Calculates the circularity of an area feature, which indicates how elongated the feature is. A value of 1 indicates that the feature is a perfect circle, and 0 indicates that it is a line. This will help you find elongated features.
The attached workspace (See attachment: CircularityCalculatorExample.fmw) calculates the circularity of political boundaries within Canada. The theory is that citizens are better represented when they live in a more circular political riding. That's because they have more equal access to their elected representative, plus the representative has equal access to any area of the riding.
The source data is a set of federal riding boundaries for Canada. It is not included here but can be obtained from Natural Resources Canada's GeoGratis web site at http://www.geogratis.gc.ca/download/electoral/2008/fed308.2008.zip (ESRI Shape format - not that this matters to an FME user!)
The workspace to carry out this process is very simple:
The output (as shown in the FME Universal Viewer) looks like this.....
The above was calculated using the convex hull of each feature to calculate circularity. If you use the actual polygon shape then the most and least circular are Langley and Labrador.
Determine how circular or long (elongated) an area is based on its convex hull or boundary
Article Number: 000001405 - Last Modified: Jan 25, 2012
The CircularityCalculator calculates the circularity of an area feature, which indicates how elongated the feature is.