Phototrails project shows cities’ Instagram fingerprints

Kelly O'Mara

We know that our Instagram photos say something about us as individuals (usually, we hope what they’re saying is: I’m cool and attractive and fun). But as we’re snapping pictures of our food, we probably haven’t thought about what those photos say about our city as a whole.

A new research project from the University of Pittsburgh, the California Institute for Telecommunication and Information, and the Graduate Center at City University of New York is trying to answer that question. Analyzing 2.3 million public Instagram photos, the project — Phototrails — is working to understand what data can be gleaned from snapshots, publishing its findings in the peer-reviewed journal First Monday at the beginning of July.

Using open-source software, Phototrails sorted the photos from 13 different cities by time, location, hue, brightness and a number of other factors. The idea is to make visualizations of each city and see what differences they reveal.

For each city — from Tel Aviv to New York to Bangkok — the group created a visual signature made up of 50,000 photos from that city, plotting the mean brightness of the photos along the radius and the mean hue along the perimeter.

“Our visualizations allow us to uncover the aggregated visual characteristics of each city as well as to examine the impact of exceptional events such as Hurricane Sandy,” said Nadav Hochman, a Ph.D. student in the History of Art and Architecture department at the University of Pittsburgh.

The project also plotted photos by time and geography to study the differences during major national events in Tel Aviv and to measure the visual cycles from day-to-day. They even plotted visual representations of individual usage over three months. Each dot represents an individual’s location, with colors indicating time and lines connecting photos that were taken within the same hour.

All of this creates interesting and eye-catching representations, but what those can be used for isn’t exactly obvious yet.

One clear-cut analysis uses the photos to show what happened in the wake of Hurricane Sandy. When researchers plotted the photos from a 24-hour period in the Brooklyn area by time and hue, a clear line demarcated the worst of the storm. There is a distinct change in the number and color of photos after the power outage. This kind of tool could be important in the future in understanding how crises play out on the ground.

There are still plenty of questions. Why is the visual signature for New York so different? Why are San Francisco and Tokyo so similar? What does it all mean? That’s something no one knows yet.