Japan recounted the number of islands it had and realised it had missed out nearly 7,000 of them when it first counted them in 1987.
After 35 years, the number of listed Japanese islands is expected to more than double from 6,852 to 14,125, according to a source familiar with the matter.
The increased number is thanks to improved accuracy in geospatial mapping with the government expected to release the new figure as early as March.
Although this number could change as the Geospatial Information Authority of Japan, or GSI, is making final adjustments, the source said.
The digitalization of maps is unlikely to change the size of Japanese territory or territorial waters, the source told Kyodo News on Monday.
The new figure could affect entries in educational and other materials. Up until now, the government of Japan was using the figure released in 1987 by the Japan Coast Guard.
At the time, the coast guard listed islands with a circumference of 100 metres or greater by hand on a map of Japan. Islands in lakes or river sandbanks were not included in the total.
In the latest survey, the government counted islands using a computer based on GSI’s electronic land map in 2022 and cross-referenced the map with past aerial photographs and other data, while excluding artificially reclaimed land.
While the computer detected over 100,000 islands, only those with circumferences of 100 metres or greater were selected for the official list.
Islands in the survey are defined in line with the United Nations Convention on the Law of the Sea, which states that an island is a ‘naturally formed area of land, surrounded by water, which is above water at high tide’.
The total size of national territory is calculated using the same digital map irrespective of listed islands, while the extent of territorial waters will not be affected as remote Japanese islands are subject to a separate survey.
Nagasaki and Kagoshima prefectures in southwestern Japan had 1,479 and 1,256 islands, respectively, while 1,473 were listed in Hokkaido, northern Japan.
Moves to reassess the number of listed islands came amid criticism that data was old and the true figure could be vastly different.
In December 2021, a ruling Liberal Democratic Party lawmaker told a parliamentary session ‘an accurate understanding of the number of islands is an important administrative matter that is related to the national interest’.
MORE : Mystery orb that washed up on Japanese beach may finally have been identified
MORE : Mystery orb washes up on Japanese beach and no one can work out what it is