Often, especially when visualizing relationships between multitudes of geographic locations, the traditional map is stretched to its limits. In cases where the exact location is not as important as the legible visualization of relationships or e.g. concurrent attribute visualizations more abstract geographic representations can be a useful tool to overcome some limitations.
One alternative for abstract geographic representations are treemaps. Each Treemap node represents one geographic location or region. While many treemap algorithms use hierarchical visualization algorithms to keep nodes with the same parent node close to each other, geographic treemaps try to maintain the spatial distribution of points and thereby keep the distortion between original geographic position and treemap position as small as possible.
Most existing algorithms take a space-filling treemap approach, e.g. NMAP by Duarte et al  or Jo Wood’s solution . This approach creates two limitations. If the treemap should result in equally sized nodes, the amount of nodes needs to be , otherwise the system needs to fill in blank nodes. As a second constraint the idea of space-filling creates the problem that the actual geographic space might not be close to a rectangle or square.
A major limitation of this approach is, that the whole system is just using the centroids of each region, and especially when looking for empty areas, we don’t take into account that those areas might actually not be empty, but instead large regions. Further more its quite obvious, as the border approach delivers, due to the area-fact, the better results, this approach is limited to datasets, that does not require empty cells to be added in central areas, like e.g. an island dataset.
The code can be found on GitHub.
 Duarte, F.S.L.G.; Sikansi, F.; Fatore, F.M.; Fadel, S.G.; Paulovich, F.V., “Nmap: A Novel Neighborhood Preservation Space-filling Algorithm,” Visualization and Computer Graphics, IEEE Transactions on , vol.20, no.12, pp.2063,2071, Dec. 31 2014; doi: 10.1109/TVCG.2014.2346276
 Eppstein, D.; van Kreveld, M.; Speckmann, B.; Staals, F., “Improved grid map layout by point set matching,” in Visualization Symposium (PacificVis), 2013 IEEE Pacific , vol., no., pp.25-32, Feb. 27 2013-March 1 2013