The East Sea is historically and geographically located northeast of the Asian Continent and west of the Pacific Ocean and is surrounded by the Maritime Province and Sakhalin Island in Russia and the Japanese Islands. The East Sea was also called "Sea of Korea" and "Sea of Chosun," and it has the Tatar Strait to its north and the Korea Strait to its south.

It is said that the East Sea was created about 30 million years ago in the early quaternary period of the Cenozoic Era. There are two theories on the cause of its formation; the ingression sea theory where what was once a continent became a sea and the continental drift theory where the Japanese Islands, originally attached to the continent, moved east and formed a sea.

The East Sea forms an ellipse with the northeast-southwest apse line. It is 1,700 kilometers long from north to south, maximum 1,100 kilometers wide from east to west, and 1,361 meters deep in average. Particularly, the area near the Maritime Province of Russia and the Korean Peninsula is deeper and forms a steep slope of about 3,000 meters. The deepest part is on the northeast near the Ogiri Island and 3,762 meters deep, and its capacity is 1.361 million cubic kilometers.
Particularly, the continental shelf with the depth of water less than 200 meters is formed narrowly along the coast and covers an area of 280,000 square kilometers. The deep ocean floor with the depth of water exceeding 3,000 meters is 300,000 square kilometers in area.

In 1920s, the first modern Korean oceanographic survey was initiated for the purpose of helping fishery activities. After the World War Ⅱ, a serial oceanographic survey conducted by the National Fisheries Research and Development Institute (NFRDI) and tide observations from coastal stations by the National Oceanographic Research Institute have made the compilation of a large quantity of oceanic date and commenced modern oceanographic understanding of the sea around Korea. The improvement of observational techniques enables us to produce more accurate and voluminous data which often becomes a problem of managing the acquired data. The cooperative researches between the neighboring states are also in progress for mutual benefit which ensures a broader prospective in the regional oceanography.

This Atlas was prepared by integrating various oceanographic parameters from the southwestern region of the East Sea based on interdisciplinary observational programs carried out during last four years between 1994-1997 conducted by KORDI. In addition, historical data of 35 years collected by NFRDI were also incorporated in the data analyses.