Police increasingly rely on analysis of crime data, mapping and other methods to develop tactics for addressing specific problems.

Understanding crime data: haunted by the dark figure.

The crime data is mainly from police departments, news reports and user-generated content.

First a user sets the size of the ellipses, typically for a crime data set on a map, miles are used.

The crime data available from the police are for the entire subway system and not for individual lines.

There are two major sources of crime data.

The last year of actual available crime data, as reported above, was 2010.

Each month reported crime data is made available from every police force at an unprecedented level of detail.

There must be analysis of and reaction to crime data on a regular basis.

So despite the impressive crime data, the police department's performance has received mixed reviews in some areas.