Reading a Crime Map

Maps of hot spots areas convey powerful messages to their readers. These messages are conveyed by various symbols:

Points

  • Points (or dots) draw attention to specific places and suggest that places with many points have local problems unique to that location. A point conveys the message that the hot spot is located at this exact location and should be the focus of police efforts.

Street segment

  • A shaded street segment suggests that the chances of crime are roughly equal along the entire segment and police efforts should focus along this segment but not along other streets.

Shaded area

  • A shaded area, which shows discrete distributions of crime for particular areas such as beats, precincts, districts, counties, or census blocks, also suggests equivalent risks of crime throughout the area with a dramatic reduction in risk at the border. It suggests that police activity throughout the area is appropriate.

Density surface

  • A density surface, which depicts crime estimates of frequency or risk as a surface of color gradients that imply a high level of crime activity in its center which gradually tapers off in the outer areas. It directs police attention to the center and its surroundings.

Each way of depicting hot spots is connected with useful theories on why crimes occur in hot spots, each of which suggests different types of police action. Recognition of these links in mapping practice can lead to better use of crime maps.

See chapter 1 of Mapping Crime: Principles and Practice for more on how to read and understand crime maps.

Date Created: October 9, 2009