When evaluating the shooting accuracy of underwater attack weapons against the surface target, we need to transform various coordinates into a unified coordinate. Typically, the surface target track uses the geodetic coordinate and underwater weapon trajectory uses the navigation coordinate. Therefore, trajectory data in the navigation coordinate need to be converted to the geodetic coordinate. Using an inertial measurement unit can only get the trajectory data in the navigation coordinate. Because of the Doppler effect, acoustic reverberation, range ambiguity, and low data refresh rate, the methods based on the cooperative acoustic beacon or the baseline positioning cannot meet the trajectory measurement requirements of the underwater high-speed attack weapon. In this paper, a method combining baseline positioning with an inertial measurement unit is proposed to solve the problem of trajectory measurement in the geodetic coordinate of the underwater high-speed weapons. The system composition, working principle, and measure results are introduced, and the measure errors are analyzed.
Testing and measurement are critical to the development, trial, and production of products. The trajectory parameters that can be obtained from underwater trajectory measurements include attitude angle, angular rate, velocity, displacement, ballistic inclination, ballistic deflection, tilt angle, angle of attack, and sideslip angle, for example. According to the data measured by the ballistic measurement system, the ballistic trajectory, ballistic dispersion, action characteristics, and performance of the weapon can be determined as an important basis for parameter optimization and design improvement during product development, and the underwater trajectory measurement process is extensive, difficult, and costly (Zhang et al., 2018). In the process of underwater highspeed attack weapon and surface target trajectory rendezvous testing, the trajectories of both are not measured in the same coordinate: underwater high-speed attack weapon ballistic data are obtained in the navigation coordinate, which is a customized coordinate based on the underwater vehicle, whereas the surface target trajectory is obtained in the geodetic coordinate. To evaluate the weapon and equipment performance, optimize the ballistic control algorithm, and determine the attack error, it is necessary to accurately measure the ballistic data of the underwater weapon in the geodetic coordinate. In this paper, a ballistic measurement method for underwater high-speed attack weapons in the geodetic coordinate is presented.