<http://schema.org/image>
<http://static1.squarespace.com/static/5273d1fce4b06060b5e45101/t/54ceaa1de4b03a59e1143a05/1463683913431/>
<http://www.delimited.io/blog/2013/12/1/hexbins-with-d3-and-leaflet-maps>