The web-based Philadelphia Public Crime Mapping Application enables Philadelphia residents to search Police Department incident reports and generate maps of crimes throughout the city.

Client:  Philadelphia Police Department (PPD)

Challenge: The Philadelphia Police Department collects a large amount of crime data that the public has a legal right to access. While it serves the public’s interest to make this information available, the PPD also needs to protect victim confidentiality, and is thus unable to release detailed incident-level data for all crimes. Despite this concern, Commissioner Ramsey felt that the Police Department should make it easier for the public to access crime information.

Solution: Azavea created the Public Crime Mapping Application, a web-based application where the public can search, view, and download incident information via the Internet. The application enables users to search for a location by address, identify a crime type, and view up to 30 days worth of incidents on a map or in a table. A data download feature also enables anyone to download the data for more rigorous analysis.

One of the greatest challenges in creating the site was the need to display even relatively high volume of crimes at every scale. Viewing thefts city-wide, for a typical thirty day period, may result in 3,000 or more data points. The map depicting this situation would simply be a mass of undifferentiated points, which is not useful. To address this concern, the site uses a common cartographic technique of aggregation, which enables incidents in close proximity to be clustered, with dot size representing the number of incidents in an area. To ensure that the information is presented in a timely manner, a data transfer service was built to extract the information from the PPD’s database on a daily basis.

Outcomes: The Public Crime Mapping Application was brought from concept to a deployed application in less than two months. In the first month, there were more than 6,000 unique viewers from over 30 countries. By supplying crime data by city block, the system provides members of the public with valuable information about events in their communities and enables them to make informed decisions.