An urban park is a free or low-cost setting of physical activity with convenient access. While various monitoring techniques such as direct observation or video recording have been developed, there is no study using Unmanned Aerial Vehicles (a.k.a. Drones) in parks. UAVs in studying park use could save time and money as it covers a greater area in a shorter time. Thus, this research develops a new observation method in monitoring park-based physical activity.