Bathymetry

The base theme's bathymetry feature type provides topographic representations of underwater areas, such as parts of lake beds or ocean floors. The geometries are derived from vectorized bathymetric data products built from ETOPO1 and GLOBathy data.

Bathymetry features carry Polygon or MultiPolygon geometries and a single classifying property, depth, which gives the depth level of the feature in meters below the water surface. See the bathymetry schema reference for the full column definitions.

Stacked depth levels

Bathymetry is delivered as a set of stacked depth levels. Each depth level is a coverage polygon set: the features with depth = d together cover every point of the earth's surface where the water is deeper than d meters.

Practically, this means entities with a lower depth will always totally cover entities with a higher depth:

• depth = 0 covers all water — oceans and the lakes captured by GLOBathy.
• depth = 200 covers only the water that is deeper than 200 m.
• depth = 4000 covers only the water that is deeper than 4000 m.

A point on the ocean floor at 3,500 m depth is therefore covered by every level from 0 up to the deepest level shallower than 3,500 m. Land is not covered by any level.

To render a classic bathymetric tint map, draw the levels stacked from shallow to deep: paint depth = 0 first in the lightest color, then paint each successively deeper level on top in a darker color. The cartography.sort_key property encodes this recommended stacking — features with a lower sort_key should be drawn in front of features with a higher sort_key. To extract a single disjoint depth band instead (for example, water between 200 m and 1000 m deep), subtract the deeper level's coverage from the shallower level's coverage.

Takeaways

• Land is not covered. Bathymetry polygons only exist over water; no masking against land or water layers is needed.
• Geometries are grid chips. Instead of a small number of world-spanning multipolygons, each depth level is delivered as many polygons chipped to a roughly 1° grid, the same way Overture's ocean water polygons are delivered. Spatial filters (for example, bbox predicates) are much more effective as a result.
• Semantics are "deeper than." A feature with depth = d means "the water here is deeper than d meters," and levels overlap by design. Count on multiple features covering the same point — one per depth level shallower than the water at that point.

Data access

Bathymetry data is available at:

provider	location
Amazon S3	s3://overturemaps-us-west-2/release/<release>/theme=base/type=bathymetry/*
Azure Blob Storage	https://overturemapswestus2.blob.core.windows.net/release/<release>/theme=base/type=bathymetry/*

See the base guide overview for general information about the base theme, including licensing and release cadence.