the weights for each factor
3. Sensitivity analysis of results
11stst Step: Determine the Step: Determine the criteria to be includedcriteria 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
siteCriteria used: River Urban Forest Accumulated water flow Existing reservoir Watershed boundary City Hydraulic head Undulation
Determine the weightsDetermine 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.
Sensitivity analysisSensitivity 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 consMCE – 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!