Where’s everybody? Comparing the use of heatmaps to uncover cities’ tacit social context in smartphones and pervasive displays

We introduce HotCity, a city-wide social context crowdsourcing platform that utilises user’s current location and geo-tagged social data (e.g., check-ins, “likes” and ratings) to autonomously obtain insight on a city’s tacit social awareness (e.g., “when is best time and where to go out on a Saturday night?”). HotCity is available as a mobile application for Android and as an interactive application on pervasive large displays, showcasing a heatmap of social buzz. We present the results of an in-the-field evaluation with 30 volunteers, of which 27 are tourists of the mobile app, compare it to a previous evaluation of the pervasive display app and also present usage data of free use of the pervasive display app over 3 years in the city of Oulu, Finland. Our data demonstrate that HotCity can communicate effectively the city’s current social buzz, without affecting digital maps’ cartography information. Our empirical analysis highlights a change in tourists’ foci when exploring the city using HotCity. We identify a transition from “individual [places]” to “good [areas]” and “people [choices]”. Our contributions are threefold: a long-term deployment of a city-wide social context crowdsourcing platform; an in-the-field evaluation of HotCity on mobile devices and pervasive displays; and an evaluation of cities’ tacit knowledge as social context as a denominator in city planning and for the development of future mobile social-aware applications.