Are Measures of Patrollability Affected by Tessellating Shape

Abstract

A grid-based thematic map is a spatial analysis tool that can be used to identify crime patterns, aiding law enforcement agencies in identifying problem areas within their jurisdictions and allocating resources to address them. Grids used to create these maps are comprised of shapes that tessellate (i.e., squares, hexagons, triangles). Square grids are used most often in crime hot spot mapping, but little is known whether the choice of tessellating shape affects performance metrics used to assess prospective hot spot forecasts. Using a purposive sample of known crime locations in St. Petersburg, Florida, the current study investigated whether tessellating shape used in grid-based thematic maps affects one particular performance metric: patrollability. Findings were mixed, showing that the effect tessellating shape has on grid-based thematic maps varies by type of crime and on which patrollability metric is used to assess forecasting performance. Results are discussed in terms of their impact on practioners' use of crime hot spot mapping in law enforcement and on future research.