1. A method of tracking entities using a single overhead camera comprising the steps of: detecting a foreground region in a video frame of the single overhead camera corresponding to one or more entities; determining if the foreground region is associated with an existing tracker; determining whether the detected foreground region is the result of at least one of a merger of two or more smaller foreground regions having corresponding existing trackers and a split of a larger foreground region having a corresponding existing tracker when the detected foreground region is not associated with an existing tracker; and tracking the detected foreground region via at least one existing tracker when the foreground region is at least one of associated with an existing tracker and the result of at least one of a merger and a split; wherein the step of detecting a foreground region comprises the steps of: differentiating foreground pixels and background pixels to create a first foreground region; fitting an ellipse around the pixels of the first foreground region; filling the pixels in the ellipse around the first foreground region to create a second foreground region; determining whether the number of pixels filled is less than half of the pixels within the ellipse; using the second foreground region as the foreground region when the number of pixels filled is less than half of the pixels within the ellipse; and using the first foreground region as the foreground region when the number of pixels filled is not less than half of the pixels within the ellipse wherein the above steps are performed via a processor.