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 mapswhich use push pins to identify important locationshave
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.
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
- Were the number of applications for crime victim compensation
consistent with the number of homicides that occurred in
- Are services available to the survivors of homicide victims?
- Where are services located?
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.
To Consider (Exhibit 6)
- Is the density of subgrantees consistent with population?
- Is the density of subgrantees consistent with the crime
- What types of services are provided in all counties?
- Where are the gaps?
Association or Integrated Maps
Association or integrated maps are usually a combination of a pin map and
a thematic map. Exhibit
7 combines data from North Carolinas 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.
To Consider (Exhibit
- Are a sufficient number of claims being
generated based on this assault data?
- Where are hospital emergency rooms
- Are admission staff trained in
- Is there a victim advocate in the police
department in areas with higher
- 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.
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 departments 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.
|Using Geographic Information Systems To Map Crime
A Guide for State Victims of Crime Act Administrators and Victim Service