Weighted Overlay
Weighted overlay analysis is important in analyzing problems based on multiple criteria. This technique applies a common ‘weight’; measurement scale of values usually set by the user; to different criteria factors being considered. This would yield a raster image showing the suitable factors based on the measurement scale of values set by the user.
In this exercise, the weighted overlay function was used to determine the most suitable areas for bear locations in the Great Smoky Mountains. The criteria used to determine these areas were distance from roads, streams, trails within vegetation and slope. The favorable, unfavorable and most favorable values are shown in the table below.
click to enlarge
A model builder was used to run all the tools used in this analysis.
Description of Procedure;
The first analysis procedure used was to determine the distances of the road, streams and trails factors. This was done using the Euclidean Distance tool in the model builder; this was used to calculate the distance for each raster cell to the closest source (streams, roads or trails). The resulting distances were in raster formats.
Model showing the analysis procedure(click to enlarge)
The Slope tool was used to identify the rate of change from each cell of the raster surface.
The Reclassify tool was used to set the values of all the resulting raster images using the measurement values shown above. These images were used as the input raster. Using a scale value of 1 to 3 where 3 was used to represent the most favorable factors. What this method basically does is assign set values (in this case, 1, 2, and 3) to each raster cell.
Table showing reclassification of one of the factors; Roads.(click to enlarge)
The final analysis procedure was to overlay the 5 rasters, after reclassifying, using a common measurement scale (1 to 3 by 1), and weighs each rasters according to its importance (equal importance of 20%). This was done using the Weighted Overlay tool. This results in the display of favorable, most favorable and least favorable locations for bears in Smoky Mountains.
Weighted Overlay Analysis(click to enlarge)
Map showing suitable areas for bear habitats(click to enlarge)
Applications and Reflections;
I can use the weighted overlay analysis in finding a suitable home for myself or family. Using different factors such as home value, size, type, proximity to public amenities or recreation areas, values can be set. This would result in suitable home locations based on my set factors.