An INS/GPS coupled system facilitates improved navigation with low-cost equipment. This system requires a navigation filter that produces an accurate estimation. The EKF(Extended Kalman Filter) estimates an optimal navigation solution. However, The EKF cannot estimate accurate values when non-linearity or initial error of the system is large. In this situation, the UKF(Unscented Kalman Filter) can substitute for the EKF. The UKF outputs better navigation solutions, because it applies an unscented transformation of sigma points. In this paper, implementation of an INS/GPS weakly coupled system simulator and comparison of nonlinear filters for the navigation system will be covered.

Keywords:  INS/GPS, EKF, UKF