From Phototrails.net. The images there are interactive, and graphed in different ways to show different types of data.
Below is a plot of photos taken/posted over a 24-hour period of time from Brooklyn. (Time is the angle, hue is distance from center. Time span is from 4:35 AM, 10/30/12 to 4:35 AM, 10/30/12) Notice the distinct line at about 10:30 PM (roughly 45 degrees from the right).
In case the date doesn't jog your memory ... that was when the power went out during Superstorm Sandy...
