# Third-party notices

## Historical Basemaps

André Ourednik and contributors: https://github.com/aourednik/historical-basemaps . Source pinned to commit da7a4b735ecef70aebdc9c73e409d8a2500d50f3, files world_600.geojson, world_800.geojson, world_1492.geojson. GPL-3.0; full license in LICENSE. Selected Sui, Tang and Ming continental main entities were simplified at 0.018° and rounded to four decimals. Original names/precision attributes and warnings are retained. Other snapshots with unresolved errors are withheld; no 1900 boundary is used in this edition. See HISTORY_MAP_NOTES.txt for audit and exact display limits. This prototype and derived history-map data are distributed under GPL-3.0-or-later.

## Natural Earth

Physical land and lake geometries: Natural Earth 1:50m physical land and lakes, feature subset intersecting East Asia. These are natural geometry, not national boundaries. Rivers: 1:50m rivers plus 1:10m local Hai/Yongding river lines. Modern physical geography does not reconstruct historical river courses, shorelines or jurisdiction.

Selected physical region labels and summits: ne_10m_geography_regions_polys and ne_10m_geography_regions_elevation_points. Labels use selected anchors; they do not draw landform boundaries. Editorial alternate anchors avoid map overlays. Everest 8848.86m and selected Taibai/Beijing peaks use official sources linked in assets/terrain.js; other approximate heights are marked. Terrain raster is separately sourced.

Public domain: https://www.naturalearthdata.com/about/terms-of-use/
Data: https://github.com/nvkelso/natural-earth-vector
Physical labels: https://www.naturalearthdata.com/downloads/10m-physical-vectors/10m-physical-labels/

## D3 v7.9.0

Copyright 2010–2023 Mike Bostock. ISC license.

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

## Museum illustrations

The Cleveland Museum of Art Open Access collection. The 11 selected images are marked CC0 in collection metadata. Object captions retain dates, object identities and gallery links. These are material-culture references, never asserted to depict a selected event. Rights information: https://www.clevelandart.org/open-access . Metadata is retained in content/illustrations.json.

- 良渚文化玉璧 — https://clevelandart.org/art/1917.974 — 克利夫兰艺术博物馆 · CC0
- 新石器时代甘肃陶瓶 — https://clevelandart.org/art/1930.333 — 克利夫兰艺术博物馆 · CC0
- 商代青铜鼎 — https://clevelandart.org/art/1960.288 — 克利夫兰艺术博物馆 · CC0
- 东周青铜钟 — https://clevelandart.org/art/1962.44 — 克利夫兰艺术博物馆 · CC0
- 西汉熊形席镇 — https://clevelandart.org/art/1994.203 — 克利夫兰艺术博物馆 · CC0
- 北魏礼佛僧人像 — https://clevelandart.org/art/1962.213 — 克利夫兰艺术博物馆 · CC0
- 唐代鸾鸟花卉纹镜 — https://clevelandart.org/art/1973.74 — 克利夫兰艺术博物馆 · CC0
- 南宋《货郎图》 — https://clevelandart.org/art/1963.582 — 克利夫兰艺术博物馆 · CC0
- 元代《九歌图》 — https://clevelandart.org/art/1959.138 — 克利夫兰艺术博物馆 · CC0
- 明代成化斗彩婴戏杯 — https://clevelandart.org/art/1957.61 — 克利夫兰艺术博物馆 · CC0
- 清初《四季山水册》一页 — https://clevelandart.org/art/1955.302.8 — 克利夫兰艺术博物馆 · CC0

## Mapzen / Tilezen terrain surface

Modern hypsometric color and hillshade rasters derived from Terrarium elevation tiles hosted in the AWS Open Data Terrain Tiles registry. Full upstream provider attributions and processing/resolution notes: [TERRAIN_ATTRIBUTION.md](TERRAIN_ATTRIBUTION.md) in the deployed assets. Source registry: https://registry.opendata.aws/terrain-tiles/. Global GMTED2010 and SRTM terrain data courtesy of the U.S. Geological Survey; global ETOPO1 data courtesy of NOAA. Accessed 2026-10-22. See `scripts/build-relief.py` for reproducible processing.