The claim has been made upon the results that the wmt method should be used in the area near the vertical , while the phase difference method in slant beams and a rule has been given to select among those two methods according to the " effect value " on condition the depth is known for the consideration of improving the measurement precision , this paper studies the factors which affect the toa measurements , and three expressions of precision has been introduced as to applications of phase difference method , this paper introduces an automatic hunting method based on amplitude power to get the range of echo arrival 采用方差分析的方法,使用重復海試數據對wmt法和相位差法的優劣進行了分析,指出了垂直附近應該使用wmt法,而傾斜波束應該使用相位差法;給出了在深度真實值已知前提下wmt法和相位差法使用的判決準則,即根據效應值的大小來選擇。本文從提高測量精度角度出發,分析并驗證了影響toa測量精度的因素;給出了三種精度表示。在應用相位差法時,引入了一種基于幅度能量的區間自動搜索方法;實驗表明該方法能很好地確定回波到達的大概時間范圍。