Japan prefecture geometry for GRAPH("JAPANMAP")
Source: Natural Earth, Admin 1 - States, Provinces, 1:10m, version 5.1.1.
https://www.naturalearthdata.com/downloads/10m-cultural-vectors/10m-admin-1-states-provinces/
https://www.naturalearthdata.com/about/terms-of-use/
Download: https://naciscdn.org/naturalearth/10m/cultural/ne_10m_admin_1_states_provinces.zip
Archive SHA256: efc59726337323058f9446210adc96673179cd344e053666ee3d28cb58ba2b05
License: Public domain. Attribution is not required by Natural Earth.
Retrieved: 2026-09-08.
Extraction: adm0_a3=JPN; verified unique JP-01..JP-47 and Japanese names.
All rings retained; coordinates rounded to 6 decimal degrees; no simplification.
47 regions, 12669 vertices. Coordinates are longitude/latitude (WGS84).
Boundaries follow the Natural Earth dataset's de facto representation.
Small islands and exact boundaries are limited by the source's map scale.
No downloads or third-party GIS libraries are needed to compile or run BASIC.
The extracted JSON is embedded into generated C by the transpiler.
