Cartograms, Self-Organizing Maps, and Magnification Control

This paper presents a simple way to compensate the magnification effect of Self-Organizing Maps (SOM) when creating cartograms using CartoSOM. It starts with a brief explanation of what a cartogram is, how it can be used, and what sort of metrics can be used to assess its quality. The methodology for creating a cartogram with a SOM is then presented together with an explanation of how the magnification effect can be compensated in this case by pre-processing the data. Examples of cartograms produced with this method are given, concluding that Self-Organizing Maps can be used to produce high quality cartograms, even using only standard software implementations of SOM.