Crime Map Methodology

In mid-December 2006, I got an e-mail from an NBCA member asking if there was a web site which listed crimes by area. I went to the APD web site and see and found a surprisingly complete set of crime stats, both text and graphical.  (See www.atlantapd.org and then on the left menu bar mouse-over “Police & Community” and select “Crime Statistics” or “Crime Mapping”.)  The Atlanta Police Department is to be strongly commended for making this kind of data easily available to the public.

The web site’s “Crime Mapping” was especially intriguing.  It showed major crimes by type on a detailed street map and is a marvelous tool.  Or, at least, it is a marvelous starting point since there are some significant limitations to getting a big picture view of the neighborhood’s crime situation.  The major limitations were:

bullet One could only ask for between 1 and 14 days worth of data;
bullet The map is small (400 x 400 pixels); and,
bullet The street grid with street names disappears for maps wider than about ¾ mile. 

Still, it is a wonderful starting point, especially since the web site includes crime data by date, by type of crime, by location at the street level, and by Incident Number since the beginning of 2004.

I spent about 20 hours intensively working with these maps.  Ultimately, I made over 400 computer screen-prints which I digitally trimmed and stitched together into a set of high level maps.  The result of this effort is the preceding set of eight maps.  Since these maps cover almost a year and included a 4 2/3 mile by 4 2/3 mile square in the north part of the city, it provides the big picture view of North Buckhead crime within the context of other areas of Buckhead. 

The data shown is almost 100% from the APD – all I have done is accumulated 50 weeks worth of data, highlighted the North Buckhead neighborhood to make it easy to find and put easily readable street names on some of the major streets.  If you look at the maps with a magnifying glass you will see that almost all of the streets on the map have their names in tiny print.

 

Are there any shortcomings to the picture of crime shown on these maps?  Yes, there are several shortcomings:

bullet Whether there has been one crime or,. a thousand crimes during the year of a particular site (say, larceny from vehicle) at a particular address, there will only be one marker on the map.  This understates the apparent frequency of crimes, especially since some addresses, such as Phipps Plaza’s 3500 Peachtree Road represents hundreds of businesses and tens of thousands of parking spaces.  An ideal map would have bigger markers or different colors for more frequent crime counts.
bullet All crimes are marked at the edge of the street where the street address is.  Again, using Phipps Plaza as an example, all of its markers are shown immediately beside Peachtree Road even though the stores and parking decks are scattered all over the area bounded by Peachtree Rd - Wieuca Rd - Phipps Blvd - Lenox Rd.  
bullet The maps do not indicate population density.  For example there are few crimes shown in the area surrounded by Roswell Rd - Blackland Rd - Northside Dr - W. Paces Fy Rd - Habersham Rd.  It is not clear whether crime is as frequent there as elsewhere but is masked by the fact that the individual home sites are relatively huge.  An ideal map would provide some sense of the frequency of crime on a population-adjusted basis.

If you have any questions or comments, please send me an e-mail at Gordon@nbca.org.

Gordon Certain
President
North Buckhead Civic Association
February 21, 2007