Alison Hayes November 30, 2005 NRS 509. Crime Mapping OVERVIEW

Transcription

1 Alison Hayes November 30, 2005 NRS 509 Crime Mapping OVERVIEW Geographic data has been important to law enforcement since the beginning of local policing in the nineteenth century. The New York City Police Department was using pin maps as early as the 1880 s. This method was labor-intensive, had limited capacity, and was unable to accommodate archiving. The arrival of GIS in the field of law enforcement has eliminated these obstacles and has enabled criminal justice professionals to explore questions of spatial criminology in greater detail than ever before. The first decade of widespread GIS applications in law enforcement was roughly between 1985 and Today, GIS is being utilized for law enforcement purposes in countless ways. Uses of crime mapping include informing officers of local crime patterns, resource allocation decisions, evaluation analysis and even crime forecasting and geographic profiling of ongoing crime series. Specifically, GIS is currently being utilized to: pinpoint killers, analyze traffic accidents, track parolees and registered sex offenders, and conduct robbery analyses. In addition, GIS combined with GPS has been successful in locating missing persons. The movement away from traditional centralized police operations towards a more intelligence-led proactive style of policing has contributed to the increased use of crime mapping. Intelligence-led policing involves the systematic analysis of crime data in order to target existing and emerging crime problems more effectively. Crime hot spots are becoming central to policing strategy in many locations, as they enable police departments to focus resources into areas of greatest need. Hot spots are areas of high concentration of crime. Crime data is analyzed to determine hot spots and problem solving techniques are then applied in order to reduce crime at specific locations. Mapping crime hotspots has been applied to general crime analysis, vehicle crime analysis, serial criminal investigations and gang activity. Using intelligence from reviewing hotspot maps helps a police department allocate its officers in the most efficient manner. There are a number of GIS-based software programs on the market today that are specifically designed to assist police departments in tracking crimes more efficiently and improving their ability to follow crime trends. For example, ComStat, short for computer comparison statistics, was developed in New York City and helped to drastically lower the city s crime rates. ComStat allows police officers to look at maps of criminal activity and compare them with response rates and effectiveness. This program is now being employed by numerous police departments across the country including Baltimore and New Orleans. The source of much of the raw data for crime mapping and studies is from local police department databases. Such internal data sources may include: calls for service,

2 arrests, traffic accidents, sex offender registrants, and citations. Those external to the police department may find it difficult to obtain these sources of micro-level crime data. Obtaining supplemental data from sources outside the police department is essential to crime analysis and mapping. Geographic data such as roads, property parcels, bus stops, school locations, and recreational areas are frequently represented layers on crime maps that are often available through local government agencies. Aerial photography and census data are also commonly used as supplemental data in crime mapping. Other sources for crime data include Uniform Crime Reports (UCR) and the National Incident Based Reporting System (NIBRS). The data from these sources are aggregated to the municipal level and the number of crime incidents is provided for a particular location such as state, county, or municipality. Therefore, these sources are limited in their application. The future of GIS in crime prevention is going beyond simple data analysis and using statistical regression and other means for more complex analysis, such as criminal behavior modeling. As more police departments make crime maps available on their websites, crime mapping will continue to play an important role as an effective means of communication not only within the police department but also within the community. GIS has been embraced by law enforcement professionals for conducting day-to-day operations as well as for planning, analysis and decision support. GIS will increasingly become a necessity for law enforcement officials as the benefits of these applications become fully realized. With researchers and practitioners working together, GIS applications in the field of law enforcement is only limited by imagination. ANNONTATED BIBLIOGRAPHY Bowers, Kate J., and Shane D. Johnson Measuring the Geographical Displacement and Diffusion of Benefit Effects of Crime Prevention Activity. Journal of Quantitative Criminology 19:3, The objective of this paper is to develop a tool to assist in the measurement of levels of displacement. The authors advocate for the use of a standardized method that will both promote empirical work on geographic displacement and allow for comparisons of results from different studies. The authors present the weighted displacement quotient and argue it is fairly simple to implement and flexible enough to allow analyses to be conducted using either aggregate or disaggregate data at almost any unit of analysis. A positive aspect of the weighted displacement quotient is that it controls for attribution failure by relating changes in the buffer zone to those in the target area. Before concluding, the authors rightfully discuss a number of methodological issues that should be considered when using this technique. In general, I found the article challenging to follow and that concepts could have been better explained. However, I would still consider it an important article for those in the field who may be more familiar with the concepts and methodology and therefore have more to gain from its insights.

3 Canter, Philip and Keith Harries Police Officers' Perceptions of Maps and Aerial Photographs. International Journal of Police Science & Management 6:1, This study looks at the effectiveness of maps and aerial photographs used in the context of law enforcement. Specifically, the authors attempts to answer the question, What should be the relationship between the area covered by maps and the degree of detail contained in them? In order to answer this question, a sample survey was conducted of police officers in Baltimore, Maryland. The officers were asked to compare alternative visualizations of crime data presented at various scales. In general, representations containing richer detail were preferred over the conventional abstract linear maps. However, any conclusions based on the survey findings should be viewed with caution due to its small sample size of 24. Although the survey results may not be significant, preferences identified by police officers are valuable to consider since they are they are ones who will be utilizing this tool in the real world. Ultimately, and not surprisingly, the research found that the choice of the scale and what is to be displayed depends on the purpose of the map and the personal preference of the user. The article also provides a nice background on the use of GIS for law enforcement purposes. Craglia, Massimo, Robert Haining, and Paul Wiles A Comparative Evaluation of Approaches to Urban Crime Pattern Analysis. Urban Studies 37:4, The paper compares two methods of cluster analysis, STAC and SAGE, for the detection of crime patterns. The research found that STAC is useful for operational policing but ignores the underlying geography. SAGE does more in highlighting areas of interest for further investigation. However, SAGE requires a greater level of analytical skill and is not as widely available. Since SAGE was originally used for health-related research, the paper shows how great insight can be gained from transferring methodologies across disciplines. Even if one is not interested in details about these two methods of cluster analysis, the paper has much more to offer. It identifies three main areas of crime mapping applications (dispatching, community policing, crime analysis and resource planning) and provides a useful table on the typology of crime mapping applications. In addition, the authors provide practical information about geocoding which is important to many applications of GIS. Paulsen, Derek J To map or not to map: Assessing the impact of crime maps on police officer perceptions of crime. International Journal of Police Science and Management 6:4, This article discusses problems associated with the implementation and use of crime mapping which is rarely mentioned in other literature. The movement away from traditional centralized police operations towards a more intelligence-led proactive style of policing has led to an increased use of crime mapping. Police officers understanding of crime patterns and problem areas within a jurisdiction is the most important, yet also problematic aspect of intelligence-led policing. Research cited in this article has found that police officers perceptions of crime patterns and problem areas within a jurisdiction are at best marginal. This study attempts to answer the question, Will the distribution of crime maps improve officer perception and understanding of crime patterns and problem areas within a jurisdiction? Results indicate that simply providing officers with maps of crime distributions will not alone improve their understanding of crime patterns within

4 their jurisdiction. The author attributes the results to a lack of guidance about how to use the maps which lead to another major problem, officer buy-in and support. The author offers advice on how to remedy these problems, such as investing in officer training and infrastructure, to ensure that intelligence-led policing strategies succeed and the full capabilities of crime mapping are utilized. The article is clearly written including the discussion of the findings and explanation as to why these results may have been found. Poulsen, Erika and Leslie W. Kennedy Using Dasymetric Mapping for Spatially Aggregated Crime Data. Journal of Quantitative Criminology 20:3, In this paper, the authors look at ways in which data limitations can be addressed using dasymetric mapping applications. Dasymetric mapping can be used when researchers are working with aggregated data such as Urban Crime Reports. If address level crime data is available this technique is not needed. Dasymetric mapping involves estimating the distribution of aggregated data within the unit of analysis by adding additional information that provides insights on how these data are potentially distributed. The paper applies dasymetric mapping to estimate the spatial distribution of residential burglary within political boundaries in Massachusetts based on land use and housing data. Dasymetric mapping is also useful in creating density maps to reveal clusters of crime that are normally masked using chropleth mapping, a commonly used method to display aggregate data. This article is additionally valuable in revealing numerous sources of crime data. Ratcliffe, Jerry H The Hotspot Matrix: A Framework for the Spatio-Temporal Targeting of Crime Reduction. Police Practice & Research 5:1, The paper begins by outlining the available techniques, including location quotients and Local Indicators of Spatial Association (LISA), to identify the spatial and temporal components of crime hotspots and discusses improvements to these techniques. These methods are then applied to identify three broad categories of spatial (dispersed, clustered, hotspots) and three broad categories of temporal (diffused, focused, acute) hotspots. These categories are described in the form of a matrix. Although this analysis may be considered objective, it enables police officers to include both spatial and temporal factors in their thinking and will hopefully generate discussion about the best tactical approach to combating hotspots. In addition, it contributes much to the research of temporal hotspots which has received less attention than spatial hotspots. I would consider this necessary reading for anyone interesting in crime hotspots, as it is the first attempt to describe a typology of crime hotspots in a spatio-temperal manner. Vann, Irvin B. and David Garson Crime Mapping and Its Extension to Social Science Analysis. Social Science Computer Review 19:4, This article identifies and describes 20 GIS functions used in crime mapping. It is the authors opinions that, although most social data is spatial, GIS appears underused by social scientists. The authors propose how these crime mapping functions can be applied to social science research in hopes that more social scientists will utilize these functions in their research. The authors acknowledge that not every function is amenable to social science uses beyond police operations, but they find surprising versatility in these GIS techniques. Although the authors are focusing on the functions as uses for social sciences, I still believe the article is a great source for crime mapping

5 in that it provides descriptions of many GIS functions used in the field. Some function described in the article include: time-series mapping, hot-spot mapping, proximity mapping, spatial tracking, mapping spatial displacements, pattern detection, and mapping crime density.