There are many video analysis applications in which the flow of people or traffic over time is of more interest than tracking the discrete objects contained. Motion pattern maps, loosely called heat maps, can show accumulated activity over time via temporal filtering. In this paper, we examine three parameters that control this filtering with respect to: event resolution, time-merging of events, and dynamic background. Design of these parameters is detailed and their effects are shown on simulated videos. Design considerations for real video events are discussed and shown by example.