Japan and Korea are no longer disputing each other's claim to Ulleungdo since Japan conceded Ulleungdo to Korea in the 1690s, but the two countries are disputing over Liancourt Rocks, which are a small group of rock islets about ninety-two kilometers southeast of Korea's Ulleungdo and about 160 kilometers northwest of Japan's Oki Islands. Koreans call the rocks "Dokdo," and Japanese call them Takeshima (竹島), which was also the former Japanese name for Ulleungdo. The Jang Han-sang expedition to Ulleungdo in 1694 is significant in the Dokdo/Takeshima debate for a few reasons. One reason is that it seems to be the only time that Liancourt Rocks (Dokdo/Takeshima) was mentioned in Korean records. In the record, no name was given for Liancourt Rocks, but Jang Han-sang said that he saw, from a peak on Ulleungdo, an island in the distance, about 300 ri (120 kilometers) southeast of Ulleungdo. We know that he did not travel to Liancourt Rocks because he estimated the size of the island to be about one third the size of Ulleungdo; however, Ulleungdo is actually about 391 times bigger than Liancourt Rocks.
Another reason the Jang Han-sang expedition to Ulleungdo is significant in the Dokdo/Takeshima debate is that Jang Han-sang said that Ulleungdo was "the so-called Sambong" (此所謂 三峯), which was a reference to Sambongdo (三峯島). "Sambongdo" means "Island of Three Peaks." Koreans say that Sambongdo was one of the old names for "Dokdo" (Liancourt Rocks), but Jang Han-sang's report and other references to Sambongdo in Korean documents show that Sambongdo was just another name for Ulleungdo.
A third reason that the Jang Han-sang expedition is significant is that he reported seeing a small island about five ri (2 kilometers) off the east coast of Ulleungdo. He said that the island had groves of haejang bamboo (海長竹) on one side. The island he was talking about was almost certainly Ulleungdo's neighboring island of Jukdo, which is about 2.2 kilometers off Ulleungdo's east shore. The fact that he said the island had groves of haejang bamboo (海長竹 or 海藏竹) on it is also significant because haejang bamboo is a particular type of bamboo that can grow seven meters tall. On a 1711 map of Ulleungdo, made by Ulleungdo Inspector Bak Chang-seok (朴昌錫), there is a small island off the east coast of Ulleungdo labeled "Groves of Haejang Bamboo, the so-called Usando" (海長竹田, 所謂于山島). Koreans claim that Usando was the old Korean name for "Dokdo" (Liancourt Rocks), but Jang's 1711 maps shows that Usando could not have been Dokdo because Dokdo does not have the soil to grow "groves of haejang bamboo." Besides, Dokdo is ninety-two kilometers southeast of Ulleungdo, but Jang's map shows Usando just offshore of Ulleungdo.
Considered together, Jang Han-sang's 1694 expedition report and Bak Chang-seok's 1711 map make it quite clear that "Usando" was not Liancourt Rocks, but was, instead, an old name for Ulleungdo's neighboring island of Jukdo (竹島), which, by the way, does have bamboo growing on it.
Here is the relevant portion of Jang Han-sang's 1694 report (蔚陵島事蹟) and scans of Bak Chang-seok's 1711 map of Ulleungdo. Notice that in the center of the island on Bak's map, he drew three peaks (三峯) in a way that they stood out from the surrounding peaks. This is more evidence that Sambongdo (三峯島 - "Island of Three Peaks") was just another name for Ulleungdo.
Excerpt form the 1694 "Ulleungdo Sajeok" (蔚陵島事蹟)
About five ri to the east is one small island. It is not very big or very high, and it has a grove of haejang bamboo (海長竹) growing thickly on one side. On a day the rain clouds cleared and the fog settled, we went into the mountains and climbed the central peak. Two tall mountains to the north and south were facing us. This was the so-called Sambong (三峯 - "Three Peaks"). The winding shape of Daegwanryeon (大關嶺 - mountain range on the east coast of the Korean peninsula) was visible to the west. Looking toward the east, there was one island far off to the southeast. The size was only about one-third of Ulleungdo. It was only about 300 ri [120 kilometers] away.
동쪽으로 5리 (2킬로) 쯤에 한 작은 섬이 있는데, 고대(高大)하지 않으며 해장죽 (海長竹)이 한쪽면에 무더기로 자라고 있다. 비 개고 안개 가라앉는 날 산으로 들어가 중봉에 오르면 남북 양봉(兩峯)이 높다랗게 마주보고 있는데 이를 삼봉(三峯)이라고 한다. 서쪽을 바라보면 대관령의 구불구불한 모습이 보이고 동쪽을 바라보면 바다 가운데 한 섬이 보이는데 아득히 진방(辰方)에 위치하며 그 크기는 울도의 3분의 1 미만이고 (거리는) 삼백여 리에 불과하다.
東方五里許 有一小島 不甚高大 海長竹叢生於一面 霽雨?捲之日 入山登中峯 則南北兩峯 岌崇相面 此所謂三峯也 西望大關嶺逶迤之狀 東望海中有一島 杳在辰方 而其大滿蔚島三分之一 不過三百餘里.