A table look-up method of sound ray correction

In underwater acoustic positioning system by using time-delays estimation, sound rays often propagate along curves because of the sound velocity varying with depth. A table look-up method is established to correct the bending of sound rays for a better positioning accuracy. From the ray theory, the horizontal distance and the time of sound propagation are the function of initial grazing angles. If the source depth, receive depth and sound velocity are known, the time of sound propagation can be determined corresponding to every initial grazing angle. A table look-up method is established for the correction of sound ray by building up a relationship between the horizontal distance and the time of sound propagation. Target’s Location can be calculated by intersecting circle radius, which is the shadow of sound ray, instead of using bending sound rays. Computer simulation and sea trial show that the correction is effective for increasing positioning accuracy under the complex hydrological condition.