Abstract: Position and orientation system (POS) has been used widely to compensate for the motional error of an airborne synthetic aperture radar (SAR),and its navigation precision has a direct effect on SAR imaging. In order to obtain higher navigating precision and numerical stability,an algorithm of Rauch-Tung-Striebel (R-T-S) optimal fixed interval smoothing based on singular value decomposition (SVD) was used in POS. The smoothed best estimate of position,velocity and attitude can be obtained by forwardpass Kalman filter(KF)based SVD and backwardpass R-T-S optimal fixed interval smoothing based SVD. This method not only has excellent numerical stability but also eliminates the necessity of system transition matrix inversion. The semiphysical simulation results show that this method has better precision and data smoothness than the KF currently in engineering application,and it may be an effective method for POS postprocessing.

Key words: position and orientation system, singular value decomposition, optional smoothing algorithm, synthetic aperture radar, motion compensation