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Spring 2003
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Chester, Pennsylvania, Police Use GIS to Identify "Hot Spots"

By Garnet R. Daus and Kevin Switala, GeoDecisions

According to the Federal Bureau of Investigation's Uniform Crime Reports (UCR), the nationwide crime index decreased for the ninth straight year in 2000, declining 3.3 percent from 1999. The UCR program collects information from local law enforcement agencies about crimes reported to police and includes homicide, forcible rape, robbery, aggravated assault, burglary, larceny, and motor vehicle theft.

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The prototype animation tool generates a short movie of changing densities of a particular type of crime over a period of time defined by the user.

Although the national trend in crime is down, the Chester Police Department (CPD) wasn't satisfied with its crime-fighting measures. The only city located in Delaware County, Pennsylvania, Chester had a history of high, concentrated crime.

"We wanted to identify the hot spots and strategize to reduce crime," says Cyrise Dixon, the crime mapping coordinator for CPD.

Prior to July 2000, the CPD used a pin map system. Using a paper map, law enforcement personnel would literally use a pin to mark the location of a crime in an effort to observe activity.

"Up until three years ago, this was a paper and pencil shop," Dixon adds. "Technologically, that wasn't helping us. You can't query or compare time periods with this type of system."

Frustrated with this fact, Dixon set out to learn more about how computer technology, and specifically GIS, could help her analyze information more effectively. After seeing ArcView demonstrated at various conferences and taking an Esri-sponsored ArcView class, she was able to see just how effective ArcView could be at querying incident data, determining crime patterns, and displaying complex spatial information.

With a $110,000 grant from the Pennsylvania Commission on Crime and Delinquency in 2000, the CPD was finally able to take a more modern approach to its crime-fighting practices.

Before awarding the project, the city of Chester advertised locally and solicited responses from qualified consulting firms. From this group, the CPD selected Esri Business Partner GeoDecisions, which immediately began implementing its GeoDecisions Crime Analysis and Mapping System, or GeoCAMS, a desktop application that provides various analytical and deployment tools to law enforcement staff.


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The detective information mapping tool allows investigators to record and visually represent the networks of locations comprising a suspect's activity space.

Chester's version of GeoCAMS is known as the Chester Crime Analysis and Mapping System (CCAMS). It enables CPD law enforcement personnel to search for, map, and analyze incident and intelligence data as well as generate deployment plans.

CCAMS consists of three spatial components. The first allows a user to see what happened as well as where and when a crime took place. The second enables users to create a tactical deployment plan by drawing on a map and alerting law enforcement personnel close to the scene. The third component, the detective information mapping tool, gives users the opportunity to create a map that records the physical, social, and location-based characteristics of a suspect. This spatial web of activity shows where a suspect lives and works as well as the places he/she frequents. All of this information can be queried.

CCAMS is the first application of its kind to build spatial and temporal webs of information for use in law enforcement.

CCAMS Stages

CCAMS was introduced in several stages. First, a thorough needs assessment was conducted to gather information on existing operational procedures, hardware and software, crime data, and personnel needs. During the needs assessment process, various members of the CPD were shown technology and analysis techniques using Esri development tools and applications. The accessible methods, flexible development environment, and clear graphics provided by ArcView and MapObjects technology were immediately attractive to CPD for use in the city's crime mapping system.

The second stage involved developing a law enforcement specific spatial data set or basemap, composed of specific layers, such as the location of city streets, schools, railroads, and hospitals, that would eventually serve as context on future incident maps. Parcel data was obtained from the county. From this information, park, school, hospital, and other parcel-based data was derived utilizing ArcView. The street centerline needed for geocoding was obtained for a modest amount from Geographic Data Technology, a geospatial data vendor. CPD personnel then drove throughout the city to verify and correct the address ranges. Other contextual and emergency management data was collected from the Pennsylvania Spatial Data Access, a geospatial data portal run through The Pennsylvania State University.

In the third stage, an automated law enforcement report tracking system was integrated with GIS. This function enables law enforcement personnel to enter incident queries, locate crime scenes on a map, and generate police reports that contain information about the crime and suspects. Esri development technology makes the system so easy to use that police officers with only limited computer experience can operate it. This step also involved the implementation of the detective information mapping tool.

The fourth and fifth stages involved system distribution and training. The crime database uses Microsoft Access residing on a Dell Server, while the MapObjects/Visual Basic-based CCAMS application was loaded locally on four Dell Pentium II workstations available to CPD personnel. Upgrading these workstations and available color printers is a continuous process.

For more information about CCAMS, contact Cyrise Dixon (tel.: 610-447-8437, e-mail:, Web: or Kevin Switala (tel.: 215-557-0106, e-mail:, Web:

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