We studied the hour-lines of six extant Yangcheon-cheoks in Korea. To find whether Yangcheon-cheok was used in the whole area of Korea, we calculated the length of shadows of Yangcheon-cheok on the Korean Peninsula, Nanjing and Beijing as well as Hanyang (Seoul), according to 24 solar terms. Comparing the length of shadows with hour-lines of those relics, we could find that Yangcheon-cheok was suitable for use at limited times (from 9:00 to 15:00) during the year. Also, this sundial is more appropriate for use at low latitudes than high ones. Among existing relics, that of Seoul Museum of History made with porcelain was much more suitable to use at Hanyang and its higher latitude. Lee’s collection was also suitable to use at Nanjing. It is certain that Yangcheon-cheok was a portable sundial which could be used from nine to fifteen of clock all the year around except for the winter season.

• Sang Hyuk Kim(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea, Korea University of Science & Technology, Daejeon 34113, Korea) Corresponding Author
• Byeong-Hee Mihn(Korea Astronomy and Space Science Institute, Daejeon 34055, Korea, Korea University of Science & Technology, Daejeon 34113, Korea)
• Yong Sam Lee(Department of Astronomy and Space Science, Chungbuk National University, Cheongju 28644, Korea)