A moving region whose location and extend change over time can imply topological changes such as region split and hole formation. To study this phenomenon is useful in many applications, e.g. the topology control of wireless sensor networks and emergency handling. It is challenging to detect the topological changes of a moving region since we lack the ability to capture its continuous change of shapes all the time. Moreover, for a complex moving region containing multiple components, it is hard to determine which component before the change corresponds to which component after the change. In this paper, we propose a model to determine topological changes of a complex moving region through snapshots called observations. We introduce a twophase strategy that the first phase partitions the observations into several evaluation units and uniquely maps a unit before the change to exactly one unit after the change; the second phase interprets the topological change by integrating all basic ...