3.2.2. Trajectories Pruning

For a set of estimated trajectories tuples from filtering stage <sup>T</sup><sup>ˆ</sup> <sup>=</sup> {(<sup>ˆ</sup> *l*1, ˆ *b*ˆ *l*1 , ˆ *ξ*ˆ *l*1 ), ...,(ˆ *lN*, ˆ *b*ˆ *lN* , <sup>ˆ</sup> *ξ*ˆ *lN* )} the lifetime of a trajectory with label ˆ *ln* is the length of the corresponding association history, which is given as follows:

$$\pi(l\_n) = f\_{length}(\mathcal{J}\_{l\_n}) \tag{26}$$

where *flength*(·) is the function that determines the length of the vector in its argument. If the length of a track is shorter than the threshold value *τt*, i.e., *τ*(*ln*) < *τt*, this trajectory will be removed from the set of estimated trajectories.
