NCJ Number
227217
Journal
Geography & Public Safety Volume: 2 Issue: 1 Dated: May 2009 Pages: 9-10
Date Published
May 2009
Length
2 pages
Annotation
This article describes the tools that can be used to process data from a global positioning system (GPS) that tracks the location of sex offenders.
Abstract
The California Department of Corrections and Rehabilitation has begun tracking more than 6,000 sex offender parolees by using GPS anklets. The GPS device lets parole officers know when parolees are in restricted areas by logging GPS coordinates every minute and sending coordinates to a central server every 10 minutes. This information about parolee location is compared to law enforcement incident data through crime-scene correlation reports. Law enforcement and parole agencies need a means of summing vast amounts of spatial behavior and coordinating it with related crime information. Environmental Systems Research Institute's (ESRI) Modelbuilder and the kernel density tool are essential for analysts who track and analyze sex offender movement data. Crime analysts use the kernel density tool to visualize and define groups of crime. The use of this tool enables "anchor points" for crime to be merged with a larger set of anchor points for a particular parolee, such that geographical locations and times for crimes can be compared to the location of the parolee at the time and location of a crime. ESRI's Modelbuilder is essential for analyzing sex offender anchor points. Once the model has been created, the process is run repeatedly for thousands of tracked offenders, and anchor point databases will continue to grow. Anchor points can drive tracking analysis and serve as points of communication between local law enforcement and regional parole offices. When an offender is in the vicinity of a crime, parole agents and crime analysts receive incident hit notification e-mails, which might say, as an example, "A parolee tracked by the system is within 1,500 yards and 30 minutes of a time-stamped crime incident." 3 figures and 2 notes