The bearing-only location is a nonlinear state estimation in essence;the single observer passive tracking may form a unobservable system,makes the tracking filter instable and divergent.

• 利用角测量估计目标的距离和速度实质上是一个非线性状态估计问题,这种单站被动式跟踪可能构成一个不可观测系统,将导致跟踪滤波器的不稳定和发散。