# Map data provenance

Made with [Natural Earth](https://www.naturalearthdata.com/).

Natural Earth's raster and vector map data are in the **public domain**, including commercial use and modification. No attribution is required; this project retains it for transparency. See the [Natural Earth terms of use](https://www.naturalearthdata.com/about/terms-of-use/).

Downloaded 2026-10-13 from the Natural Earth vector repository, commit `ca96624a56bd078437bca8184e78163e5039ad19`:

- [50m country polygons](https://raw.githubusercontent.com/nvkelso/natural-earth-vector/ca96624a56bd078437bca8184e78163e5039ad19/geojson/ne_50m_admin_0_countries.geojson)
- [50m populated places](https://raw.githubusercontent.com/nvkelso/natural-earth-vector/ca96624a56bd078437bca8184e78163e5039ad19/geojson/ne_50m_populated_places.geojson)

## Local transformations

All 242 polygon features and all 1,251 populated-place features were retained. Coordinates were rounded to four decimal places (approximately 11 metres of latitude). Geometries were not simplified or replaced. Unused metadata was removed, English display names were mapped to `name`, and JSON was minified. `country-labels.geojson` uses Natural Earth's supplied label coordinates rather than polygon centroids. Feature IDs retain `NE_ID`.

| File | Features | Bytes | Gzip bytes, indicative |
| --- | ---: | ---: | ---: |
| countries.geojson | 242 | 1,880,528 | 685,070 |
| country-labels.geojson | 242 | 36,807 | 5,754 |
| cities.geojson | 1,251 | 207,201 | 25,877 |

Properties: countries have `name`, `code`; country labels have `name`, `rank`, `minZoom`; cities have `name`, `rank`, `minZoom`, `capital`. All coordinates are GeoJSON longitude, latitude in WGS84. Use `name` for MapLibre labels; smaller rank means higher prominence. `minZoom` records the source's recommended label visibility.

These are contemporary cartographic reference boundaries and place names, not reconstructed historical borders. Natural Earth's 1:50 million scale is appropriate for world and regional orientation; it does not provide street, building, or survey precision. Political boundaries reflect the source dataset's conventions and do not express endorsement of territorial claims. The game may support more precise pins than the basemap detail.

## Integrity

Original country source SHA-256: `3e458fc036ad0a66411f2c1e6cac49c5d7bfb81cb1123bc513b22511a2b7fdeb`.

Original city source SHA-256: `da4662b7bbfeb897d02f228c5839131dce27acff5717630f91ccff4f67828ee7`.

The application serves these files locally. No external tile service, mapping API key, or per-map-view fee is required.

## Map label font

The `fonts/Noto Sans Regular/` directory contains unmodified Noto Sans Regular glyph PBF files from the [official MapLibre demotiles repository](https://github.com/maplibre/demotiles/tree/601ae60796ceceda2cbd2ed3d2ea92d17a84be4b/font/Noto%20Sans%20Regular), commit `601ae60796ceceda2cbd2ed3d2ea92d17a84be4b`, retrieved 2026-10-13. These fonts are licensed separately under the SIL Open Font License 1.1; the upstream license is preserved in `fonts/Noto Sans Regular/LICENSE.md`.

Bundled ranges: `0-255`, `256-511`, `512-767`, and `8192-8447`. They cover all name strings in the bundled country/city data, including their uppercase variants. The four glyph files total 333,597 bytes. Each file was verified against the upstream Git blob hash. Localize names or add new labels only after adding any required glyph ranges.

MapLibre style configuration:

```js
glyphs: '/maps/fonts/{fontstack}/{range}.pbf'
// On every symbol label layer:
'text-font': ['Noto Sans Regular']
```

## State and province borders

Added 2026-10-16 from Natural Earth v5.1.0 (public domain): `state-province-borders.geojson` and `country-land-borders.geojson`. These use the official 1:10m administrative line datasets, reduced with approximately 250m local metric simplification. Shared junction endpoints are preserved, and antimeridian crossings are split. The adjacent `*-source.json` records preserve source URLs, input/output SHA-256 hashes, versions, and validation details. Each output is one MultiLineString feature with empty properties: no state, province, or city names are supplied to label layers. Country labels remain a separate layer.

## Reviewed city areas — October 16, 2026

The scoring overlay has separate sources from the basemap. [Download the modified geographic database](./city-boundary-derivatives.geojson). It contains named geographic areas and source metadata, without question IDs, clues or answer mappings.

- OpenStreetMap administrative/locality boundaries: © [OpenStreetMap contributors](https://www.openstreetmap.org/copyright), used and modified under [Open Database License 1.0](https://opendatacommons.org/licenses/odbl/1-0/). The OSM-derived features in the linked geographic database are made available under ODbL 1.0. Changes include clipping, unions, local metric edge margins, topology-preserving simplification and coordinate rounding; per-feature metadata describes the sources and processing. The Araneta Coliseum point is derived from OSM building way 4935803.
- French commune boundaries: [Contours administratifs](https://www.data.gouv.fr/datasets/contours-administratifs), ODbL 1.0; covered by the same derivative-database download and license.
- U.S. Census Bureau [TIGERweb places](https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/Places_CouSub_ConCity_SubMCD/MapServer): public domain. Small local margins have been applied to municipal outlines. San Francisco instead uses [DataSF shoreline-clipped Census 2020 block groups](https://data.sf.gov/Geographic-Locations-and-Boundaries/Census-2020-Blocks-Groups-for-San-Francisco-Clipped-t/6rf8-dnst), [PDDL 1.0](https://opendatacommons.org/licenses/pddl/1-0/), with remote islands removed and a local margin.
- Anaheim: [City of Anaheim GIS](https://gis.anaheim.net/map/rest/services/CityBoundary/MapServer/0), city boundary plus an approximately 1 km edge margin.
- Soweto: Statistics South Africa is the source of the basic Census 2011 data. Main place 798026 was supplied through Adrian Frith’s census API; the game area results from our own processing. [Statistics South Africa terms](https://www.statssa.gov.za/?page_id=425), [data mirror](https://census2011.adrianfrith.com/place/798026/map). This feature retains its separate attribution permission and is not relicensed as ODbL.
- Individually reviewed Natural Earth urban footprints remain public domain; some have been restricted to a documented local extent.

Accepted regions are forgiving game interpretations, not surveyed legal boundaries. The original geographic sources do not endorse this game. Historical saved guesses may show an earlier Natural Earth outline.