Monday, July 16, 2012

60 Steps Revisited: Step 24 - Know When To Use High-Definition Maps

Back in 2009, I did a series of posts covering the excellent book Crime Analysis For Problem Solvers. The book is published by the US DOJ's Problem Oriented Policing Center (POP Center). Because of the value I think this book has for crime analysts, and policing in general, I am going to re-post this series on here on the blog.

In this post in our journey through Crime Analysis For Problem Solvers we're going to cover Step 24 - Know When To Use High-Definition Maps. As computers become more powerful and mapping software becomes more ubiquitous, we're seeing an explosion of crime mapping. However, crime mapping does have some limitations.

Most Department's crime mapping is done based on address data found in their Records Management Systems. One common problem is due to the way that crimes locations are recorded. For instance, there is a large indoor shopping mall in the jurisdiction where I work. This mall, also has a number of outbuildings around it's perimeter. In spite of this very large area, with numerous buildings, they all have the same physical address. When the crime is entered into the Computer Aided Dispatch (CAD) system with the same address regardless of where it occurred on the complex. In fact, incidents happening on one side of the property are about one half mile away from incidents happening on the other end.

If you have problematic crimes occurring at a similar large facility in your city, you may need to use high-definition maps to adequately study the problem. The authors of Crime Analysis For Problem
put it this way:

Mapping might therefore suggest that a particular building or facility has a crime problem, but this may only be because it is so large. When account is taken of the many people working in the building or using the facility, it could prove to be relatively safe. For example, George Rengert showed that a parking garage in central Philadelphia identified as an auto crime hot spot actually had a lower rate of auto crime than the surrounding streets, once account was taken of the large number of cars that could be parked in the facility.
A solution to this problem is to use high definition maps to precisely locate these incidents on a map of the facility. The authors give an example of a college campus where an effort to precisely identify crime locations led to this interesting finding.
Crimes recorded by the campus police were then plotted exactly where they occurred, allowing them to be related to environmental features such as poor lighting or a blind corner allowing the attacker to lie in wait.
For most Departments and most crime problems, this kind of high-definition mapping is likely to be a bit of overkill. But it should be another technique to put in your crime analyst's toolbox should the occasion for it's use arise.

Next time, we'll cover Step 25 - Pay Attention To Daily And Weekly Rhythms.

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