Using ESRI’s Districting Tool in Policing

From the Geography and Public Safety Bulletin



Environmental Systems Research Institute’s
(ESRI) districting tool1 is a free extension
for ESRI’s ArcGIS Desktop that allows analysts
to create new police districts in a city or region.
The redistricting tool initially was designed to
help governments draw congressional district
lines or create school districts, but has been
co-opted to help police departments outline
new beats. It helps them draw boundaries
and review the outcomes (e.g., predict new
workloads and crime rates) for the new districts.
The tool provides summary statistics for every
boundary selection. It does not automatically
create districts from preexisting data; rather, it
can be used to aid police communication and
make geographic information systems (GIS) a
central part of the redistricting process.
Preparing the Data
The ESRI districting tool requires an agency
to have GIS data entered as a polygon feature
class2 with attribute data. These polygons must
be smaller than the intended districts. Analysts
should use polygons that coincide with naturally
occurring boundaries and main thoroughfares.
Police departments must divide a city or region
into discrete boundaries to balance service and
distribute responsibilities into organizational
branches. This task requires departments to join
years of incident data (the point feature class)
to the chosen polygon feature class. This helps
ensure that a proportional number of incidents
is allotted to each geographic region.
The process of joining incident data to
polygons in ArcGIS to achieve a count of
incidents in each region is the same process that
an analyst would use to create a choropleth3
map that depicts different incident counts. To
join incident data to a polygon feature class, an
analyst should do the following:
1. Right-click the polygon layer...
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