Azimuth update without aircraft maneuvers in INS/GPS/EOS (electro-optical sensor) integrated systems

The INS/GPS/EOS integrated systems, intended for passive target location, enable one to estimate the target position to the accuracy, which is often limited by the INS azimuth error. Basically the INS azimuth can be updated by using GPS data, however such update requires exclusive aircraft maneuvers, which are not always feasible. In the INS/GPS/EOS integrated systems the INS azimuth can be updated without aircraft maneuvers by using the line-of-sight unit vector, measured while the aircraft passing over some stationary ground point and EOS locking at it. In this paper the updating measurement is defined, which enables to estimate the INS azimuth error by using the line-of sight unit vector to some ground point without estimating its position. The accuracy of the INS azimuth update by using this updating measurement while the regular straight-line flight is analyzed in comparison with the INS azimuth update by using GPS data during the exclusive circular maneuver.