The invention relates to an improved Inertial Navigation System (INS), which comprises: (a) an INS unit which comprises (a.1) an IMU which in turn comprises a set of at least three gyros and at least three accelerometers, all mounted on a rotatable stage; and (a.2) an INS algorithm for measuring the behavior of said gyros and said accelerometers during a mission, and calculating a navigation solution based on said measurements; and (b) a north finding determination unit, which comprises: (b.1) one or more from said IMU gyros and one or more from said IMU accelerometers; and (b.2) a north finding algorithm which utilizes measurements from said one or more north finding gyros and one or more north finding accelerometers during an initial conditions stationary state in which the stage is positioned in at least two separate stationary orientations, said north finding algorithm determines a north finding solution which is provided to the INS unit for initializing its said INS algorithm.