Abstract: A low cost shipboard reference system for carrying out the rapid alignment of aircraft inertial platforms in which an aircraft quality inertial reference is installed on shipboard and is operated in conjunction with a shipboard Kalman filter providing updating information thereto with the update connection from the Kalman to the shipboard inertial system normally kept opened and always kept opened during aircraft platform alignment to result in reference outputs for use in the aircraft system which are free of correlated noise but of sufficient accuracy for rapid alignment with a small azimuth error.