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Evaluating Techniques for Areal Interpolation of Polygonal Data

Presenter(s):  Erik Glenn

Abstract: 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.

Key Takeaway: Those attending this presentation will learn about the wide variety of techniques for areal interpolation, advantages and disadvantages of each technique, specific software tools (from Esri and others) that perform areal interpolation, and some suggestions for the appropriate tool to use depending on the situation and type of data in question.

Intended Audience: The intended audience includes GIS analysts, natural resources professionals, planners, community development or economic development professionals, and anybody who analyzes data collected within, or aggregated to‚ contiguous polygons.

About the presenter(s):

Erik Glenn is a Senior GIS Analyst with Pima County's Information Technology Department. As a member of its Special Projects team, he works on a variety of geospatial analysis and cartography projects for numerous other County departments. He also administers the County's ArcGIS Online organization, assists with geographic data management tasks, and creates targeted Web applications for some departmental clients. Glenn received an M.S. degree in Geographic Information Systems Technology from the University of Arizona in 2011, and an M.A. degree in Geography from the same institution in 1996. He is also an Esri Certified ArcGIS Desktop Associate.