M6 - Post 1 - Suitability Analysis

 This is the first part of a two post final module for GIS 5100, Applications in GIS. 

This last module combines many of the skills that have been acquired, strengthened, and challenged during this course. Specifically, we are working through a significant amount of raster data manipulation to generate a suitability analysis. Under the auspices of being a budding GIS analyst for a property developer, my task was to take five factors, transform data relating to them, and generate a weighted overlay, to provide a suitability assessment for the subject area. 

The subject categories are: Land Cover, Soil Type, Slopes, Streams, and Roads. 

Land Cover was already in raster format, but required reclassification to provide favorable weight to agricultural areas and meadow or grasslands. 

The Soil analysis having previously been completed was a polygon layer requiring conversion to raster, and then adjusting the suitability for arability. 

A DEM was provided so that I could transform it into a Slope raster, and then heavily weight mild slopes. 

For streams, while water is a desirable feature, it was weighted by distance away from it. 

Roadways are key for accessibility and as such heavily weighted based on distance from a roadway out to 1 mile. 

All of these datasets varying factors were given a value of 1 - 5, with 1 being least suitable and 5 being most suitable. This means, that each raster Cell was provided a value on this scale based on the real factor its source raster represented. Then the weighted overlay tool provides a composite score by cell, and based on the weight applied to each factor. 

In the case of the map comparison below, the left pane has all of the five factors being weighted equally. The right pane provides a variable weight as depicted. 

The biggest takeaway is that by weighting the factors differently you can vastly change the amount of suitable or unsuitable area that you are working with. Also remember that the suitability factors created by the Weighted Overlay process must end up in a whole integer. Normal rounding rules apply for each cells value. A cell weighted at 4.29 and 3.75 will both end up being a 4. etc. 

Now stay tuned for part 2 coming up next.