Natural magnets were ground into crude compasses which called “Sinan” as early as in the Warring States Period, and that was the oldest compass in the world, 2000 years from now. The magnetic effect of Sinan was weak, as was its ability to guide south.
By the Song Dynasty, artificial magnets had been invented, whose magnetism was more stable than that of natural magnets. The equipment of the compass had been improved a lot and people invented several guiding tools such as the compass fish, the compass turtle, and the floating compass.
In the Song Dynasty, the maritime trade was prosperous. In order to overcome the difficulties of traveling in ocean, at the end of the Song Dynasty, compasses were used for navigation. There was even compass needles which was made by putting a compass on a dial with degree markings. This helped the sailors to find out the direction even during those days without sunlight and nights without moonlight.