Crime Mapping (continued)

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CRIME MAPPING (continued)

Creating Maps

Crime mapping has its roots in cartography⁸ and comes with its own set of rules and limitations. When publishing an article, authors always cite information resources. When constructing a map, cartographers always cite the source of the data and the software used to create the map. If citations are left out, the map is incomplete and users may misinterpret the information displayed. It is also recommended that mapmakers include disclaimers and/or additional information to eliminate any misinterpretation of the material. A variety of maps can be created using GIS software, but the three most common are pin maps, thematic maps, and association or integrated maps.

Pin Maps

Questions To Consider (Exhibit 5)

One of the unique qualities of GIS is that it creates new information and stimulates questions. For instance, some questions that could be generated from the Washington, D.C., pin map include

Were the number of applications for crime victim compensation consistent with the number of homicides that occurred in the area?
Are services available to the survivors of homicide victims?
Where are services located?

Pin maps—which use push pins to identify important locations—have long helped police officers patrol neighborhoods and detectives investigate crimes. GIS enables law enforcement agencies to create, update, duplicate, and distribute pin maps more efficiently and easily. Administrators of VOCA victim assistance can plot the locations of victim service providers on pin maps to identify gaps in and duplication of services. Victim service providers can display the vicinity of crime victims to better coordinate their efforts with other providers. The pin map is one of the easiest maps to create. Exhibit 5 shows the locations of all homicides that occurred in Washington, D.C., in 1994 and 1995. During the 2-year period, there were 756 murders and all but one occurred east of the Rock Creek Park.⁹ Although the points on the map only show location, they reveal a spatial significance that cannot be discerned using a tabular query.

Thematic Maps

Questions To Consider (Exhibit 6)

Is the density of subgrantees consistent with population?
Is the density of subgrantees consistent with the crime rate?
What types of services are provided in all counties?
Where are the gaps?

A thematic map can identify the density value of a particular attribute, such as the number of assaults, crime victim service centers, or victim compensation claims in a geographically defined boundary composed of a state, police precinct, county, neighborhood, census tract, or victim service provider catchment area (see exhibit 10). In exhibit 6, density values are used to create a map, with shaded colors representing the different values between the boundaries, that allows users to examine patterns across selected boundaries. The shading of thematic maps ranges from light to dark, with the lightest shade representing the lowest value and the darkest shade representing the highest value. Exhibit 6 shows the density of California VOCA subgrantees by county.

Association or Integrated Maps

Questions To Consider (Exhibit 7)

Are a sufficient number of claims being
generated based on this assault data?
Where are hospital emergency rooms
located?
Are admission staff trained in
compensation?
Is there a victim advocate in the police
department in areas with higher
assault rates?
Are other state and federal resources,
in addition to victim compensation and
assistance, being integrated in the
public housing communities?

In 1998, the U.S. Department of Justice launched the Strategic Approaches to Community Safety Initiative, a multiagency collaborative approach to reduce crime in communities by using data-driven problem solving. One major component of this project has been the development of the Community Safety Information System (CSIS), a GIS that provides spatial analysis capabilities for addressing crime. Exhibit 7 is an integrated map created from CSIS data collected in Winston-Salem, North Carolina, the pilot site for the initiative.

Association or integrated maps are usually a combination of a pin map and a thematic map. Exhibit 7 combines data from North Carolina’s Winston-Salem Police Department (WSPD), the Winston-Salem Housing Department, and the U.S. Census Bureau. In this map, aggravated assaults and public housing units are identified with points, while the population demographics are represented with various shades of the same color and organized by police district boundaries.

This map spatially contextualizes¹⁰ the data. Here, WSPD chose to view census data reaggregated to police beat boundaries. With this type of map, WSPD can view income, population, gender, race, and other factors within the boundaries that represent the department’s work environment. Winston-Salem manages and allocates police department resources by police districts. By reaggregating census data, information has been made more applicable to department needs. For instance, WSPD may choose to increase resources in communities with large numbers of public housing units. Integrated crime mapping allows WSPD to make strategic administrative decisions based on contextualized data.

Contents


Using Geographic Information Systems To Map Crime Victim Services: A Guide for State Victims of Crime Act Administrators and Victim Service Providers	February 2003

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