Maidenhead grid

The Maidenhead Locator System used by amateur radio operators. Fields and squares tile the globe in 2° × 1° squares (precision 2), refinable into subsquares.

The interactive explorer below is rendered with deck.gl and behaves like the h3geo.org map: the Maidenhead precision follows the zoom and locators are generated in the browser for whatever is in view. Two neighbouring precisions are shown at once — the current level with a darker, heavier border and the next finer level with a lighter, thinner one — so the field → square → subsquare nesting stays visible. The field/square/subsquare encoder is the exact one in m3s.maidenhead, reproduced in JavaScript so the locators and edges match M3S. GIS-native (lon, lat) order is used throughout.

Why Maidenhead?

Maidenhead is the amateur-radio convention: “JN58td” is short enough to say in a voice contact, every logging program and contest sponsor understands it, and distances between locators are standardised for award scoring. If you are logging QSOs or plotting station coverage, it is the only grid the rest of the hobby speaks. Beyond radio there is little reason to pick it: cells are latitude-stretched rectangles with an alternating 10/24 subdivision. For general-purpose short location codes use Plus Codes grid; for database indexing, Geohash grid.

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.Maidenhead.from_geometry((2.35, 48.86))            # (lon, lat)
cells = m3s.Maidenhead.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.Maidenhead.fromPoint(2.35, 48.86);            // (lon, lat)
const cells = m3s.Maidenhead.fromBbox([2.2, 48.8, 2.4, 48.9]); // bbox
console.log(cell.id, cells.length);

from _deckmap import DeckExplorer, read_grid_js


DeckExplorer(
    center=(9.5, 48.5),
    zoom=5,
    grid_js=read_grid_js("maidenhead"),
    hover="#882255",
    wasm=True,
)