Evaluating Techniques for Areal Interpolation of Polygonal Data
Many GIS professionals have been tasked with taking one polygonal dataset and attempting to convert it into another set of polygons, e.g. taking Census data collected by tract or block group and assigning it to Zip Codes. This process of assigning attributes from one set of polygons to another set of polygons with different sizes and shapes is called areal interpolation. The so-called "area-proportion" method is one of the simplest ways to do this. Unfortunately, our data almost never change predictably across our polygons, much less exhibit a uniform distribution. We know that aggregating or grouping data will inevitably cause bias depending upon the zones or districts used. This is true no matter which areal interpolation technique we use. However, there are many ways to substantially improve the quality of this process. Come to this session to learn about additional areal interpolation methods, the pros and cons of using them, and specific areal interpolation software tools.