This hexagonal grid style is an alternative to classic heatmaps. I have applied this method to an OGD dataset of the Viennese tree cadastre containing 119,744 tree positions. The tree counts per hexagonal grid cell reveal some of Vienna’s greenest spots, such as the Prater or Türkenschanzpark.

A description of the workflow can be found at http://underdark.wordpress.com/2012/03/04/mapping-density-with-hexagonal...