The altitude of the sun, or the and of stars could be calculated with these by inputting the location of the observer on the ring of the globe.
Later events of Jang's life, including the date of his death, were not recorded.
ๅคงๅดๆญฃๆฌก, ใไธญๅใฎๆๅบงใฎ๏ฆๅฒใ, ้ๅฑฑ้ฃ, 1987.
If the earthly globe be turned, the hour-index goes round its hour-circle; but if the sphere be turned, the hour-circle goes round below the index.
Woongjin Wi-in Jeon-gi 11 Jang Yeong-sil Woongjin Publishing.
๊ฐํน, ํผ์ฒ์๋ฅผ ์๊ณ๋ผ๊ณ ์๊ฐํ๋ ์ฌ๋๋ค์ด ์๋ค.