Heat maps /Density Maps
Heat map icon type is listed inside of the icon style property. This visualization displays density of latitude and longitude points on a map. As the number of data points increase in a specific area, the color intensity will increase. The heat map icon style currently includes pre-defined fill types that can be layered across multiple series. Like icons, heat maps can use dynamic icon sizing.
Heat map/Density Map Style
Heat map data points, can contain an additional measure, heat map intensity data, to control the color intensity of each data point. Like labels and values, binding heat map intensity data will require one cell per data point.
– See more at: http://cmapsconnect.com/tutorial/icon-color/#sthash.JybGVoHD.dpuf