2.1.1. Target Motion Model

Without loss of generality, the considered target moves on the 2D plane with a nearly constant velocity, and the evolvement process of the target state is given as

$$\mathbf{x}\_{k} = \mathbf{F}\mathbf{x}\_{k-1} + \mathbf{w}\_{k} \tag{1}$$

where *x<sup>k</sup>* = [*xk yk* . *xk* . *yk*] *<sup>T</sup>* represents target state including position component *pos<sup>k</sup>* = [*xk yk*] <sup>T</sup> and velocity component *vel<sup>k</sup>* = [ . *xk* . *yk*] T . The subscript *k* denotes sampling time and T is the sign for vector transpose. *<sup>F</sup>* is the state transition matrix. *<sup>w</sup><sup>k</sup>* ∼ N(*w*; **<sup>0</sup>**, *<sup>Q</sup>*) represents the multi-dimensional Gaussian process noise vector, where N(ζ; μ, **Σ**) denotes Gaussian function with variable ζ, mean μ and covariance matrix **Σ**. *F* and *Q* can be further written as Σ Σ

$$F = \begin{bmatrix} 1 & 0 & t & 0 \\ 0 & 1 & 0 & t \\ 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 1 \end{bmatrix}, \mathbf{Q} = q^2 \begin{bmatrix} t^4/4 & 0 & t^3/2 & 0 \\ 0 & t^4/4 & 0 & t^3/2 \\ t^3/2 & 0 & t^2 & 0 \\ 0 & t^3/2 & 0 & t^2 \end{bmatrix} \tag{2}$$

where *t* is the sampling interval and *q* is the acceleration variance.
