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人群密度方面的综述.pdf

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Robert Collins Penn State Crowd Scene Analysis • Using computer vision tools to look at people in public places • Real-time monitoring – situation awareness – notifications/alarms • After-action review – traffic analysis VLPR 2012
Robert Collins Penn State Crowd Scene Analysis Things we might want to know: • How many people are there? • How to track specific individuals? • How to determine who is with whom? Challenges: Crowd scenes tend to have low resolution. You rarely see individuals in isolation. Indeed, there are frequent partial occlusions. VLPR 2012
Robert Collins Penn State Crowd Counting FAQ: How many people participated in ... • Tahrir Square Protests • Obama’s inaguration • Occupy Wall Street • Kumbh Mela VLPR 2012
Robert Collins Penn State Jacob’s Method • Herbert Jacobs, Berkeley, 1960s • count = area * density – 10 sqft/person – loose crowd (arm’s length from each other) – 4.5 sqft/person – more dense – 2.5 sqft/person – very dense (shoulder-to-shoulder) • Problem: Pedestrians do not uniformly distribute over a space, but clump together into groups or clusters. • Refinement: break area into a grid of ground patches and estimate a different density in each small patch. Accumulate these counts over whole area. VLPR 2012
Robert Collins Penn State Example of Jacob’s Method VLPR 2012 source http://www.popularmechanics.com/science/the-curious-science-of-counting-a-crowd
Robert Collins Penn State Computer Vision Could do Better! Cavaet: nobody really wants accurate counts e.g. organizers of the “Million Man March” in Washington DC threatened to sue the National Park Service for estimating that only 400K people attended. VLPR 2012
Robert Collins Penn State Vision-based Counting • detection and tracking (light density) • clustering feature trajectories that move coherently (moderate density) • treat crowd as a dynamic texture and compute regression estimates based on measured properties (heavy density) VLPR 2012
Robert Collins Penn State Detecting and Counting Individuals Ge and Collins, "Marked Point Processes for Crowd Counting," IEEE Computer Vision and Pattern Recognition (CVPR'09), Miami, FL, June 2009, pp.2913-2920. Good for low-resolution / wide-angle views. Relies on foreground/background segmentation. Not appropriate for very high crowd density or stationary people. VLPR 2012
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