Observation coupling effect of attitude matching in transfer alignment for ship hull flexure measurement

Attitude Matching Method is commonly used in transfer alignment to calibrate coordinate of two spots in ship deck, and ship angular flexure is a transition variation of estimating attitude error. Attitude matching method based on local body framework is used to be measurement function in Kalman filter and dynamic flexure approximated a second-order Gaussian Markov stochastic process. But observation coupling effect caused by dynamic flexure and static flexure leads to inaccuracy results in optimal estimation. This observation coupling effect is not measured according to attitude matching method, and must evaluate it by means of angular velocity matching method. Simulations is done and validates this inference. The effect can result in inaccuracy evaluation of angular flexure, especially for static flexure. When ship maneuvers or swings by a wide margin, the effect can be weakened and get more accurate estimation of static flexure. So the precision of static flexure estimation by attitude matching measurement in Kalman filter is limited and needs other measurement information to assist it.