A method and apparatus for analyzing a sequence of images. Signal-to-noise ratios are identified for potential tracks using a tree having hierarchies of nodes identifying potential positions for an object over a period of time and using the sequence of images. Each hierarchy in the hierarchies of nodes represents a time and the potential positions in the tree form the potential tracks for the object. A potential track is selected from the potential tracks as an established track for the object using the signal-to-noise ratios, and a detection of the object is reported.