Moreover, to renew our air supply, the submersible rose to the surface of the waves only at night, and relying solely on compass and log, it steered by dead reckoning.

并且，我们的船夜间才浮上水面来，调换新鲜空气，它单单根据罗盘的度数和测程器的指示来行驶。

Really the only option they had was to rely on something called dead reckoning, basically figuring out where you are by estimating your speed and compass heading to plot your journey.

实际上他们唯一的选择是依靠一种名为航位推算的方法，大体通过估计航速和指南针指向来确定你的位置，从而规划航程。