1. A method for multi-target tracking of targets for a sensor system generating a sequence of successive data frames, each comprising a set of observations representing data collected by the sensor system during a sensing period, comprising a sequence of the following steps: receiving the first frame and setting up a set of tracks in dependence on the data comprising said first frame; for each successive frame received, performing the following steps: deleting stale data regarding said previously received frames; processing the observations in the new frame to generate a new set of tracks based on said new set of observations as well as observations received from previous frames; and generating a fresh set of hypotheses each comprising a set of tracks such that no two tracks within any hypothesis have any observations in common.