A5 is a geospatial index that partitions the world into pentagonal cells. The cells are available at 31 resolution levels, from a handful covering the whole world down to less than 30mm², and every cell at a given resolution has exactly the same area. Each cell is identified by a 64-bit integer, which is frozen from v1.0: an A5 cell ID stored today will refer to the same place in the future.

Once data is in cells, very different datasets can be joined, aggregated and compared directly: points can be counted per cell, as with the density of holiday rentals across a city, and regions such as countries or parcels of land become coverings, sets of cells which support union, intersection and difference.

Key strengths

• Equal area, single topology: every cell is an exactly equal-area pentagon with 5 neighbors, so aggregates are free of bias from unequal cell sizes. See A5 vs H3.
• Built for big data: cell IDs follow a space-filling curve that never crosses itself, so polygons and coverings are compact ID ranges. Billions of cells can be filled, combined and counted in seconds.
• Fast & rich API: high-level functions for indexing, hierarchy, traversal and coverings, with a native Rust core.
• Strong ecosystem: official libraries for TypeScript, Python and Rust, with DuckDB, PostgreSQL, R, QGIS and deck.gl integrations. See the Ecosystem.

Where to start

• Quickstart: index your first cell in your language of choice
• DuckDB playground: use DuckDB to experiment with A5
• Examples: interactive examples showcasing the system
• API Reference: every function, with snippets in each language
• What's new: the changes in v1.0

A5 is open source and licensed under the Apache 2.0 License.

Links

• Website: a5geo.org
• Bugs or feature requests: GitHub Issues
• Questions and discussion: join the community on Slack