Rain gauge

Joseon made the cheugugi rain gauge and installed it in the capital and every county to record rainfall systematically.

Before this, rainfall was gauged by how deep it had soaked into the soil, which varied with the ground and was unreliable. The crown prince, later King Munjong, worked on measuring rain caught in a vessel. In the fifth month of 1442 a standard size was fixed and gauges were placed at the Bureau of Astronomy in the capital and at provincial and county offices; after each rain the depth was measured with a standard ruler (jucheok) and reported. River levels were read from the Supyo gauge on the Cheonggyecheon. It is regarded as the world’s first rain gauge; the one that survives was made in 1837 for the Gongju provincial office.