Heat Mapping Crime Data with Bing Maps and HTML5 Canvas. Crime data is frequently presented using “heat maps”.
See, for example: One of the reasons why heat maps are used to visualise crime data is that crimes are typically recorded as individual incidents, occurring at one particular location, yet we tend to want to think of areas at high- or low- risk of crime. We therefore need some way of aggregating those individual crime occurrences into regions that can be analysed. It doesn’t necessarily make sense to create a thematic map of crimes based on geographic or administrative divisions – a burglar probably does not have much regard for whether he commits a crime in one polling district/ward/street of a city or another, for example, and we should not attempt to fit the distribution of crimes to such arbitrary regions. Node.js + Express + Leaflet + PostGIS = Awesome Maps. Recently I blogged about using GeoJSON to create a very lean application for serving dynamic maps.