We consider the problem of estimating the position of an object moving in the space by observing its image with the aid of a CCD camera. The problem can be converted into the observation of a dynamical system with nonlinearities. A new method is proposed to identify the obtained dynamical system. The attraction of the new method is that the algorithm is very simple and easy to be implemented, and it is robust to measurement noises. Further, minor a priori knowledge of the system is required in the new formulation. Simulation results show the superiority of the new method to the traditional ones.