早期欧洲的探险者是沿着海岸线的陆标,在茫茫大海上探寻航路的。然而一旦船只航行到看不见陆地的地方,他们就需要更可靠的航海技术了。航海术就是:驾驶船只经最佳航线,从一地航行到另一地的技术。中世纪的航海家发现:通过观察北极星的位置和太阳的运转,可以测出船只所在的南北位置。随着中国指南针航海技术的传入,十五世纪成了欧洲人海洋探险的伟大时代,航海家发明了一些导航的仪器。例如,罗盘能使船只按固定航线航行,观测仪或四分仪能测定船只的位置。这类工具最初都很简陋且不够精确,但是随着航海活动日益普及,航海仪器也就越来越精良了。 Explorers of early Europe are landmarks along the coastline, in the vast sea to explore the route. Once ships sailed to invisible places, however, they needed more reliable nautical techniques. Nautical technique is the technique of navigating from one place to another by driving the best way for ships. Medieval navigators discovered that by observing the location of the Polaris and the operation of the sun, the north-south position of the vessel can be measured. With the advent of Chinese compass navigation technology, the fifteenth century became a great era for European exploration of the sea. Navigators invented some navigational instruments. For example, a compass can make a ship sailing on a fixed route, and an observer or a tetrapod can determine the position of the vessel. Such tools were crude and inaccurate at first, but as navigation became more pervasive, navigation instruments became more sophisticated.