The Angbu Ilgu Sundial

Also called: Angbuilgu, Scaphe sundial of Joseon

The angbu ilgu, a sundial shaped like a cauldron facing the sky, was set up by the roads of Hanyang so ordinary people could tell the time.

In the tenth month of 1434 Sejong had angbu ilgu placed by the Hyejeonggyo bridge and in front of Jongmyo shrine so that passers-by could read the time. The name means "a sundial like a cauldron looking up at the sky": a pointer aimed at the celestial pole stands inside a concave hemisphere, and the time is read from where its shadow falls.

Besides the hour lines, thirteen transverse lines mark the solar terms, so the length of the shadow also showed the season. For people who could not read, the hours were marked with pictures of the animal deities of the hours. It is said to have been made by Jang Yeong-sil, Yi Cheon and others. The sundials of Sejong’s time do not survive; the extant ones are later Joseon remakes designated Treasures. The water clock Jagyeongnu was made the same year.