By the Northern Song period, Chinese writers described practical ways to use magnetism to find direction. These early devices mattered because they created a bridge from earlier land-based direction tools to instruments that could later support longer sea travel.
The military compendium Wujing Zongyao (written around 1040–1044) described a thin iron “fish” that could be heated, cooled, and then floated on water to indicate direction. This is important because it shows a clearly documented, practical magnetic direction-finder in 11th-century China.
In 1088, Shen Kuo’s Dream Pool Essays described magnetizing steel needles with lodestone and discussed why a needle may not point exactly to true north (magnetic declination). This strengthened navigation by moving from rough direction-finding toward more accurate, repeatable readings.
Zhu Yu’s Pingzhou Table Talks (published in 1119) described ship pilots using a “south-pointing needle” in dark weather, alongside the sun, stars, and coastal knowledge. This is a key step because it documents the compass as a working maritime tool, not only a land or scholarly instrument.
Over time, Chinese “rutters” (written sailing directions) increasingly used compass directions to guide travel across open water. This mattered because it connected a physical instrument (the compass) to a written system for repeating routes more reliably.
Song-era writers described moving beyond simple cardinal directions toward a more finely divided directional system, making it easier to record and follow headings at sea. More precise headings helped sailors translate observations and experience into instructions that others could use.
By later imperial periods, Chinese sailing directions evolved from mainly descriptive guidance to more quantitative guidance, and then to guidance supported by charts. The compass was central to this shift because it provided a standard way to state course directions across different voyages.
During the early 1400s, the Ming court sponsored long-distance maritime expeditions associated with Zheng He. These voyages depended on coordinated navigation over long stretches of ocean, where compass-based headings were useful when stars, sun, or coastlines were hard to use.
A major collection of nautical charts linked to Zheng He’s era—often referred to as Zheng He Hang Hai Tu—is described as being compiled in the first half of the 15th century. These charts reflect a navigational world where routes could be communicated using consistent directional information, including compass-based bearings.
From the 11th through the 16th centuries, Chinese sailors and writers increasingly treated the magnetic compass as part of a larger navigational toolkit (alongside stars, sun, soundings, and route knowledge). The lasting outcome was a more standardized way to record and share sea routes, strengthening long-distance travel and the transmission of nautical knowledge over generations.
In 1621, Mao Yuanyi compiled the Wubei Zhi (Treatise on Military Preparedness), a large military encyclopedia that included naval material. This compilation mattered for the compass story because it helped preserve earlier maritime route knowledge and chart traditions in printed form.
In 1628, Wubei Zhi was published, including the navigation charts now commonly called the Mao Kun map. The charts are significant because they show routes and sailing instructions in a format that later readers could study, copy, and discuss—supporting the long-term legacy of compass-aided navigation.
Use of the magnetic compass in Chinese navigation (11th–16th centuries)