A5 grid

A5 is a global pentagonal Discrete Global Grid System: the Earth is wrapped onto a dodecahedron whose 12 faces are tiled with equilateral pentagons, then subdivided (aperture-4 above resolution 1) on a true equal-area projection. Pentagons let every cell nest exactly into its parent while keeping a constant ground area at each resolution — see https://a5geo.org/. M3S wraps the official pya5 library.

The interactive explorer below is rendered with deck.gl and behaves like the h3geo.org map: the A5 resolution follows the zoom and pentagons are generated in the browser for whatever is in view. Two neighbouring resolutions are shown at once — the current level with a darker, heavier border and the next finer level with a lighter, thinner one — so the aperture-4 nesting stays visible. It is powered by a5-js — the same A5 implementation pya5 is the Python port of, pinned to the version M3S ships — so the hexadecimal cell ids and pentagon edges match M3S exactly. GIS-native (lon, lat) order is used throughout.

Why A5?

A5 delivers the two properties most grids only approximate, at the same time: every cell at a resolution covers exactly the same ground area, and every cell nests exactly into its parent — from continent-sized cells down to under 30 mm². If you are building statistics where both fair comparison and strict hierarchy matter, this is the strongest choice in M3S. The tradeoffs are youth and shape: the ecosystem is far smaller than H3’s, and pentagon adjacency is less regular than hexagons. Reach for H3 grid when tooling support matters more than exactness, or EA-Quad grid when you want equal-area squares labelled in kilometres.

Usage

Encode a point and tile a small bounding box around Paris — same result in Python and JavaScript (both call the shared core):

Python

import m3s

cell = m3s.A5.from_geometry((2.35, 48.86))            # (lon, lat)
cells = m3s.A5.from_geometry((2.2, 48.8, 2.4, 48.9))  # bbox
print(cell.id, len(cells))

JavaScript

import * as m3s from "m3s";
await m3s.ready();

const cell = m3s.A5.fromPoint(2.35, 48.86);            // (lon, lat)
const cells = m3s.A5.fromBbox([2.2, 48.8, 2.4, 48.9]); // bbox
console.log(cell.id, cells.length, m3s.A5.cellAreaM2(8)); // equal-area

from _deckmap import DeckExplorer, read_grid_js


DeckExplorer(
    center=(9.5, 48.5),
    zoom=5,
    grid_js=read_grid_js("a5"),
    hover="#999933",
    wasm=True,
)