Inspired by the animated wind map that was posted a little while ago, professional programmer Jeff Clark has explored how people move about in a city. The result, titled Movement in Manhattan [neoformix.com], visualizes the speed and direction of Twitter users in Manhattan, New York.
The visualization is based on a large collection of geo-located tweets that were sent in a 4-hour time-window by the same users. These tweets were used as samples that together construct a vector field representing the average flow of people within a specific area. Particles, representing people, were released at locations where actual tweets were recorded and their subsequent movement was determined by the flow field.
The lines are thus traces of these moving particles, which start out blue and gradually change to red to show the direction of movement.Locations where there is little movement will have blue dots or very short blue traces. Longer traces with more red show a greater speed at that point.