Using Geospatial Mapping and “Hot Spots” to Fight Crime

Introduction:

The origin of using GIS in policing began decades ago with pushpin maps. Detectives would use these pushpin maps to try and find

geographic patterns to a series of crimes that would hopefully lead them to the perpetrator. It was an inexact science with only obvious visible

patterns being identified. It was used largely in high profile serial murders, serial robberies, and serial burglaries where one suspect or group

of suspects was thought to have committed numerous crimes. Recently, however, the advent of computers and modeling has led to many more

uses including deployment of resources and even predictive policing. This project will look at crime in San Francisco, specifically robberies

and crimes involving weapons to illustrate how the identification of patterns can lead to more efficient deployment of resources for SFPD.

*All data compiled from the SFGIS online catalogue (http://gispub02.sfgov.org/)

Background Information: San Francisco is broken up into nine districts and 51 sectors serviced by

approximately 2,370 officers. Although the exact number of officers on the

street at any given time is unknown, with 51 sectors, I would approximate 120+

officers on the street at any daytime hour (many “beat cars” having 2 officers

riding in each car plus supervisors, street crimes, mounted units, traffic units,

etc.). These first two maps show the districts, sectors, and a short range area of

coverage for the police stations. Although normally most police officers are on

patrol in their area of responsibility, major calls would have officers in the

station responding.

Robberies: For robberies, I ran Hot Spot Analysis and it showed three main problem

areas. The first was almost identical to one of the “Weapons” hotspots:

the block bounded by Mission St. in the west, 15th St. in the north, Capp

St. in the east and 16th St. in the south. The second area was O’Farrell

Street and Geary Street just west of Market Street. The last area is

centered on the intersection of Hyde St. and Ellis St. With the specificity

of hot spots, undercover officers and uniformed officers on directed

patrol can focus on these areas for greater efficiency.

Weapons Charges: While data from one month (October) is not ideal, it shows trends that could

help locate areas to saturate with police for crime prevention. I began by

running Hot Spot Analysis on arrests that included weapons charges. The hot

spots were predominantly limited to three smaller areas: the intersection of

Geary St. and Larkin St., the area near Taylor St. and Eddy St., and the block

bounded by Capp St. in the west, 15th St. in the north, South Van Ness Ave. in

the east and 16th St. in the south. With this type of specificity, directed patrols

including heavy probation and parole stops could significantly impact weapons

related violence in the city.

Conclusion: The most heavily concentrated areas for crime were in the Tenderloin,

Northern, Central, Mission and Southern Districts. While this is not news to

any police officers that work in these areas, this project looked at the

possibility of getting enough specificity in where the true “Hot Spots” are that

patrol officers and other ancillary units could effectively target certain blocks

for heavy enforcement to break up hot spots and make the community safer

for its residents. The next step would be trying to take this information and

put in use at the command level to see how effective it might be it making

patrols more efficient.

Three Hot Spots for Weapons Violations Three Hot Spots for Robberies

Analysis conducted by: James Baird