Crime mapping

Crime mapping plots reported crime incidents by location on a map, using a geographic information system, to make spatial patterns visible that a table of addresses or incident numbers would not show. A basic crime map is simply a dot for every reported incident, often filterable by offense type and date range.

More advanced crime mapping layers in hotspot analysis to test whether visible clusters are statistically significant rather than the product of chance, and can be combined with demographic, land-use, or business-license data to explore possible contributing factors. This differs from predictive policing, which forecasts future incidents; crime mapping is fundamentally descriptive, showing what has already been reported rather than projecting forward.

Police departments use crime maps for daily briefings, patrol deployment, and public transparency, since many agencies now publish interactive crime maps for residents. The main pitfalls are that maps reflect reported, not actual, crime, so they inherit any underreporting or reporting bias present in the underlying data, and that displaying raw incident locations without population normalization can make a densely populated but lower-crime rate area look more dangerous than a sparsely populated one with a genuinely higher rate.