This means the time delay between the transmitter and the receiver is larger than the time delay between them in the condition that the sound ray is straightaway, then positioning error is caused.

• 海洋中声速分布是不均匀的，因此由于折射效应，声音在海洋信道传播过程中其声线是弯曲的，声线弯曲意味着声信号从发射点到接收点的传播时延大于声信号直线传播的时延，致使定位产生误差。