Fig. 1

Definition of activity settings and overview of the assignment process. Legend: Using the point-in-polygon overlay in ArcGIS, each participant’s data point was assigned to one of the eight activity settings. This assignment process was conducted in a hierarchical order using six location layers. Each layer was created using further geospatial data provided by the Office for Geomatics and Surveying of the City of Zurich: By means of land use data, we digitalized the urban area of Zurich within a new layer boundary. The assessed home addresses from all participants were geocoded using Google Maps and plotted on the layer home. Within this layer, we created a 30 m Euclidian buffer around each geocoded home point to define home polygons. By using the points-of-interest file containing the location of all schools in Zurich and with the help of register data and satellite imagery, we manually digitalized all school grounds of any public school in Zurich and summarized them in the layer school. To take the measurement error of the GPS devices into account, we drew a ten meter buffer around each school polygon. The analogous procedure was carried out to construct a polygon layer containing public parks and playgrounds (park), and one layer containing sports facilities (sport). To create the layer street, we used land use data and selected all surfaces such as streets, sidewalks, cycle or pedestrian paths and drew a ten meter buffer around each polygon