Graph-based filtering of ballistic trajectory

In the context of team sport events monitoring, the various phases of the game must be delimited and interpreted. In the case of a basketball game, the detection and the tracking of the ball are mandatory. This paper deals with the detection of the ballistic trajectory of a ball thrown between two players or toward the basket. Ballistic trajectories build on the 3D ball candidates previously detected at each timestamp. The proposed method is based on a graph, for which the nodes are the observed velocity between two 3D candidates, the edges link two nodes that have a common 3D candidate and the cost function is proportional to the distance between the observed acceleration and the gravity one. Hence, looking for the shortest path in this graph is equivalent to searching for 3D candidates that follow a ballistic trajectory. It appears to be both quite efficient and effective.