Editor's note: Last year, the City of New York enacted legislation requiring the creation of a crime map that the public could use to get information about safety on city streets. The Department of Information Technology and Telecommunications (DoITT) worked with the New York Police Department (NYPD) to create an interactive visualization of crime trends in the city. Today we hear from Colin Reilly, Director of DoITT’s Geographic Information Systems (GIS) Unit, who led the team that developed the map.

For a bustling city of more than eight million, New York City has remarkably low crime rates — it’s the safest big city in the country. However, that doesn’t stop the government from always looking for new ways to keep the public safe.

Last year the city passed a law requiring the Department of Information Technology (DoITT) to create an interactive crime map. The ability to visualize crime incidents empowers people to make informed decisions about their safety. Additionally, publishing the data in such a public and accessible way makes each precinct more accountable for crime in its area.

With these goals in mind, we worked with the NYPD to release the NYC Crime Map. We used Google Maps Engine to layer information about specific crime incidents – including felonies like murder, rape and theft – on top of a Google Map. Now New Yorkers have a tool at their fingertips to quickly assess the safety of their surroundings through the familiar Google Map interface. People planning a move can search specific addresses before relocating. Neighborhood and community organizations use the map to view patterns over a certain period of time to understand, for instance, whether crime has increased in the area of a new nightclub.

The default map view lets you zoom in and out to quickly see the crime rate for a particular area. You can search for crimes by type and date range. We’ve also added a heat map that color codes crime incidents per 1,000 residents, which makes it easy to compare the concentration of crime by precinct or location. Previously, the police department posted raw data – such as listings of crimes, dates and addresses, on a website. The new, intuitive map interface visualizes these statistics by geographical area, type, and date, making it much easier to read and overall more helpful for New Yorkers.

Before starting the project we assessed several open-source tools, but we chose Google Maps for Business because it allowed us to develop the map quickly and without the need for specialized GIS skills. Google hosts all of the data in the cloud as well, which allows us to focus on our core mission – developing innovative technology solutions for the New York City. Thanks to Google Maps, the NYC Crime Map can handle large volumes of traffic – a third of which comes from mobile devices – which we couldn’t have managed on our own.

The NYC Crime Map is part of a larger citywide campaign to be more transparent and accountable to the public. With the easy-to-use interface the NYC Crime Map provides, policymakers and the public they serve are provided a clearer view into the safety of neighborhoods across the five boroughs.