Methodology - West Nile Virus Risk Analysis for the City of Burnaby

Methodology

Distance module was used for each of six factors before they can be weighted based on how important the factors are before we can move on to the MCE analysis.

Idrisi Raster files	Distance Module Applied
wetland.rst	wetlanddist.rst
woodarea.rst	woodareadist.rs
parks.rst	parksdist.rst
streets.rst	streetsdist.rst
undevelop.rst	undevelopdist.rst
waterbody.rst	waterbodydist.rst

Weight module then applied to create fuzzy images to determine the importance of each factor to the analysis to where risks would be higher or lower.

Parks Factor: The control points were 300 meters, 1500 meters, 1600 meters and 1700 meters; symmetric, sigmoidal curve was used to rescale the values of the image parksdist so that people living within 300 meters of parks are considered in risk. Suitability increases until it reaches 1500 to 1600 meters away of parks. Then, suitability starts to decline since people are far away from parks and would be able to enjoy less recreational activities. It will also be hard to parents to go to parks with their children to have some family time.

Undeveloped and Open Area Factor: The control points were 300 meters and 2000 meters; monotonically increasing, linear function was used to rescale the values of the image undevelopdist so that people living within 300 meters of undeveloped and open area are considered in risk and increasing suitability until 2000 meters. Beyond 2000 meters, the risk level is the same.

Wetland Factor: The control points were 600 meters and 2500 meters; monotonically increasing, sigmoidal curve was used to rescale the values of the image wetlanddist so that people living within 600 meters of wetland are in risk and suitability increases until it reaches 2500 meters. Beyond 2500 meters, the risk level is the same.

Water body Factor: The control points were 250 meters and 1500 meteres; monotonically increasing, sigmoidal curve was used to rescale the values of the image waterbodydist so that people living within 250 meters of lakes and so on are considered to be in risk. The suitability would increase until it reached 1500 meters when the suitability would be the same for any farther distance.

Wood Area Factor: The control points were 500 meters and 2000 meters; monotonically increasing, sigmoidal curve was used to rescale the values of the image woodareadist so that people living within 500 meters of woodland are considered to be in risk. The suitability would increase until it reached 2000 metes where the suitability would be the same if people live any farther.

Streets Factor: The control points were 0 meters to 50 meters; monotonically increasing, linear function was used to rescale the values of the image streetsdist. This image is used to serve to show that area with heavy “machine” movement and are paved with cement would not likely to generate any suitable breeding grounds for mosquitoes and habitats for birds.

Six fuzz images were then created.

Idrisi Raster files	Weight Module Applied
wetland.rst	wetlandfuzz.rst
woodarea.rst	woodareafuzz.rst
parks.rst	parksfuzz.rst
streets.rst	streetsfuzz.rst
undevelop.rst	undevelopfuzz.rst
waterbody.rst	waterbodyfuzz.rst

After all, a Cartographic Model is created.

Please carry on to Spatial Analysis section to see the Multiple-criteria Evaluation application.