UNIT 3
Module 11
Crime Mapping
Introduction to Crime Mapping
Ever since maps have been available that depict the geographic features of
communities, such as streets and city boundaries, police departments have used
such maps to determine patrol areas and emergency routes as well as to assist
patrol officers in finding specific addresses. Police departments have also
mapped crime, a process that, until recently, involved the manual placement of
pins on hand-drawn wall maps. This chapter discusses the emergence of
computerized crime mapping as a tool for conducting crime analysis. It begins
with an introduction to key terms and then describes basic concepts before
presenting a history of crime mapping and information on the field’s current
status and career paths.
Crime mapping is a geographical representation of crime data to identify patterns,
trends, and hotspots in specific areas. This technique involves the use of Geographic
Information System (GIS) technology to visualize and analyze crime-related information
on maps. Crime mapping can provide valuable insights for law enforcement agencies,
policymakers, and the public in understanding the spatial distribution of crime (spatial
refers to the location or position of events in physical space).
Definitions: GIS and Crime Mapping
A geographic information system (GIS) is a powerful software tool that allows the
user to create any kind of geographic representation, from a simple point map to
a three-dimensional visualization of spatial or temporal data. For the purposes of
this book, the definition of a GIS is as follows:
A GIS is a set of computer-based tools that allows the user to modify,
visualize, query, and analyze geographic and tabular data.
Crime mapping is the process of using a geographic information system
to conduct spatial analysis of crime problems and other police-related
issues.
Clarifying where different types of crime and other incidents occur is one
of the many important functions of crime analysis. Because of the
unique nature of the software used and the prominence of geographic
data in crime mapping, this type of analysis is often discussed as though
it is distinct from crime analysis; in reality, however, crime mapping is a
subdiscipline of crime analysis. Crime mapping serves three main
functions within crime analysis:
1.It facilitates visual and statistical analyses of the spatial nature
of crime and other types of events.
2.It allows analysts to link unlike data sources together based on
common geographic variables (e.g., linking census information,
school information, and crime data for a common area).
3.It provides maps that help to communicate analysis results.
Crime analysis is a systematic process of collecting, categorizing, analyzing,
and interpreting crime data to provide valuable information and support
decision-making in law enforcement and public safety. The goal of crime
analysis is to identify patterns, trends, and insights that can assist law
enforcement agencies in preventing and solving crimes, as well as improving
overall public safety.
Crime mapping is complementary to all forms of crime analysis in that it
plays an important part in almost every analysis. As Figure 4.1 illustrates,
crime mapping does not stand alone; rather, it is a process that occurs
within the larger process of crime analysis. The following are some
examples of how crime mapping is used within the three types of crime
analysis:
In tactical crime analysis, crime mapping is used to identify
immediate patterns for crimes such as residential and commercial
burglary, auto theft, and theft from vehicles. For example, spatial
analysis of auto theft incidents may reveal clusters of activity at
specific locations that might indicate a crime pattern.
Tactical crime analysis is a specific branch of crime analysis
that focuses on providing timely and relevant information to
support the immediate needs of law enforcement operations and
investigations. Unlike strategic or long-term crime analysis,
which looks at broader trends and patterns, tactical crime analysis
is geared toward addressing immediate and specific issues faced
by law enforcement officers on the ground.
Ex. (Tactical)
A neighborhood has experienced a surge in residential robbery
over the past few weeks. The local law enforcement agency
wants to address this issue promptly and efficiently. A tactical
crime analyst is assigned to provide support to officers on the
ground.
Ex. (Strategic) A city has experienced an increase in property
crimes, including burglaries, auto thefts, and vandalism. The city's
law enforcement agency wants to develop a long-term strategy to
address these issues systematically. A strategic crime analyst is
assigned to assess the overall crime situation and provide
insights for a comprehensive, city-wide approach.
In strategic crime analysis, crime mapping is utilized in long-
term applications to analyze the relationship between criminal
activity and indicators of disorder, such as a high volume of
vacant property or disorder calls for service; to assist in
geographic and temporal allocation of resources, such as patrol
officer scheduling and determination of patrol areas; to examine
patterns of crime at or around specific locations, such as schools,
bars, or drug treatment centers; to calculate crime rate
information, such as numbers of residential burglaries per
household; and to incorporate crime data with qualitative
geographic information, such as information on teenage
hangouts, student pathways to school, or drug and prostitution
markets.
In administrative crime analysis, crime mapping is a valuable
tool used by police, researchers, and media organizations to
convey criminal activity information to the public. Web sites
operated by police departments and news organization routinely
post maps that depict areas of crime, along with corresponding
tables and definitions. For example, a police agency can reduce
citizen requests for neighborhood crime information by placing
monthly or weekly crime maps on a Web site that members of the
public can access using computers in their homes or at the local
library.
Administrative crime analysis focuses on providing information
and support for the administrative functions of law enforcement
agencies. Unlike tactical or strategic crime analysis, which
primarily assist with operational decision-making and long-term
planning, administrative crime analysis deals with internal
processes, resource allocation, and organizational efficiency.
Ex. A police department wants to improve its overall efficiency
and resource allocation to better serve the community. An
administrative crime analyst is tasked with evaluating various
internal aspects of the department's operations.
Geographic Features
A geographic information system translates physical elements in the real world— such
as roads, buildings, lakes, and mountains—into forms that can be displayed,
manipulated, and analyzed along with police information such as crime, arrest, and
traffic accident data. A GIS uses four types of features to represent objects and
locations in the real world; these are referred to as point, line, polygon, and image
features (for a discussion of the attribute data behind these features, see Chapter 6).
Point Features
In crime mapping, point features represent specific locations where individual crime
incidents have occurred. Each point on the map corresponds to the geographical
coordinates (latitude and longitude) of a particular crime event. A point feature is a
discrete location that is usually depicted on a GIS-generated map by a symbol or label. A
point feature is analogous to a pin placed on a paper wall map. A GIS uses different
symbols to depict the locations of data relevant to the analysis, such as crimes, motor
vehicle accidents, traffic signs, buildings, police beat stations, and cell phone towers.
Line Features
A line feature is a real-world element that can be represented on a map
by a line or set of lines. Other types of line features include rivers,
streams, power lines, and bus routes.
Polygon Features
A polygon feature is a geographic area represented on a map by a
multisided figure with a closed set of lines. Polygons can represent areas
as large as continents or as small as buildings; in GISgenerated maps
they may be used to depict county boundaries, city boundaries, parks,
school campuses, or police districts.
Image Features
An image feature on a GIS-generated map is a vertical photograph taken
from a satellite or an airplane that is digitized and placed within the
appropriate coordinates. Such photos, which may appear in black and
white or color, show the details of streets, buildings, parking lots, and
environmental features (landscaping).
Module 12
Types of Crime Mapping
Several types of mapping are used routinely in crime analysis. This section provides a
brief introduction to the various types of crime mapping to set the stage for the chapters
that follow, which discuss the creation of maps and their application to crime analysis in
more detail.
Single-Symbol Mapping - Single-symbol mapping is a cartographic technique
used in geographic information systems (GIS) and mapping to represent a
single category or type of data with a consistent symbol or color. In the context
of crime mapping or any other thematic mapping, it involves using a uniform
symbol to represent all instances of a particular phenomenon, such as a
specific type of crime or a particular attribute.
In single-symbol maps, individual, uniform symbols represent features
such as the locations of stores, roads, or states. An important thing to
keep in mind about single-symbol maps is that a GIS places all points on
such a map that share the same address directly on top of one another,
making it impossible for the map to show how many points there really
are. Because of this, crime analysts use single-symbol mapping primarily
to display geographic information in which there is no overlap; they
employ other types of maps to convey information about multiple
incidents at particular locations. In addition, single-symbol maps are not
useful when analysts are dealing with large amounts of data. Thus
analysts use single-symbol maps primarily when they are working with
relatively small amounts of data that do not overlap. Police agencies also
often use single-symbol maps to communicate the locations of crimes
within patterns to police personnel.
Buffers - A buffer, in the context of geographic information systems (GIS) and
mapping, is a zone or area surrounding a feature (such as a point, line, or
polygon) within a specified distance or proximity. Buffers are commonly used
in spatial analysis to assess and visualize the spatial relationships between
different geographic features.
A buffer is a specified area around a feature on a map. Buffers can be set
at small distances, such as 50 feet, or larger distances, such as 500
miles, depending on the purpose and scale of the map. Buffers help in
crime analysis by illustrating the relative distances between features on a
map. Buffers can also be used as polygons for data aggregation and
comparison.
Graduated Mapping - Graduated mapping, also known as graduated symbol
mapping, is a cartographic technique used in geographic information systems
(GIS) to represent variations in the magnitude or quantity of a specific attribute
across different locations. This technique involves using symbols of varying
sizes, colors, or shapes to visually convey the differences in the values of the
chosen attribute. Graduated mapping is particularly useful when you want to
emphasize the relative differences in magnitude between features.
Crime analysts often use graduated maps—that is, maps in which
different sizes or colors of features represent particular values of
variables. In a graduated size map, the sizes of the symbols used for
point and line features reflect their value. As noted above, single-symbol
maps are not appropriate for displaying data about crimes that occur at
the same locations repeatedly. Analysts use graduated size maps for this
purpose, because these maps can account for multiple incidents at the
same locations. However, like single-symbol maps, graduated size maps
are subject to overlapping points if too many data are analyzed at once.
In a graduated color map, the colors of the symbols reflect their values;
this kind of mapping can be used with points (in a single-symbol map
only),2 lines, and polygons.
Chart Mapping
Chart mapping allows the crime analyst to display several values within a
particular variable at the same time (e.g., variable = crime, values =
robbery, assault, and rape). There are two types of chart mapping: pie
and bar. In pie chart mapping, the relative percentages (represented by
slices of a pie) of values within a variable are displayed.
Density Mapping
In density mapping, analysts use point data to shade surfaces that are
not limited to area boundaries (as is the case in graduated color
mapping). In their most basic form, density maps are shaded according
to the concentration of incidents in particular areas.
Interactive Crime Mapping
Rather than a type of mapping, the term interactive crime mapping refers
to simplified geographic information systems made available to novice
users over the Internet. Many police departments have interactive Web
sites where citizens and police officers can conduct basic crime mapping
themselves. These applications typically are not flexible or sophisticated
enough to be useful to crime analysts.
Module 13
History of Crime Mapping
Even though crime mapping plays a significant role in crime analysis today, conducting
spatial analysis and creating crime maps have only recently become common in policing
and crime analysis, thanks to advancements in technology. Unlike crime analysis, the
history of crime mapping begins not with the establishment of the first police force, but
with researchers long before computers were invented.
Beginnings of Crime Mapping
In the 1800s, European researchers who adhered to the school of thought
known as the cartographic school of criminology examined the levels of crime
within different areas (regions) and the relationship of these levels to sociological
factors, such as socioeconomic status (Groff & La Vigne, 2002). For example, in
1829, Adriano Balbi, an ethnographer and geographer, and André-Michel
Guerry, a lawyer, created the first maps of crime using criminal statistics for the
years 1825 to 1827 and demographic data from the census. They examined
crimes against property, crimes against persons, and levels of education in
France and found that areas with high levels of crimes against property had a
low incidence of crimes against people and that higher numbers of educated
people lived in areas with more property crime (Weisburd & McEwen, 1997).
Also during this period, the Belgian astronomer and statistician Quételet used
maps to examine correlations between crime and transportation routes,
education levels, and ethnic and cultural variations (Weisburd & McEwen, 1997).
United States: 1900–1970
In the United States, the use of crime mapping began a little later than it did in
Europe. Because the United States was a relatively new country in the 1800s,
reliable maps were not readily available and census data were not regularly
collected, as they were in France and England at that time. The first substantive
spatial analysis of crime in the United States was conducted in the 1920s and
1930s by urban sociologists in Chicago. Their crime research and related crime
maps linked crime and delinquency to factors such as social disorganization and
poverty. In fact, these scholars’ spatial analysis of juvenile delinquency and
social conditions in Chicago is considered to be one of the foremost examples of
crime mapping in the first half of the 20th century (Groff & La Vigne, 2002).
Crime mapping was a theoretical component in the development of the
concentric zone model, which contends that in an urban setting different types of
zones (areas with different purposes) form around a central business district and
that some of these zones are more prone to crime and disorder than are others.
Researchers who analyzed the locations and distribution of gangs in Chicago
based on the concentric zone concept found that gangs were concentrated in
parts of the city where social control was weak and social disorganization was
high (Weisburd & McEwen, 1997). Most of the early crime mapping conducted in
both Europe and the United States examined aggregate levels of crime by area.
However, evidence exists of a map that was created by hand in 1929 by
Chicago school researchers in which the home addresses of more than 9,000
delinquents were clustered in particular areas of Chicago (Weisburd & McEwen,
1997).
Through the 1950s, 1960s, and 1970s, sociologists and others who were
interested in crime and its causes continued to examine the sociological factors
associated with crime. The explanations and geographic methods of analysis
used remained fairly uncomplicated during this period, possibly owing to the
researchers’ focus on sociological factors and the lack of adequate technology
(Groff & La Vigne, 2002). In the late 1960s, scholars began conducting spatial
analysis of crime with the help of large computer systems and unsophisticated
visualization methods (Weisburd & McEwen, 1997).
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