The description landing on Dagelet,H.M.S Actaeon ,1859.

Dagelet Island Chart ,H.M.S Actaeon's survery (UKHO Ref:D7467)

There are Boussole Rock(Jukdo) and Seal Point(south Cape) on H.M.S Actaeon's chart of Dagelet 1859. (UKHO Ref: D7467). Also description of "Sea of Japan"

And U.K Hydro office replied as follows;
I have located the survey conducted by HMS Actaeon in 1859 of Dagelet Island (UKHO Ref: D7467), low resolution images attached, and reviewed several Sailing Directions including the China Pilot first edition (1855); second edition (1858), third edition (1861) and fourth edition (1864). It would appear that details from HMS Actaeon's work are not included until the 1864 Edition.

The description in the secondary source, by Blankey William about landing on Dagelet Island , H.M.S Actaeon .1859.
(quote from; On the coast of Cathay and Gipango forty years ago, A record of surveying service in the China Yellow and Japan Seas and the seabord of Korea and Manchuria,
Blakeney, William, R.N 1902.)

(P191 http://www.archive.org/stream/oncoastscathaya00blakgoog#page/n244/mode/2up)
"The Actaeon have to for a few hours off Dagelet Island, which emerges in solitary grandeur from the floor(2.000 feet deep) of the Japanse Sea, and rises to 4,000 feet above it. It lies 100 miles distant from the mainland of Korea, is clothed with forest from the verge of perpendicular cliffs of 500 feet, and is 20 miles in circumference. On every side were herds of seals, filling the air with sorrowful sounding cries, perhaps from terror at our appearing. We could make no headway through the dense undergrowth. La Perouse discovered this island in 1786, but there is no record of his landing.
A few half-starved Korean fisherman were collecting sea-slugs, etc., for Chinese epicureans, but had only a ramshackleold junk in which to make the passage across a stormy sea in almost perpetual fog. A weild and lonely spot is Dagelet Island.

By the way the book was published on 1902, They use "Korea Strait and Sea of Japan"
See Page 160 for name of the chapter;http://www.archive.org/stream/oncoastscathaya00blakgoog#page/n208/mode/2up

,attached map 1 -p167.
attached map2-p346

Sea of Japan
Strait of Korea
China Sea


1901-12.Papers on Mollusca of Japan

Papers on Mollusca of Japan (1901-12) by Pilsbry, Henry Augustus, b. 1862

Proceedings of the academy of Dagelet Island Now Known as Matsu-shima. A small and little-known island , in the Sea of Japan , east of Corea. See Travels, p.174 Adams visited the island, which is inhabited or at least used as a Haliotis-fishing station by Coreans, on the 28th of June, 1859. It is densely wooded, with a central peak 4,000 feet high. In the Travels, p. 178, a slug "with the mantle covering the whole of its back"(probably Philomycus) and a Zua (Coehlieopa) are mentioned.
In the paper on Japanese Helieidae only two species are given ;
Helix (Camcena) luchuana Sowb. (?).
Helix (Patula) elatior A. Ad.
It is the only locality for the latter species. The identification of H. luhuana is doubtful.

1882.Un Touriste Dans L'extreme Orient

Un Touriste Dans L'extreme Orient 1882
Japon, Chine, Indo-chine et Tonkin (4 Aout 1881-24 Jannier 1882)
Edmondo Cotteau
(PDF P6)
Le 6 aout, nous apercevons a tribord la cote de Coree, sous la forme de haules collines ideues, trop eloignees pour qu'on puisse en distinguer les details.Nous passons beaucoup plus pres, a habord, de la petite ile Dagelet. Il y a quelques annees, un bateau danois y fit naufrage; son equipage pat se refngier sur L'ile Argonaute, indiquee dans ces parages par les anciennes cartes anglaises, n'existe pas


1590-1592. Ignacio Moreira visit Japan

There are the description of "Sea of Japan" in the Historia de las cosas más notables, ritos y costumbres del gran reyno de la China ,published by Juan Gonzalez de Mendoza.Second devision Volume 3 was written by Martin Ignacio de Loyola. He did quoted the report about Japan by Ignacio Moreira who visit Japan during 1590-1592 and met Alexandro Valignano during his stay in Japan. Though Ignassio Moreira's Map of Japan is no longer exist, there are many Japanese map based on the information and design by Ignacio Moreira in Europe,e.g. Luis Teixeira and Dudley's map and so on.
said that

(ゴンザレス・メンドーサ シナ大王国誌 大航海時代 書Ⅶ 岩波書店 P540)
(Later I will put original description)

1880.A Forbidden Land: Voyages to the Corea

A Forbidden Land: Voyages to the Corea (1880)
Ernst Jacob Oppert , Ernst Oppert

Dagelet Description;
The third of the large islands lies on the east coast, about forty-five miles distant from the main land, under the 37-25 north lat, and 133-16 long. East, and is called Ollon-to by the natives. On several charts it is erroneously put down as belonging to Japan, which is not the case; generally it is marked Matsushima, while the French give it the name of Dagelet, and the Russians Dagette. It is nearly round, is about twenty-five miles in circumference, but of its interior very little is know to us on account of its steep and rocky approaches and inaccessible shores. Ollon-to is very celebrated in Corea for its great fertility; it is said to produce everything of excellent quality, and of a size so uncommonly large and almost gigantic, that the natives on the continent have finally concluded, and state it as their positive conviction, that and island rearing produce so extraordinary cannot be inhabited by common human beings, but must necessarily be peopled by a race of similarly gigantic size. To compare the farco, the goverment has actually issued a stringent prohibition against people from the mainland settling on the island, to avert any danger which might arise to the mother-coutry from the proximity of such a giant race! An official, with and escort, is indeed sent to Ollon-to from time to time, to see that this order is not violated, and to bring back as much of the produce as can be collected during his short stay there. Coreans of a sceptical turn of mind, however, affirm, and with some show of reason, that there are a good many settlers there in spite of the prohibition, who hide themselves in the woods on the approach of the commission of inspection, which, on its part, does not venture to pursue and capture the fugitives on account of the rumours prevailing.

*Notice "37-25 north lat, and 133-16 long " is french longtitude and calculate for U.K GMT to 37-25 north lat, and 130.56 long on GMT (-2°20' difference between Grinidge and paris)

1882.Corea, the hermit nation. Dagelet can be visible from Corean peninsula.

Corea, the hermit nation. I. Ancient and mediaeval history. II. Political and social Corea. III. Modern and recent history (1882)

by Griffis, William Elliot, 1843-1928

From a point on the sea-coast nearby, in fair weather, the island cone of Dagelet is visible.

Deer are very plentiful, and the best hartshorn for the pharmacy of China comes from these parts. Out in the sea, abut a degree and a half from the coart, lies and island, called by the Japanese Matsushima, or Pine Island, by the Coreans U-lon-to, and by Europeans, Dagelet, This island was first discovered by the French navigator, La Perouse, in June, 1787. In honor of an astronomer, it was named Dagelet Island. "It is very sttep, but covered with fine trees from the sea-shore to the summit. A rampart of bare rock, nearly as perpendicular as a wall. completely surrounds it, except seven sandy little coves at which it is possible to land." The grand central peak towers four sousand feet into the clouds. Firs, sycamores, and juniper trees around. Sea-bears and seals live in the water, and the few poor Coreans who inhabit the island dry the flesh of the seals and large quantities of petrels and haliotis, or sea-ears, for the markets or the main land. The island is occationally visited by Japanese junks and foreign whaling ships, as whales are plentiful in the surrounding waters. The Japanse obtained the timber for the public and other building at their new setlement at Gansan from this island.

It was during the summer of this year, 1787, that La Perouse sailed along the eastern coast of Cho-sen, discovered the straits which bear his name, between yezo and Saghalin, demonstrated that the Gulf of Tartary divided Saghain from the Asian mainland, and that Corea was not sea-girt, and named Dagelet Island and its comparison Boussole. He had a copy of Hamel's book with him. He noticed that signal-fires along the coast, which from headland to headland, telegraphed to the capital the news of the stranger with his "black ship". Not as yet, however, as afterward, did the government connect the appernce of European vessels with the activity of the Christians within the realm, although La Perouse sailed under the flag which eveer afterward was indissolubly associated in Crean minds with Christianity

H.M.S Samarang's discovery tour on Sea of Japan, landing on Dagelet.

The description landing on Dagelet by Arthor Adams with H.M.S Samarang. 1846-49, discovery tour around Sea of Japan.
From ; Arthor Adams, Travels of a naturalist in Japan and Manchuria (1870) page 174-178.

We proceeded next to Dagelet Island where we arrived on the 28th June, at which period the weather was in every way favourable for its examination. It is one of the discoveries of La Perouse, and named after the astronomer of the Astrolabe. As we pulled towards the island I found the description of the renowned navigator very exact. “Very steep,” as he says, “but covered with fine trees from the sea-shore to the summit. A rampart of bare rock nearly as perpendicular as a wall completely surrouds it, except seven little sandy coves at which it is possible to land.”
We saw the grand central peak towering four thousand feet above us, partially enveloped in clouds. Around its base were huge, detached rocks, some of them four or five hundred feet high, one resembling a sugar-loaf, and another a rude arch. Within a little distance from the shore, numbers of sea-bears, of a reddish-brown colour, came up repeatedly and barked around the boat. The mad pranks and uproarious conduct of these strange ursine creatures offered a striking contrast to the placid demeanour of the gentle Phocae, or common seals, which only raised their round hears above the water, wounderingly gazed around, and quitly sank again below the surface. Shoals of black-fish rose up further off, baring their dark rouded backs; while several right-whales were spouting in the far distance. Some flying-fish leapt from the water, pursued by a large fish of the mackerel tribe, a noticeable fact,- four seals and flying-fish are not usually seen together. As we neared the island the wave-beaten limestone barrier, weather-stained and variegated with encrusting lichens, towered up from the surface of the sea, crowned with fit-trees, sycamores, and junipers. The officers of the “Boussole” in La Perouse’s voyage did not land, and we were probably the first Europeans who had ever set foot on the island.
The shore is composed of great limestone boulders, worn round by the action of the waves; the tidal rocks are covered with barnacles and limpets; and I observed that Monodonta neritoides, had taken the place of M. Labeo, which is the common species on the mainland. The barnacles are Pollicipes and Conia, and the Littorina or periwinkle is similar to that of the mainland.
As we landed in a little bay we perceived three poor Koreans at work. We observed that they were engaged with adze and saw in repairing a dilapidated boat exactly as La Perouse found those he saw eighty years ago. They had dried vast nnumbers of haliotis or sea-ears, which they string upon rattans for the Chinese market, and sell at the rate of three hundred for a dollar. They likewise collect great heaps of dried seals’ flesh, near which I found a dermaster, a silpha, a nitidula, and a staphylinus,-all carrion-beetles.
We made our way into the densely-wooded interior by means of the dried-up watercourses, which form steep, rough paths among the trees. Fringing the shore were gigantic Archangelicae, on the milk-white umbels of which flies, beetles, and bees were numerous. A species of Cissus was trailing over the great round boulders, and here and there was a vinic loaded with bunches of small sour grapes. The common thyme and Scrophularia, a little yellow Sedum, and a large blue aster, enlivened the edges of the rocks. The wood was composed of sycamores and junipers, with the Sambucus japonicus, the berries of which are red and not black, as in the common elder. I was curious about the denizens of so small and isolated an island. The birds I observed were cormorants, hawks, gulls, pigeons, blackbirds, sparrows, and small birds like willow-wrens. The Korean fisherman dry large quantities of petrels, leaving their skins in mouldering heaps along the shore. The only indication of a manual I met with was the skull of a cat, which may have belonged either to a wild species from the mountainous interior of the island, or to a domestic animal wrecked in a junk. I found among molluses the very peculiar slug of the mainland, a creature with the mantle covering the whole of its back; a little shining land-shell, named Zua, and two species of snails. The only reptile I noticed was a small snake coiled up under a stone. Under the dead fallen leaves and flat stones, I found a centipede about four inches in length; besides two kings of “thousand-legs.” And a large, brown wood-louse, called Armadillidium by naturalists. As for the beetles, they were too numerous to mentin. We enjoyed a refectin in a small secluded cove, and them pulled partly round the island, admiring many rocky pinnacles and off-lying rugged arches, and then rejoined the ship, which was standing off and waiting for the boat.


1813.Voyage round the world.1813. K.v Krusenstern

129 Kruzenshtern, Ivan Fedorovich (1770-1846)
Voyage round the world.1813.

VOL. I. xxxii, [11], 314 p., [2] leaves of plates. 27 cm.
VOL. II. 404 p., [1] leaf of plates.

The Nadeshda quits Nangasaky―Measures of Precaution adopted by the Japanese Government with respect to our Voyage to Kamtschatka―Plan of Operations for the Year―Stormy Passage round the Gotto Islands―Description of Colnett and Tsus-sima―Observations on the Longitude of Tsus-sima―Important Errors in the Chart of La Perouse's Voyage between Manilla and Kamtschatka―We perceive the Coast of Japan―Suppose the Land we see to be the Island called Oki―Remarks upon the Variation of the Compass and State of the Barometer in the Japanese Sea―We explore the North-west Coast of Japan―Discover the Straits of Sangar―Astronomical Situation of the two Capes in the Islands of Nipon and Jesso, which form the Western Entrance of the Straits of Sangar―Examination of the West Coast of Jesso or Matzumay―We explore Gulf Strogonoff, and are disappointed in our Hopes of finding here the Passage which separates the Islands of Jesso and Karafuto―We discover that La Perouse's Peak de Langle and Cape Guibert are not situated in Jesso, but upon two different Islands―We sail between these and the North-west Coast of Jesso―Find ourselves in the Straits of La Perouse―Anchor at the Northern Point of Jesso in a Bay, which obtains the Name of the Count Romanzoff.p. [1]-43.


1787.Jean François de Galaup, comte de La Pérouse first survey at Detroit de Coree and Dagelet,

日本海北西部朝鮮沿岸や、北東部Tataristanの地理情報は、世界航海が盛んになり始めても、1780年代になっても結局残されたままだった。La Perouseが日本海Mer Du Japon海域を探検し、朝鮮海峡Detroit de Coreeを測量し、これらの情報は、朝鮮半島東沿岸部を探検測量した英国のBroughtonや、ロシアのKrusesternなど"日本海”の探検家へと引き継がれる。これが契機で1730-1770年頃まで一時的に増えていた朝鮮海の記載が急減する一方で、朝鮮海峡の名称が新たに登場し、更に日本海が圧倒的多数に成ったのである。また、この後Broughtonの朝鮮東海岸の測量によってフランスなどの地圖にはBroughton Bayの附近にMer Du Coree(後のBroughton Bay, 現在のEast Korean Gulf)が記載される事となる。

Refernced from ;La Perouse 太平洋周航記 下 佐藤淳二訳 第十五章 カビナテ出航、台湾・朝鮮海峡から日本海へ

能登岬の測定によってラ・ペルーズは、この海域の水路測量のために大きな貢献をしたのである。なぜなら、朝鮮や沿海州沿岸との関係における日本の位置 は、これによってかなり画定されることになったからである。彼らは次のように言っている。「大多数の読者にとって、まさに不毛と思われるこの短い鑑札のた めに、我々は濃霧おなかでの困難な十日間の航海を要したのだった。地理学者たちは、われわれがこの時間をよく利用したと考えるだろうが、ただわれわれの広 大な計画が、この沿岸、ことにこの国と朝鮮とを判っている海峡の芯の形を記述するtことが出来たと思われる南へ見勝手いくつかの地点を、調査士かつ測定す ることが許されなったことを遺憾におもうであろう。」、
Refernced from ;Philip von Sebold ”Japan" Vol1 第四章 ヨーロッパ人による日本とその海域発見の歴史的概観 P81

"...May 27th I gave the signal that we arrived on the East Sea. After a short while, to the North~Northeast an island was observed that was not on any charts. This island seemed to be 20 leagues (actual 137kms) away from the Chosun coast. I tried to approach the island but it was difficult because the island was is the same direction as the winds. Fortunately, during the night the direction of the wind had changed. (May 28th) By dawn we left toward the island for measurements and I decided to name this island Dagelet after the astronomer Lapaute Dagelet among our crew who sighted it first. The circumference of the island is only three leagues (actual 33kms) Maintaining a distance of 1.9kms from the island we travelled almost all around but failed to find deep water. Therefore I decided to lower a small boat into the water and left Boutin in command to check the depths of water en route to land. He soon found that the depth of this place was 140 meters and it was about 200 meters from the island. The Northeast point of the island is 37° 25' North latitude and the 129° 2' East longitude. Even though the island is made of sheer cliffs, from the top to the shore it is covered with very beautiful trees. Other that seven little inlets for mooring the island is surrounded by precipitous cliffs. In this little inlet we observed some boats of Chinese style being built. It appeared that those boat builders were startled by our ship maybe because they were within the range of our cannons. They fled into the woods about 50 paces from their workplace. However, what we saw was a few huts, with no village or crops. It appeared that some Chosun carpenters from the mainland which is only 110 kms from Dagelet come with provisions and build boats during the summer before they take them to the mainland for sale. I'm sure this assumption is correct. When we returned to the West point of the island we again observed other workers building boats but they didn't see us approach because a point of land blocked their view. Those people by a tree stump looked frightened to see us except for a couple of them who didn't seemed to be afraid of us, they all ran into the woods. I thought we needed to persuade them that we are good people and are not their enemy so I looked for a place to drop anchor. Unfortunately the strong currents pushed us away from the island. Night approached. Due to our concerns that we might again be pushed from the island, and fears of not being able to retrieve the dispatched boat under Boutin's command I signalled to M. Boutin, who was about to land, and ordered him to return. I ordered the Astrolobe which was far to the West due to currents, to approach Mr Boutin's group. Luckily the high peaks of Dagelet blocked the winds and spend the night peacefully...."
27日、船首を風下の東に向けるよう合図したが、まもなく北北西に海図にない島を認めた。朝鮮半島から約20リユくらい沖合いであった。島に接近しようと試みたが、島へと風が吹つけていたので接近は無理だった。しかし夜のうちに風向きも変わり、空が白む頃にはこの島を偵察するべく船首を向けた。この島を最初に発見した天文学者であるダジュレ氏にちなんで、ダジュレ島と命名した。島は周囲僅かに三リユ、海岸線に沿って進み、ほとんど一周したが、三分の一リユまでせっきんしても海底を測深できなかった。そこでボートを降ろし岸辺まで測深させることを決断、ボートの指揮をブタン氏にとらせた。彼の報告では、海岸に打ち寄せるうねりが始まるあたり、島の岸から100トワーズの距離でやっと20ブラスの水深を測ることができたという。島の北東端は、緯度三十七度二十五分、パリ子午線緯度百二十九度二分であった。島は、一周三リユほどであろうか、切り立った海岸であったが、頂上から海面附近まで眼も覚めるような美しい樹木で覆われていた。剥き出しの岩壁が、殆ど城壁のように垂直に 立して島をぐるりと取り巻いていたが、例外として七箇所の砂浜の小さな入り江があり、そこは上陸可能であった。この入り江にみつけた作業場には、中国船とまったく同一の形状の船がいくつか建造中であった。艦載砲の射程距離内に私達の艦艇が現れるや、職人達は仰天したのか、作業場から五十歩と離れていない森の茂みの中に逃げ込んでいった。それとは別に、小屋がいくつか見受けられはしたものの、集落も耕作地も無かった。つまり、一番ありえそうな推論は、次のようになる。即ち、二十リユばかりしか離れていない朝鮮半島から船大工たちが渡ってきて、ここで作った船を朝鮮各地で売るのだろう、と。これは最初は憶測だったが、しかし次第に確信に変わっていった。というのは、西側の岬を回りこんだ際に、ここにもさらに作業場があって、それまで岬に隠れて見えなかったわが艦艇が突然姿を現したものだから、浜の職人たちがびっくりして森に転がるように逃げていくのを目撃したらだった。私たちを見ても平然として後に残っていたのは、せいぜい二、三人であった。停泊できる場所を見つけて友好の態度を示し、是非とも私たちが敵でないことを納得させたかったのだが、しかし激しい潮流によって船は岸から引き離されたのだった。周囲は夜の帳が下りようとしていたので、ボートに帰還を命じざるを得なかった。ブタン氏は上陸目前であったが、船が風下に流されてボートが改修できなくなる事を私は強く懸念したからである。潮流にながされてずっと西にまで進んでいたアストロラブ号にようやく追いつく頃には、凪の静かな夜となった。ダジュレ島にXえる山々が、沖合いからの突風を遮ってくれるおかげだった。
Refernced from ;La Perouse 太平洋周航記 下 佐藤淳二訳 第十五章 カビナテ出航、台湾・朝鮮海峡から日本海へ

Refernced from ;Philip von Sebold ”Japan" Vol1 第四章 ヨーロッパ人による日本とその海域発見の歴史的概観 P80-81

・Chart by La Perouse
   Mers, Chine, Tartarie. La Perouse, Jean-Francois de Galaup, comte de, 1741-1788, 1797
   Plan de Eile Dagelet 鬱陵島

Maps by Sebold collection .(requires Djvu Installation)


Timeline for explorer and survery ,sailing magazine around Sea of Japan

Timeline for explorer and survery ,sailing magazine around Sea of Japan
1643. Holland Fleese's survery around northern part of Japan,(Not sure into sea of Japan area)
(His map)
1785-1797 Jean François de Galaup, comte de La Pérouse world discovery tour, through Sea of Japan.
1787.05.Found Dagelet(Ulluengdo/) on Mer du Japon.
1789.10 James Colnett found Argonaut island (it is ghost of Dagelet, 129"E, wrong measurement result)
1796.Broughton, Willam Robert explored east coast of Korea.
1803-1806.Adam Johann Ritter von Krusenstern''s world discovery tour, through Sea of Japan.
1810. Adam Johann Ritter von Krusenstern's Publication of "Reise um die Welt in den Jahren 1803, 1804, 1805 und 1806 auf Befehl Seiner Kaiserliche Majestät Alexanders des Ersten auf den Schiffen Nadeschda und Newa"
1823-1829 Philipp Franz Balthasar von Siebold visiting Japan for study
Philipp Franz Balthasar von Siebold "Japan" publication 1832-1851
1848.Chelokee's sailing around Sea of Japan, "discovered" Liacnourt Rocks
1849.Liacnourt 'sailing around Sea of Japan, "discovered" Liacnourt Rocks
1849.Cambria's sailing around Sea of Japan , found Liacnourt Rocks
1852.Capricieuse's sailing around Sea of Japan
1853 Nagasaki Naval Training school open.
1854.Pallda/Pallas's survey around Sea of Japan, found Oribitsu/Melenei Rocks(Liacnourt Rocks)
1855.China Pilot 1st Edition.
by Loney, R
1855.Hornet sailing around Sea of Japan, found Hornet Rocks(Liancourt Rocks)
1856.Commandar Mattew C Perry squadom to Japan
1858.Commander Ward survey (Actaeon).
1858.China Pilot," 2nd Edition (1858)
by King, J. W. Great Britain Hydrographic Dept
1860.Renseignements hydrographiques sur les îles Bashée, les îles Formose et Lou-Tchou, la Corée, la Mer du Japon, les îles du Japon (Ports d'Hakodaki, Ne-e-Gate, ... Yedo) et la Mer d'Okhotsk (French Edition) (Paperback)
by Paul Dupont, Paris.
1861. China Pilot Vol3
by King, J. W. Great Britain Hydrographic Dept
1864.China Pilot Vol4
by King, J. W. Great Britain Hydrographic Dept
1867.The China Sea Directory (1867)
John William Reed , John William King , Great Britain Hydrographic Dept
1867.Pilote de la mer de Chine, Ve Partie, La Mer du Japon. Paris
1871 Japan's Maritime survey department open 水路局
1873.China Sea Directory," 1st Edition Vol. 4 (1873)
by Jarrad, F. W,Great Britain Hydrographic Dept
1875.The navigation of the Pacific Ocean, China seas, etc. (1875)
by Labrosse, F
1878.A directory for the navigation of the Indian Archipelago, China, and Japan, from the straits of Malacca and Sunda, and the passages east of Java. To Canton, Shanghai, the Yellow Sea, and Japan, with descriptions of the winds, monsoons, and currents, and general instructions for the various channels, harbours, etc (1878)
by Findlay, Alexander George, 1812-1875
1880.Battle ship Amagi's survey on Ullueungdo
1884.China Sea Directory vol. 4 (Second Edition). London
by Jarrad, F. W. Great Britain Hydrographic Dept
1894.China Sea Directory vol. 4 (Third Edition). London
by Goalen, W. N. Great Britain Hydrographic Dept
1904.Sailing Directions for Japan, Korea, and adjacent Seas. London1904
    by Langdon, C. H.


(Joseon) East Sea on Korean Maps

There are so many antique map in Korea but there are only small number of Map which describes East Sea東海. But those maps they descrbes "East Sea" just on THE SHORE of EAST COAST of The Peninsula, where today's Donghae-City. It is not deep water on the Sea of Japan. They use the word just for a sea in the "east" direction, not East sea paticular name and clear definiation. It is same logic that Japan called it North Sea till Edo-Era. So the Sea of Japan should be re-named "North Sea"? Some Korean record said it is "Big Sea大海 over the East Sea東海. Maybe the Big Sea means Sea of Japan in their recognization.

1530 Paldo-Jido

After D'anville introduced Corea throuhgh Chinese Map around 1720's, "Mer Du Coree" is increased temporary, till La Perouse's discovery navigation around Mer Du Japon and Detroit de Coree. They think much importance on actual survey and explorer ,like La Perouse, Broughton, and Krusenstern than just a writing like D'anville. Before actual survey around Sea of Japan, some French maps describes East Sea as "Sea of Japan"part and some as French map "Broughton Bay "part. So it is not concreted recognizaton of Mer du Coree or east sea.
Today, we call this area as "East Korean Gulf/TongChosongMan東朝鮮湾 Two map below describes East Sea, just a coastal area between 豆満江-Wonsan元山-Ulluengdo鬱陵島. It is not on the deep water on the Sea of Japan. On Franch maps Mer du Coree or Gulf de Coree seems to be referenced from those Korean antique maps? And the Mer du Coree is change to Korean Gulf or East Korean gulf,Broughton Bay. .See the two european map after the two map below.
Left:18世紀末期 『輿地図』 朝鮮日本琉球国圖 古4709-78 Korea
Right:1847-1852(1876)海國圖志(淸,魏源,1794-1856) China

Also see the previous post about Mer du Coree and Broughton bay.

Following Korean's logic, Pacific Ocean should all renamed "East Sea" because Japan call Pacific ocean coastal area as 東海To-kai(East Sea) and South China Sea shuold renamed "East Sea" because vietnam call it Vien Dong(East Sea) so all the area on the Internatinal charts become East Sea around all East Asia. It must makes sailor confusion. Dont you think it is smart idea to rename it?

Image referenced from this site