Mapping Crime: Principle and Practice (Chapter 1)

Crime mapping has long been an integral part of the process known today as crime analysis. The New York City Police Department, for example, has traced the use of maps back to at least 1900. The traditional crime map was a jumbo representation of a jurisdiction with pins stuck in it (figure 1.1). The old pin maps were useful for showing where crimes occurred, but they had serious limitations. As they were updated, the prior crime patterns were lost. While raw data could be archived, maps could not, except perhaps by photographing them. 1 The maps were static; they could not be manipulated or queried. For example, it would have been difficult to track a series of robberies that might overlap the duration (a week or month) of a pin map. Also, pin maps could be quite difficult to read when several types of crime, usually represented by pins of different colors, were mixed together. Pin maps occupied considerable wall space; Canter (1997) noted that to make a single wall map of the 610 square miles of Baltimore County, 12 maps had to be joined, covering 70 square feet. Thus pin maps had limited value—they could be used effectively but only for a short time. However, pin maps are sometimes still used today because their large scales allow patterns to be seen over an entire jurisdiction in detail.