Japan has started surveying border-area islands, whose owners and usage often remain a mystery, to maintain its territorial waters and far-flung locations in its exclusive economic zone (EEZ).

Many of these outlying islands serve as fiducial points to mark the boundaries of territorial waters and the EEZ.

Government officials also hope that updated, detailed information on ownership and usage will help protect against intrusions, occupations and other illegal activities by neighboring countries.

Japan has the world’s sixth largest EEZ, including its territorial waters, with 525 islands and islets around its borders, 465 of which are uninhabited.

However, the owners of many land plots on 99 isles--60 inhabited and 39 uninhabited--have not been identified, and the use of the private land is unclear.

“The ocean policy is vitally important for Japan, which is surrounded on all sides by the sea,” Prime Minister Shinzo Abe said at a meeting of the Headquarters for Ocean Policy in May. “The success of the policy will directly lead to benefits for our nation.”

The third Basic Plan on Ocean Policy, approved by the Cabinet that month, specifies “comprehensive maritime security” to underline the government’s determination to protect and manage islands near Japan’s borders.

Based on the plan, the Cabinet Office started surveying the circumstances surrounding private land on the islands.

Most deserted islands are currently owned by the central or local governments.

The Japanese government claimed ownership of a number of uninhabited islets after Chinese government vessels started trespassing in territorial waters around the Senkaku Islands, which are controlled by Tokyo but also claimed by Beijing.

In general, lot numbers must be identified to examine property registration records for private land. But identifying such numbers for numerous land plots on border-area islands is difficult partly because ownership rarely changes.

“We repeatedly go to and return from some of such islets for two months (to identify lot numbers),” a Cabinet Office official said.

Although land record certificates for all uninhabited islets have been found, Tokyo is still struggling to identify certificates for islands that are inhabited.

The government has decided to introduce an integrated system for information about border-area islands. That way, the data can be easily shared among ministries and agencies, such as the Defense Ministry, the Japan Coast Guard and the Japan Meteorological Agency, as well as local governments and private organizations.

The system will be used to check if coastal lines have changed or if land plots are being used illegally by non-Japanese so that countermeasures can be quickly devised if necessary.