Module 1 - Crime Analysis

 

Image 1. Grid Overlay Hotspot Mapping

Image 2. Kernel Density Hotspot Analysis

Image 3. Local Moran's Hotspot Mapping

This first lab used our GIS skills to map crime incidences in both Washington and Chicago. In the last part of the lab, we explored three different techniques, Grid Overlay, Kernel Density, and Local Moran’s I hotspot mapping, to analyze which would be most efficient in predicting future crime from the perspective of a police department allocating resources.

To complete this analysis, I created three different hotspot maps using the 2017 homicide data for Chicago. I began with the grid‑based hotspot method by joining the homicide points to the half‑mile grid cells, selecting only the cells with at least one homicide, and then identifying the top twenty percent with the highest counts. I dissolved these selected cells into a single polygon to represent the grid‑based hotspot. Next, I created a kernel density hotspot by running the Kernel Density tool with the appropriate parameters for Chicago, adjusting the symbology to isolate values at or above three times the mean, reclassifying the raster into two classes, converting it to polygons, and selecting only the highest‑density areas. For the Local Moran’s I hotspot, I joined the homicide data to the census tracts, calculated homicide rates per one thousand housing units, and ran the Local Moran’s I tool to identify statistically significant high‑high clusters. I selected those clusters and dissolved them into a single boundary. These three hotspot methods provided different outlines of where homicides were concentrated in 2017, which I later compared to the 2018 homicide locations to evaluate how well each method predicted future crime.

The Local Moran’s hotspot would not be a great future predictor because, although it has a high number of 2018 homicides, this occurred over a very large area of 52.67 square miles. This is too broad and unable to pinpoint resource allocation accurately.

The Grid Overlay and Kernel Density data are relatively similar, with smaller areas and a large number of 2018 homicides. However, the density calculation is the dealbreaker here, with a high concentration of crime that is useful for a police chief to allocate his resources. Due to this, the Kernel Density hotspot analysis technique is the best to use as a production of future crime and allocation of resources.