Announcement of 2014 Planimetric reports on the land area by prefectures and municipalities in Japan
- The nation’s area measured by the Digital Japan Basic Map proved to be 377,972.28km² -
The Geospatial Information Authority of Japan (GSI) compiled and announced Planimetric reports on the land area by prefectures and municipalities in Japan as of October 1st, 2014.
With regards to Planimetric reports on the land area by prefectures and municipalities in Japan up to 2013, the released areas were compiled based mainly on the Topographic map of 1:25,000, however, the accuracy of the area was improved by switching the map used as the measurement base to the Digital Japan Basic Map.
As a result, the nation's area as of October 1st, 2014 is 377,972.28km2
Change of measurement method
Using as the basis the area measured by the digitizer from the Topographic map of 1:25,000 in 1988, up until 2013, we conducted calculations by adding the landfill areas etc. notified in each year. However, many issues were inherent in this method like the inaccuracy due to measurement errors compared to the current technology, and its insufficiency to reflect natural changes in the coastline etc.
Because of this, we decided to conduct area measurements using the latest digital maps (Digital Japan Basic Map) from 2014 onward. Specifically, by applying the coordinate values of the Digital Japan Basic Map directly to the calculations, it has become possible to calculate area with higher precision than by using the digitizer measurements based on the Topographic map of 1:25,000.
As well, by using the latest coastline data that reflect natural changes like erosion and sedimentation, we have been able to conduct area measurements that are more consistent with the present conditions.
By changing the measurement method and switching the map providing the basis for the measurements, the national land area as of 2014 changed from 377,961.73km2 in 2013 to 377,972.28k m2 and the area of many municipalities and prefectures changed as well.
The gathered results for Planimetric reports on the land area by prefectures and municipalities in Japan were released in the Geospatial Information Authority of Japan’s webpage below.
The announcement of national land area was first implemented by the Grand Council of State (Dajokan)'s Division of Statistics (Tokeiin) in 1882, and shares a history as long as that of population statistics. Since 1960, the Geospatial Information Authority of Japan has been releasing the information annually as Planimetric reports on the land area by prefectures and municipalities in Japan. The area values, which become basic data for population density calculations in the national census report and local allocation tax calculations (Local Allocation Tax Act, Article 12), are used in a variety of fields.