Gaihozu meaning "maps of the outer lands" are overseas maps compiled for military purposes by the former Imperial Japanese Army. From the early Meiji era until the end of World War II (WWII), mapping of Japan was conducted primarily by the Land Survey Department of the General Staff of the Japanese Imperial Army. The department also produced maps of areas outside the Japanese territory at scales of 1:25,000 to 1:500,000, and its geographical coverage extended north to Alaska, east to the United States (US) mainland the Isthmus of Panama, south to Australia, and west to Pakistan, parts of Afghanistan eastern parts of African continent. The maps were produced in various ways, including through surveys by Japanese survey teams, reproductions of maps produced abroad and secret surveys. Despite these maps being compiled for military purposes, they are of extremely high value, offering detailed records of the geoscientific landscape of the Asia-Pacific region in the late 19th and early 20th centuries.

Most of Gaihozu maps were classified and managed as top-secret, and many of them were destroyed or confiscated at the end of WWII. However, thanks to the efforts of Japanese researchers at the time, a large number of maps were transferred to institutions such as Tohoku University. The Gaihozu Digital Archives manage the electronic catalog (metadata) and digital images of the Gaihozu maps that remain mainly at Tohoku University, as well as Ochanomizu , Kyoto and Osaka Universities, providing a public access system for browsing map images to facilitate their peace-seeking academic use.

■Gaihozu Digital Archives website：https://gaihozu-tohokugeo.hub.arcgis.com/