Mappiness pings users’ smartphones twice daily to ask how they’re feeling, and uses satellite positioning to discover their location while they answer. This simple procedure has generated a rich panel (longitudinal) data set, comprising millions of responses from tens of thousands of individuals. Although Mappiness was designed principally to investigate how we’re affected by our immediate environment, it can shed new light on a range of other questions in the social sciences and beyond — including the relationships between our happiness and work, cultural activities, terrorism, weather and football.