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909 B
Markdown
18 lines
909 B
Markdown
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# Map data
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`japan_prefectures.geojson` derives from **Natural Earth**
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(<https://www.naturalearthdata.com/>), *Admin 1 – States, Provinces*, 1:10m
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cultural vectors, release v5.1.2. Natural Earth's map data is in the public
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domain:
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> All versions of Natural Earth raster and vector map data found on this
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> website are in the public domain. You may use the maps in any manner,
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> including modifying the content and design, electronic dissemination, and
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> offset printing.
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`tool/maps/japan_prefectures.py` builds the file: it keeps Japan's 47
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prefectures, simplifies their outlines (Douglas–Peucker, 0.006°), drops islands
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too small to see (each prefecture keeps its largest), and rounds coordinates to
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4 decimals. The outlines are an approximation for display, not survey-accurate
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data. Regions are named by their ISO 3166-2 codes (`JP-01` … `JP-47`), with
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Natural Earth's English and Japanese names.
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