repeatedly measuring a velocity difference between the carrier vehicle and the carried vehicle updating a state vector that include a predicted value of the velocity difference propagating the vector forward in time and moving the carrier vehicle and the carried vehicle along a trajectory application_number US 87167901 A description the preferred embodiments herein are not intended to be exhaustive and to limit in any way the scope of the invention rather they are used as examples for the clarification of the invention and for the enabling of other skilled in the art to utilize its teaching for a detailed description of the invention reference is now made to fig1 three sets of coordinates have to be considered the global llln navigation system 11 the body axes system of the carrier airplane not shown and the cartesian right hand coordinate set 12 which is computed by the ins of the carried vehicle according to its imu data while the ins of the carrier platform handles satisfactorily the difference between the first two coordinate systems uncertainties arise with respect to the alignment of the first and third coordinate systems as a result the computed coordinate set of the carried vehicle is rotated with respect to the llln system by a yaw angle u03c6 about the d axis with a pitch angle u03b8 about the e axis and a roll angle.