Table 1.

Notations.

Symbol	Definition
$\mathcal{T}$	the set of targets: $\{t_1,t_2,\dots ,t_N\}$
S	the set of sensors: $\{s_1,s_2,\dots ,s_M\}$
$\mathcal{D}$	the distance constraint of sensors: $\{d_1,d_2,\dots ,d_M\}$
$\mathcal{U}$	a subset of sensors: $\mathcal{U}\subseteq \mathcal{T}$
$\mathcal{SU}$	the set of subsets: $\{{\mathcal{U}}_1,{\mathcal{U}}_2,\dots ,{\mathcal{U}}_K\}$
M	the number of sensors: $\left|\mathcal{S}\right|$
N	the number of targets: $\left|\mathcal{T}\right|$
K	the number of subareas: $\left|\mathcal{SU}\right|$
r	the sensing radius of sensors
$R(t)$	the sensing region of target t
$R(\mathcal{U})$	the intersection of $R(t)$ for all $t\in \mathcal{U}$