VOA慢速英语:The Centuries-Long Journey to the Discovery of Longitude

1.When people began sailing out of sight of land, sailors did not know how to tell where they were on the open sea.

out of sight看不见, 在视野之外

例句：We waved until the car was out of sight.
      我们一直在挥手道别, 直到汽车看不见为止。

2.Land travelers can look at a mountain, or a river, or an object that shows them where they are in relation to where they came from.

in relation to与…有关

例句：I have a lot to say in relation to that affair.
      关于那件事, 我有很多话要讲。

      The project was outlined with relation to available funds.
      这方案是根据可以获得的经费而拟定的。