Treemaps and Choropleth Maps Applied to Regional Hierarchical Statistical Data

An emerging and challenging Geovisual Analytics application domain is visualization of hierarchical regional (sub-national) statistics. The OECD regional database is a potential treasure chest for policy-makers, researchers and citizens to gain a better understanding of a regionpsilas structure and performance and to carry out analysis of territorial trends and disparities based on sound information comparable across countries. New methods are needed to visually make comparisons between groups on different hierarchical levels, such as cities with countries or parts of countries. In this context, we demonstrate and reflect upon the potential synergy between information and geovisualization through the use of a squarified treemap dynamically linked to a choropleth map to facilitate visualization of complex hierarchical social science data. We exemplify and evaluate our approach with three usage scenarios that explore population change in the OECD countries using 1) squarified treemap, 2) regional choropleth map and 3) combined treemap and choropleth map.