(This entry is a supplement for the entry concerning the Kim Okgyun's Korean map. )
The following is an excerpt of this page on the Tanaka Kunitaka's Takeshima site written in Japanese. The linked maps are also from the Tanaka's site.
Maps in the 19th century tended to print two islands on the eastern sea near the Korean peninsula. The two islands are both Ulleungdo. This duplication of Ulleungdo was caused by two independent findings of Ulleungdo by Westerners. Ulleungdo was initially found by a French, Lepaute Dagelet, and it was named "Dagelet" in 1787. An English explorer, James Colnett, also found Ulleungdo and named it "Argonaut" in 1789. Since Dagelet and Colnett assigned different latitude and longitude to "Dagelet" and "Argonaut", maps made by Westerners tended to print two islands in the area. Affected by these Western maps, Japanese map also tended to print Argonaut in addition to Ulleungdo on the eastern sea of Korea.
The followings are examples of the maps which printed the two Ulleungdo as "Dagelet"and "Argonaut".
Map I : Arrow Smith’s map published in 1811.
(Colnett’s ship, Argonaut, lost her rudder just after he found Ulleungdo. The description in the map "Argonaut lost her Rudder" indicates this incident.)
Map II : Thomson’s map published in 1815.
German Doctor Phillip von Siebold (1796-1866) who had lived in Japan for 5 years had the knowldge that there are two islands which Japanese call "Takeshima (Ulleungdo)" and "Matsushima (Liancourt Rocks)" between Korea and Oki islands. Thus he assigned these Japanese names to the two islands, "Argonaut" and "Dagelet", on his map. His map caused much confusion to both Japanese and Westerners since he assigned the Japanese names for Ulleungdo and the Liancourt Rocks to the duplicated Ulleungdo.
Map III : Siebold’s map published in 1840.
Liancourt Rocks were found by a French ship, Liancourt, in mid-19th century. The first Western map that described the Liancourt Rocks was published in 1849. Liancourt Rocks were also called Hornet Rocks, since English ship "Hornet" found these rocks in 1855. Thus, maps published in late-19th century tended to describe three islands, "Argonaut", "Dagelet" and "Liancourt (= Hornet)", between Korea and Oki islands (Okinoshima).
Map IV : Wilhelm Heine’s map published in 1855.
Map V : A map compiled by U.S. commodore Matthew Perry (published in 1856).
Note that Argonaut is labeled "nicht Vorhanden (not exist)" in the above maps. It had been known by this time that the longitude and latitude assigned to Ulleungdo (Argonaut) by Colnet was inaccurate and that there was no island at this map position.
These Western maps were imported into Japan. So Japanese maps affected by Western maps also describe three islands between Korea and the Oki islands.
Map VII : Katsu Kaishu’s map (大日本沿海略図 by 勝海舟) published in 1867.
Map VIII : Hashimoto Gyokuran’s map (大日本四神全図 by 橋本玉蘭) published in 1870.
In the above maps, the duplicated Ulleungdo (Argonaut and Dagelet) are labeled as Takeshima (竹嶋, 竹シマ) and Matsushima (松島, 松シマ), respectively, in accordance with Siebold’s map (Map III).
MAP X Japanese Navy Map published in 1881.
Ulleungdo is labeled as "Ulleungdo (Matsushima)" (鬱陵島 (松島)). Argonaut is not printed.
In short, Ulleungdo and the Liancourt Rocks were called "Takeshima" and "Matsushima", respectively, in Japan in premodern period, but these names were used for the name of duplicated Ulleungdo, Argonaut and Dagelet, in Western maps. Japanese government officially decided in 1905 to rename the Liancourt Rocks, which were formerly called Matsushima, "Takeshima", since the name "Matsushima" became popular as the name of Ulleungdo (= Dagelet).