In surveying the images of cities presented on the public image-sharing website Flickr.comTM, certain subjects appear with surprising frequency, inspiring reflection and research questions. For example, anecdotal observations by one of the authors seem to indicate that food, from items on display in outdoor markets to meals about to be eaten in restaurants, is a popular theme with Flickr users....

Particulate Matter (PM) is a form of air pollution that visually degrades urban scenery and is hazardous to human health and the environment. Current monitoring devices are limited in measuring average PM over large areas. Quantifying the visual effects of haze in digital images of urban scenery and correlating these effects to PM levels is a vital step in more practically monitoring our enviro...