Criminal Geographic Targeting (CGT)
Definition
Kim Rossmo's algorithm for geographic profiling, incorporating a distance-decay function modified by a buffer-zone suppression factor; implemented commercially in the Rigel software.
- Developer
- Kim Rossmo
- Mechanism
- Distance-decay function with buffer-zone suppression
- Commercial software
- Rigel
- Field
- Geographic profiling
Common questions
Why does the CGT algorithm suppress probability near the offender's likely anchor point?+
Offenders typically avoid committing crimes very close to their home or anchor point to reduce the risk of being recognised, so the buffer zone lowers the predicted probability in that immediate area even though distance decay alone would otherwise favour it.
Is Rigel software output treated as a precise location prediction?+
No. It generates a probability surface, often called a jeopardy surface, that ranks areas by likelihood of containing the offender's anchor point, and is used to prioritise investigative resources rather than to pinpoint an address.
Related terms
- Buffer Zone
- The area immediately around an offender's anchor point where offence probability is suppressed because the offender avoids committing crimes near recognisable locations...
- Circle Hypothesis
- David Canter and Paul Larkin's 1993 hypothesis that for marauder offenders, the anchor point falls within the circle defined by the two...
- Commuter
- An offender who travels from their anchor point into a geographically separate crime area to offend; the circle hypothesis does not reliably...
- Distance Decay
- The empirical observation that the probability of an offence location decreases as distance from the offender's anchor point increases, reflecting the rising...
- Geographic Profiling
- A spatial analysis technique originally developed by Kim Rossmo that predicts the likely home or anchor point of a serial offender from...
- Jeopardy Surface
- The probability map output of geographic profiling, rendered as a colour-coded topographic display where high-probability zones for the anchor point appear in...
- Marauder
- An offender who operates radially from a fixed anchor point, committing crimes within a radius around that point and returning to it...
- Rigel
- The commercial software implementing the CGT geographic profiling algorithm, developed by Environmental Criminology Research Inc. in Vancouver and licensed to law-enforcement agencies...