# Map sources

## Worldwide regional and close detail

The three approved local images below remain unchanged. New geographic tiles use
the same NASA GIBS Blue Marble Shaded Relief source and land/sea colour treatment.
The MODIS/SRTM Water Mask supplies independent water classification so mountain
shadows do not become false lakes. No NASA endorsement is implied.

Tiles use CRS84 / EPSG:4326. The 500m tile matrix has 512-pixel tiles: z5 covers 9°
and z7 covers 2.25°. Near the poles, wider geographic cells use the same WMS source
to retain physical sampling without excessive narrow tiles. Baked source relief
is approximately 500m imagery, not live elevation or street-level data.

- [GIBS geographic services](https://nasa-gibs.github.io/gibs-api-docs/access-basics/)
- [Published layer and tile-matrix definitions](https://gibs.earthdata.nasa.gov/wmts/epsg4326/best/1.0.0/WMTSCapabilities.xml)
- [MODIS/SRTM Water Mask colour mapping](https://gibs.earthdata.nasa.gov/colormaps/v1.3/MODIS_Water_Mask.xml)

Anonymous tile delivery is from `gibs.earthdata.nasa.gov`, with a bounded local
cache. No paid service, account, location permission or whole-world detailed
download is required. The camera's viewed area determines requests. Temporary
source failures retain the last valid terrain. See the project checkpoint notes
for resource limits and graphics-testing limitations.

## Current terrain globe proof

The current user direction preserves the regional/Scotland terrain and brings
Earth into the same realistic/semi-realistic family. The previous cartoon far-view
direction is superseded. Reference screenshots are not used as textures.

Earth now uses a separate 4096 × 2048 NASA GIBS Blue Marble Shaded Relief raster,
with the same natural land colour and blue-water treatment as the closer tiers.
No low-resolution upscaling, blurred land or posterised palette is used. Its GPU
texture dimensions are unchanged. The permanent circular Arctic ice cap remains
an art convention, not a claim about current sea ice. Greenland and Antarctic
ice derive from the geographic source.

All three layers use separate NASA GIBS Blue Marble Shaded Relief
crops, downloaded 10 September 2026. This is a historical MODIS composite with
baked relief, not live imagery, street-level imagery or real-time 3D elevation.
Scotland's lochs, islands and terrain texture derive from the imagery, not invented
landforms. Colours are brightened, water is recoloured and local contrast is
adjusted to match the supplied direction. No NASA endorsement is implied.

- [NASA Blue Marble collection](https://science.nasa.gov/earth/earth-observatory/collections/blue-marble/)
- [NASA GIBS access documentation](https://nasa-gibs.github.io/gibs-api-docs/access-basics/)
- [NASA imagery use guidance](https://www.nasa.gov/nasa-brand-center/images-and-media/)
- [Natural Earth public-domain terms](https://www.naturalearthdata.com/about/terms-of-use/)

Source WMS: `https://gibs.earthdata.nasa.gov/wms/epsg4326/best/wms.cgi`

Common request parameters: `SERVICE=WMS`, `VERSION=1.1.1`, `REQUEST=GetMap`,
`LAYERS=BlueMarble_ShadedRelief`, `STYLES=`, `SRS=EPSG:4326`, `FORMAT=image/jpeg`.

| Layer | Longitude/latitude bounds W,S,E,N | Image size |
| --- | --- | --- |
| Earth | -180,-90,180,90 | 4096 × 2048 |
| Region | -32,33,35,73 | 3072 × 2048 |
| Scotland | -10,53,3,62 | 2048 × 2048 |

The close layer is a separate higher-detail geographic crop, not an enlargement
of the regional or Earth asset. Native Blue Marble detail is approximately 500 m;
the output image dimensions do not imply finer geographic source resolution.
No external tile service is needed at runtime.

Scotland picking uses the existing Natural Earth GB-SCT MultiPolygon, independently
of visual raster data. It retains islands and holes but is a global-scale map
boundary, not a cadastral survey. Fine imagery shorelines may differ slightly from
that generalised boundary. No neighbouring territory is silently classified as
Scotland. Raster crops share WGS84 registration throughout transitions.

Original source bytes are preserved in `data/terrain-source`; output and source
SHA-256 hashes are in `public/terrain/manifest.json`. Preparation is reproducible
with `scripts/prepare-hybrid-terrain.py`. Use `--earth-only` to leave the accepted
regional, Scotland and selection files untouched. EOX imagery was inspected as a possible
source but is not included or used. No external DEM tiles are included.

See [historical project sources](/SOURCES.md) for earlier retained, inactive assets.