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MCE:Criter ia Development and

the Boolean Approach

Exerc ise 2-7

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MCE

Multi-criteria Evaluation

a common method for assessing and

aggregating many criteria.

Decision will not be based on a single criteriabut a combination.

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Types of MCE

MCE

Boolean

Aggregation

Method

WLC

(Weighted

Linear

Combination)

OWC

(Ordered

Weighted

Averaging)

Exercise 2-7 Exercise 2-8 Exercise 2-9

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Objective of the Exercises

single hypothetical suitability problem.

to find the most suitable areasfor residential

development in the town of Westborough,

Massachusetts, USA. The town is located very near two large

metropolitan areas and is a prime location for

residential (semi-rural) development.

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Considerations and Requirements..

Developersprime location (areas that best suit their needsallocated for residential development).

environmental groupswhere new development will or will notoccur. The environmentally-mixed landscape of Westborough includes

many areas that should be preserved as open space and forwildlife.

The town regulationslimit land for development.

All these considerations must be incorporated into the decisionmaking processHence MCE

The goal is to explore potential suitable areasfor residential development for the town of

Westborough: areas that best meet the needs ofall groups involved.

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Considerations

Constraints Factors

LANDCON

WATERCON

MCELANDUSE

TOWNDIST SLOPES

WATERDIST DEVELOPDIST

ROADDIST

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Constraints

YES / NO ? TRUE / FASLE 1 / 0

Constraints are those Boolean criteria that constrain

(i.e., limit) our analysis to particular geographic

regions.

Constraints are always Boolean images.

In this Example: The constraints differentiate areas

that we can consider suitable for residentialdevelopment from those that cannot be considered

suitable under any conditions.

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Factors

Factors are criteria that define some degree

of suitability for all geographic regions.

They define areas or alternatives in terms of

a continuous measure of suitability. Individual factor scores may either enhance

(with high scores) or detract from (with low

scores) the overall suitability of an alternative.

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MCE:Criter ia Development and

the Boolean Approach

STEPS OF THE EXERCISE

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a) Path Setup

Change the Data Paths (under the file menu)

so the folder Idrisi32 Tutorial / MCE is set as

the working folder.

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b) Display of the Image

Display the image MCELANDUSE using the

user-defined MCELANDUSE palette.

Choose to display the legend and title map

components. Use Add Layer to add the streams layer

MCESTREAMS with the user-defined BLUE

symbol file

Add roads layer MCEROADS with the

uniform black symbol file.

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c) Water

Display the image MCEWATER with the Qualitative palette.

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d) Water Constraints

Display the image WATERCON with the Qualitative palette.

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e) Land use Contraints

Observe MCELANDUSE.

Clearly some of these categories will be

unavailable for residential development.

Areas that are already developed,

water bodies,

and large transportation corridors

cannot be considered suitable to any degree.

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f)

Display LANDCON, a Boolean image

produced from MCELANDUSE

Areas suitable1

unsuitable for residential development0.

Suitable categoriesCropland

PastureForest

Open Undeveloped

Unsuitable CategoriesOpen Developed

Multifamily residential

Small Lots ResidentialMed Lots Residentials

Large Lot Residential

Commercial

Industrial

Transportation

Open Water

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g)

Examine the images ROADDIST,

TOWNDIST, and SLOPES using the IDRISI

standard palette.

Display MCELANDUSE with the Qualitativepalette.

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ROADDIST

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TOWNDIST

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SLOPES

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h)

Examine the images WATERDIST and

DEVELOPDIST using the IDRISI standard

palette.

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WATERDIST

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DEVELOPDIST

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Boolean Approach for MCE.

All criteria (constraints and factors) will be

standardized to Boolean values (0 and 1).

method of aggregation will be Boolean

intersection (multiplication of criteria). This is the most common & Simplest GIS

method of MCE.

Severely limit analysis and constrain resultantland allocation choices.

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Boolean Standardization of Factors

"crisp" or "hard" decision

how continuous data (e.g., slopes) can be

effectively reduced to Boolean values.

All of the continuous factors developedpreviously must be reduced to Boolean

constraints.

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Landuse Factor

Of the four landuse types available for development,

forested and open undeveloped lands are the least

expensive and will be considered equally suitable by

developers, while all other land will be considered

completely unsuitable.

Suitable categoriesCropland

PastureForest

Open Undeveloped

Unsuitable CategoriesOpen Developed

Multifamily residential

Small Lots ResidentialMed Lots Residentials

Large Lot Residential

Commercial

Industrial

Transportation

Open Water

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Distance from Roads Factor

To keep costs of development down, areas

closer to roads are considered more suitable

than those that are distant.

Suitable categoriesareas less than 400 meters

from any road

Unsuitable Categories

equal to or beyond 400 meters

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Distance to Town Center Factor

Homes built close to the town center will yield

higher revenue for developers.

Distance from the town center is a function of

travel time on area roads.

Suitable categoriesless than 10

minutes or 400 GCEs of the

town center

Unsuitable Categories400 GCEs or beyond are not suitable.

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Slope Factor

relatively low slopes make housing and road

construction less expensive,

Suitable categoriesslope less than 15%

Unsuitable Categoriesequal to or greater than 15%

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Distance from Water Factor

local groundwater is at risk from septic system

pollution and runoff, environmentalists have pointed

out that

areas further from water bodies and wetlands are

more suitable than those that are nearby.

protected by a 50 meter buffer through constraints.

Suitable categoriesat least 100 meters fromany water body or wetland.

Unsuitable CategoriesWithin 100m of water body or wetland

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IDRISI Steps for Boolean Images

i) Display a Boolean image called LANDBOOL.

j) Display a Boolean image called ROADBOOL.

k) Display a Boolean image called TOWNBOOL.

l) Display a Boolean image called SLOPEBOOL.m) Display a Boolean image called WATERBOOL.

n) Display a Boolean image called DEVELOPBOOL.

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Boolean Aggregation of Factors and

Constraints

all of our factors have been transformed into

Boolean images (i.e., reduced to constraints).

most typical Boolean aggregation procedure.

all eight images are multiplied together toproduce a single image of suitability.

equivalent to a logical AND operation

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In assessing the results of an MCE analysis,

it is very helpful to compare the resultant

image to the original criteria images.

This is most easily accomplished byidentifying the images as parts of a collection

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o)

Open the Display Launcher dialog box and invoke the pick list.

MCEBOOLGROUP in the list with a small plus sign next to it.

This is an image group file that has already been created usingCollection Editor.

Click on the plus sign to see a list of the files that are in the

group. Choose MCEBOOL and press OK.

Note that the file name shown in the Display Launcher input boxis MCEBOOLGROUP.MCEBOOL.

Choose the Qualitative palette and click OK to display

MCEBOOL.

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p)

Use the feature properties query tool (from its

toolbar icon or Composer button) and explore

the MCEBOOLGROUP collection.

Click on the image to check the values in thefinal image and in the eight criterion images.

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Assessing the Boolean Approach

a value of 1 in the final suitability image is only possible whereall eight criteria also have a value of 1,

a value of 0 is the result if even one criterion has a value of 0.

i.e. the suitable places must have the suitability criteria of all thefactors/ constraints. (maximum relationship).

If any one of the factor show unsuitability and all other showsuitable, the location is still unsuitable.

they do not trade off.

In terms of risk, it is very conservative.

no tradeoff and risk aversion

The result is the best location possible for residentialdevelopment and no less suitable locations are

identified.

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MCE:Criter ia Development and

the Boolean Approach

Thanks .

Quest ions / Queries ? ? ?