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Lab 10: Suitability Mapping using Fuzzy Logic. Define Goal – Create a Habitat Suitability Map for Nests Define Potential Factors Vegetation Water Roads Determine the Relationship Between Factors and Nests Preprocess Data. Compute Distance from Water and Roads - PowerPoint PPT Presentation
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Lab 10: Suitability Mapping using Fuzzy Logic
• Define Goal – Create a Habitat Suitability Map for Nests • Define Potential Factors
– Vegetation– Water – Roads
• Determine the Relationship Between Factors and Nests• Preprocess Data.
– Compute Distance from Water and Roads– Reclass Distances Into Distance Zones???
• Convert Data to Relative Value – Fuzzy Logic Membership Function (0-1 scoring scheme)
• Combine Factors– Weighted Sum– AND– OR
Advantages of the Fuzzy Logic Approach
• Ability to account for uncertainty
• Relationships can be developed with minimum data
• Relatively simple approach
• Robust, handle missing data, uncertainty
• Easy to interpret and communicate results
• Promote and facilitate user participation
Fuzzy Logic Approach
In classical set theory, membership in a given set is defined aseither true or false (i.e. 1 or 0).
However, membership in a fuzzy set is expressed on a continuousscale from 1 (full membership) to 0 (full non-membership), soindividual measurements of an environmental factor may be defined according to their degree of membership in the set between1 and 0.
Many watershed assessment problems can be viewed as ranking watersheds as either being in the “Very Good Condition” set (1) or “Very Bad Condition set (0), with most of the watershed somewhere in between to two extremes (partial membership).
Landfill Site Selection
Fuzzy membership function related to an environmental factor
Potential range of values
A3
1
xB1 B2Vm
Fuzzy membership function related to an environmental factor
Transformed Fuzzy Scoring Function
A2
A1
0 xB1
FMS
Vo Vx
f(x)
01
f(x)
g(x)
Fuzzy Membership Score:
FMSi = ƒ(Environment Factor Xi) Weighted FMSi = [A1 + ((A3 – A1)/2)] + [A2 – ((A3 – A1)/2) – A1] We will not be doing this step in our Lab.
Composite Fuzzy Score:
nCFS = ∑ (Wi * FMSi) i = 1
Wi = weighting factor for environmental factor i
Other Ways to Combine
• Fuzzy OR (Maximum function) - Increasive• Fuzzy AND (Minimum function) - Decreasive • Fuzzy Product (multiply FMSs) - Decreasive• Fuzzy Sum: CFS = 1 – Π (1 – FMSi) – Increasive
• Gamma: CFS = Fuzzy_sumY * Fuzzy_product1-Y
Lab 9 Results
veg type count frac obs exp x^2
1 9821 0.303117 20 9.093519 13.08089
2 14718 0.454259 9 13.62778 1.57152
3 1922 0.059321 0 1.77963 1.77963
4 1390 0.042901 0 1.287037 1.287037
5 3846 0.118704 1 3.561111 1.841922
6 703 0.021698 0 0.650926 0.650926
sum 32400 1 30 30 20.21193
Vegetation
V = 0.58
Roads
water dist count frac obs exp x^2
1 10135 0.312818 12 9.384549 0.72892
2 9423 0.290842 15 8.725269 4.512439
3 7367 0.227384 3 6.821507 2.140863
4 3891 0.120096 0 3.602889 3.602889
5 1583 0.04886 0 1.465786 1.465786
sum 32399 1 30 30 12.4509
Water
V = 0.46
Model Testing You should perform additional tests to assess model performance.
Chi-square and K-S can be used.Relative indices.If possible use an independent data set for testing.
Model Strength