SOPARC provides observational user data and contextual information on the setting in which the physical activity occurs. During a scan (i.e., an observation sweep moving from left to right) the physical activity of each individual is coded as sedentary (i.e., lying down, sitting, or standing), walking, or vigorous. These activity codes have been validated using heart rate monitoring and by accelerometry in physical education classes with children and youth in kindergarten through twelfth grade14 (link), 15 (link). The activity codes are also consistent with published energy expenditures for adults 16 (link). People are counted only if they are in a specified target area at the time of the scan and their level of activity at the moment of observation is recorded. Separate scans are made for females and males. The predominant type of activity in each area that females and males are engaging in also is recorded, drawing from a pre-developed list of activities (e.g., basketball, football).
Two neighborhood parks from each of five cities which provided geographic and demographic diversity were selected for observation (Los Angeles, CA, Albuquerque, NM, Durham, NC, Columbus, OH, and Philadelphia, PA). Neighborhood parks are the recreational and social focus of communities and considered by city planners to be recreational and social centers and comprise the basic unit of the park system17 . Parks were chosen from diverse income areas and observed during 2008. Park characteristics and seasons of observation are described in Table 1. Socio-demographic characteristics of the ½ mile area surrounding the park were obtained from block group data from the US 2000 Census18 . The 10 parks were mapped into 274 discrete target areas, which included such facilities as basketball courts, tennis courts, and playgrounds. Having target areas facilitated observations and allowed for the documentation of the how different park areas were used.