GEBCO Bathymetry Tiles

Convert GEBCO gridded bathymetry data into tiles for use with MapLibre GL:

• Terrain-RGB raster tiles — for depth shading (color-relief), hillshade, and 3D terrain
• Vector contour tiles — pre-generated bathymetric contour lines with non-uniform intervals

Part of the OpenWaters project — building modern open-source tools for marine navigation.

Contributing

Local (with dependencies installed)

# Install dependencies (macOS)
brew install gdal tippecanoe jq rio

# Or on Ubuntu/Debian
sudo apt install gdal-bin python3-gdal python3-numpy jq bc
# tippecanoe: build from https://github.com/felt/tippecanoe
# rio-rgbify: pip install rio-rgbify

# Run the full pipeline (downloads ~7.5 GB)
./scripts/pipeline.sh

# Or for a regional extract (much faster for testing)
BBOX="-85,20,-70,35" ./scripts/pipeline.sh

Docker

docker build -t gebco-tiles .

# Full global build
docker run --rm -v $(pwd)/data:/app/data -v $(pwd)/output:/app/output gebco-tiles

# Regional extract (Bahamas)
docker run --rm -e BBOX="-85,20,-70,35" \
  -v $(pwd)/data:/app/data -v $(pwd)/output:/app/output gebco-tiles

GitHub Actions

The workflow at .github/workflows/ci.yml can be triggered manually:

1. Go to Actions → Build → Run workflow
2. Optionally set a bounding box for a regional build
3. Tiles are deployed to GitHub Pages when complete

Preview

Start the Vite dev server to preview the map locally:

npm install
npm run dev

This serves the web viewer at http://localhost:5173 with the built tiles from output/ as the public directory.

You can also drag any .pmtiles file into the PMTiles Viewer to inspect tile contents.

Pipeline scripts

Script	Purpose
scripts/pipeline.sh	Runs the full pipeline end to end
scripts/download.sh	Downloads GEBCO GeoTIFF (with optional BBOX clip)
scripts/build-terrain-rgb.sh	Builds Terrain-RGB raster tiles (MBTiles + PMTiles)
scripts/contour	Generates contour vector tiles (PMTiles)
scripts/smooth-contours.py	Chaikin corner-cutting smoothing for contour lines
scripts/config.sh	Shared configuration (intervals, paths, helpers)

Configuration

Set environment variables before running:

Variable	Default	Description
BBOX	(empty = global)	Bounding box "west,south,east,north" (commas)
MAX_ZOOM	14	Maximum contour tile zoom level
TERRAIN_MAX_ZOOM	9	Maximum terrain-RGB tile zoom level
THREADS	nproc	Parallel processing threads
FORCE	(empty)	Set to 1 to rebuild all cached files
GEBCO_URL	GEBCO 2025	Override the download URL

Data sources

This pipeline uses GEBCO (15 arc-second global grid). For higher resolution in specific regions, you can substitute or merge with:

• NOAA BlueTopo (2-16m, US waters) — s3://noaa-bathymetry-pds/BlueTopo/
• EMODnet (~3.6-115m, European waters)
• NOAA CUDEM (~3-10m, US coast)

Use gdalwarp or gdalbuildvrt to merge higher-res regional data with GEBCO before running the contour generation step.

See RESEARCH.md for the full research summary.

License

Scripts: MIT. Output data inherits GEBCO's terms (public domain, attribution required).

Attribution: GEBCO Compilation Group (2025) GEBCO 2025 Grid (doi:10.5285/37c52e96-24ea-67ce-e063-7086abc05f29)

Prior Art

• https://github.com/versatiles-org/opendem-gebco-bathymetry/
• https://github.com/shiwaku/gebco-2025-grid-tile-on-maplibre