Up till 500 years ago, our ancestors still led advancements in fields of metallurgy, economics, mathematics, nautical navigation, ceramics and silk.

直至500多年前，我们的祖先还在冶炼、经济、数学、航海、陶瓷、丝织等诸多方面引领着这个世界。

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In normal coastal navigation, positions should be fixed every 15 minutes and plotted on the nautical chart.

正常沿岸航行应15分钟确定一次船位并在海图上划出。

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