If you look at the media's coverage of GIS and online mapping in the past month or two you'll see a crime wave. No, there's not necessarily more crime everywhere (though in many areas, it is up); there are just more crime maps online and more discussions about them. Here in the U.S. it seems a great many small towns, counties and large cities have, or will have, some type of online crime map in the coming months. I see at least one article each week in local, city or regional papers highlighting implementations. England and Wales launched an effort last summer to get all the police areas (43 in total) to provide online maps. The job was completed in the first week of January 2009.

Crime mapping seems to have more energy, more innovation and perhaps more connection to the citizenry than other public sector mapping efforts in recent memory. There's more buzz, more skepticism, more concern, more interest in the maps (though not necessarily in the technology behind them) than I recall when EPA's EnviroMapper or KnowledgePlex's DataPlace came on the scene. State websites, which tend to offer great data resources (I'm thinking of the MassGIS and the new Montana GIS portal, to name two), get buzz in the GIS community but typically don't set the public's interest aflame.

Let's face it: crime is special. The saying goes that all geodata are local. All crime is, too. Crime mapping encourages accountability. Accountability for the data collection, for the data sharing and for government response. I'll suggest that's the reason crime is a "hit" in the online mapping world, outpacing basic "complaint forms" and "local transit mapping" for news coverage, though those have been in the news, too.

One of the more interesting aspects of crime mapping is the diversity of solutions. By that I mean some solutions are built upon existing online mapping implementations, while others are completely autonomous. For example, some are managed by public servants; others are developed and maintained by online media sites or interested citizens; others are published by for-profit companies. Because crime and crime statistics are addressed and collected by different players under different jurisdictions using different processes, it can be difficult to find data, let alone find them in a consistent form that's easy to map. For example, some crime maps tap into 911 calls as their key source; others are less up-to-date because handwritten forms must be made digital before the data can be mapped or shared.

In this quick overview of crime mapping options I want to highlight two things: the variety of technologies and processes used, and the challenges crime map publishers face.

I want to start with the U.S. capitol. Washington, D.C. crime has been in the news recently, not because of the maps per se, but because of a change in policy that ended a longtime daily e-mail alert service which listed the nature and location of crimes. The assistant police chief explained the reason for the change revolved around the sharing of inappropriate data, that is, data that should not have been made public. Users of the e-mail service were pointed to a three-year-old, powerful crime map application built on the D.C. atlas as an alternative. D.C. has several other (some argue "better") crime mapping solutions including: the Citizen's Association of Georgetown map, last updated "Sun Mar 02 2008," per a recent visit, and CrimeinDC.org's crime map.

Despite the shutdown of the crime e-mail, many crime resources for D.C. remain online and up-to-date. EveryBlock is Adrian Holovaty's effort to gather local news and other "events" in selected cities. Here's the D.C. Crime Listing/Maps.

SpotCrime.org offers a map of D.C. and many other cities. There's not a lot known about the folks or technology behind it. CrimeReports.com charges law enforcement agencies (nominally based on population) to publish the data. The D.C. map is here. Both offer free maps based on Google Maps and data feeds for the public.

Next, to Asheville, North Carolina, where the crime mapping application runs against the same GIS used for other city needs. It includes the ability to find "hot spots" for various crimes, the ability to search by address, ZIP Code or PIN, along with buffers around those areas. There's also the ability to look at the history of different crimes over the past 11 months, a feature just recently added.

Asheville, N.C. offers "heat maps" of crimes, along with buffering and historical graph charts (not shown). (Click for larger image)

Down south, New Orleans is still getting back on its feet and the police department's online crime maps are dated. I was unable to access data past Dec 28, 2008. The city's site is out-of-date, mostly because of processing, per newspaper accounts. Reports are done by hand, then must be confirmed and sometimes updated before they are scanned into digital form. That means the site can be 15 days or up to two months out-of-date according to a study by WWL-TV.

City of New Orleans Crime Map - Despite being able to query the current date, the "newest" crime I found was on Dec 1, 2008. (Click for larger image)

The delay led one citizen, Brian Denzer, a GIS practitioner, to build www.citizencrimewatch.org. He updates it himself from a variety of sources and is generally about two days behind.

French Quarter resident Thom Kahler, who runs the Web site N.O. Crimeline, until recently used data from the 8th district provided by agreement with the local district commander. The data were delivered to Kahler, who mapped them and sent out an email (with editorial comment) detailing the crimes. The agreement ended in January. Why? Two different explanations appear: one involved a request from the Times Picayune newspaper for data on all the districts, which the police felt was too much work. Another suggested Kahler's editorializing was inappropriate.

Jefferson Parish's crime maps (the parish next door to Orleans Parish, in which New Orleans is located [corrected 1/15/09]]), delivered by an app called Crime Tracker, are updated daily at 3:00 am from 911 calls. When I visited, queries were only available based on 2007 and 2008 and I was unable to generate a map that included any crime, after several visits using different hardware and software.

Finally, let's jump to the United Kingdom, where the Home Office mandated that each of the 43 Police Authorities in England and Wales make their crime data available on online maps. In West Yorkshire the tools for querying an area for a specific type of crime are easy to use. However, the Authority has not confirmed that posting locations on a map maintains privacy in burglary situations, and thus offers just a list. London's Metropolitan Police serve their maps via a Google Maps application.

West Yorkshire's Police Authority maps most crimes, but due to privacy concerns, does not yet post burglaries on a map. (Click for larger image)

London's crime maps take advantage of Google Maps. Note that the map reflects data from November 2008. (Click for larger image)

Conclusions
Crime data have been collected and mapped for centuries...and they are still of great importance to citizens. How the data are collected and shared publicly online varies quite a bit in:

• who does the mapping
• the technology used
• ease of use
• timeliness of data available
• how privacy concerns are addressed