Abstract: A weapon system comprising a mobile platform (1) e.g. an aircraft incorporating a first three-axis attitude reference sub-system (13), and a guidable vehicle (3) launchable from the platform (1) and incorporating a guidance sub-system (15) incorporating gyros (17) wherein correction of gyro parameters, i.e. scale factor and zero offset, of the vehicle attitude reference sub-system (15) is effected prior to launch of the vehicle (3) on the basis of repetitive comparisons of attitude data as measured by the platform and vehicle sub-systems (13, 15). The vehicle (3) may comprise a dispenser of a number of munitions (5) each itself incorporating a guidance sub-system (25) incorporating gyros (27), in which case corrections of gyro parameters of the missile guidance sub-system (25) may be effected prior to missile launch on the basis of repetitive comparisons of attitude data as measured by the dispenser and munition sub-systems (15, 25).

Abstract: A strapped-down intertial system for a vehicle including computational means and a sensor package. The sensor package includes a first part (1) fixedly mounted on the vehicle, and a second part (5) which is rotatable about a first axis (Z). On the second part (5) are fixedly mounted gyroscopic means (13, 15) responsive to rotation about two axes, one of which is the first axis (Z), and accelerometer means (9, 11) responsive to acceleration along two axes, one of which is not the same as either of the two axes of the gyroscopic means (13, 15). The computational means is arranged to calculate the heading of the vehicle from the outputs of the gyroscopic means and accelerometer means taken with the first part (1) stationary, and the second part (5) successively in at least three different angular positions about the first axis (Z).