GIS4048 Module 5: Homeland Security - Washington, DC Crime

The purpose of this module was to perform as a District of Columbia Metropolitan Police Department GIS Analyst who is responsible for crime analysis. The goal was to help allocate resources by analyzing January 2011 crime statistics for DC. Specifically, the project involved determining the following:

• whether current patrols are effective as is or need to be altered based on crime patterns in proximity to police stations
• patterns of aggravated assault, homicide, and theft-related crimes

The first map depicts each existing police station's location and percentage of the District of Columbia's total crime for the month. The locations of individual crimes were included for a visual comparison of crimes in relation to existing police stations. Proposed police station locations were based on analysis of crimes in proximity to existing stations, proximity of stations to other stations, and availability of land or existing building for a new station.

Proposed police station locations were based on the data showing that most crimes occur 1/2 to 1 mile from a police station. This was done by applying a multiple ring buffer around each station before performing a spatial join between the crime data layer and the buffers. The 6th and 7th District police stations both had relatively high percentages of crime occuring close to them. Having lived in southeast Washington in the past, I know that that area's reputation for higher crime rates in general is common knowledge to District residents. (One of my roommates there was mugged not once, but twice. In the same night.) The proposed location south of the 7th District police station was selected because of the 7th’s highest rate of crime occurring close to it along with the numerous crimes that have occurred in extreme southern DC south of the 7th District where no police stations are located currently. (A large empty parcel is situated at Mississippi and 10th Place SE). Wherever an additional station to reduce crime around the 7th District is located, it should be east of the Anacostia River to minimize response time.

Also in southeast Washington, the 6th District has a relatively high crime rate occurring near it as well, but perhaps personnel could be transferred from the 6th Substation, 1st District Station, or 1st District Substation, all of which have significantly lower crime rates than the 6th District.

Additionally, DC would benefit from having another station located south of the 3rd District police station (12.56% of total crimes) and west of the Asian Liaison Unit with its 9.1% crime rate occurring in its neighborhood. There is a lot of overlap of police station buffer zones north of the 3rd District station and east of the Asian Liaison Unit, but the areas south of the 3rd District and west of the Asian Liaison Unit have a significant number of crimes and there is no other police station from that area all the way out to the DC boundary. The area of 20th St. NW and L St NW has commercial buildings which might have sufficient space available to accommodate a substation. Percentages of crime, police station locations, and proposed station locations area shown on the first map:

Analysis of Crimes Committed in District of Columbia in January 2011

The density maps of burglaries, homicides, and sex abuse crimes were created using the kernel density method with a radius of 605 (area in square kilometers). The density maps reveal similar patterns to those shown with the previous map: higher concentrations of crime in the southeast quadrant of DC as well as central DC.

Density Maps of Burglaries, Sex Abuse, and Homicides
in Washington DC (January 2011 data)

In general, theft in its various forms, burglary, and robbery were the most common crimes. Because these maps were created by a DC MPD department GIS analyst and are intended for internal use, a locator map was not included. The first map is a bit busy with the locations of individual crimes shown, but seeing those locations of specific crimes helps determine patterns, and the visual aspect reinforces the statistics and written analysis. Some portions of the District of Columbia are noticeably free of crime incidents. Among other reasons, this may be due to those areas being green spaces where fewer incidents of robbery and theft-related crimes would be expected. Another reason is that there are many federal parks (Presidents’ Park, The National Mall, The Ellipse, etc.) in DC which are patrolled by US Park Police. I suspect that crimes handled by US Park Police are not included in the DC police department statistics.

This module was very extensive and very informative. Again, the value of GIS and the wealth of information that can be illustrated with GIS was demonstrated. Throughout this module, much experimentation was done to find optimal color schemes, labeling techniques, layer order, transparency, and so forth to determine the most optimal combination to illustrate the information clearly and completely. A feature that was especially invaluable for this particular analysis was the Identify feature. As in other modules, this experience has left me with the desire to know how to accomplish other things in ArcGIS.