GARS grid

Global Area Reference System — a worldwide 30-minute cell grid (refinable to 15 and 5 minutes) used by defence and air operations for area reference.

The interactive explorer below is rendered with deck.gl and behaves like the h3geo.org map: the GARS precision follows the zoom and cells 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 quadrant/keypad nesting stays visible. The band/zone/quadrant/keypad encoder is the exact one in m3s.gars, reproduced in JavaScript so the cell ids and edges match M3S. GARS only goes as coarse as 30′ (0.5°) — there is no coarser cell — so a full-globe vector grid (259k cells) is impractical; the demo opens over France and the zoom is floored so the grid stays visible however far you zoom out. GIS-native (lon, lat) order is used throughout.

Why GARS?

GARS exists to be said over a radio: a fixed worldwide 30-minute grid with two refinements (15′ quadrants, 5′ keypads), adopted so that air and ground units from different services reference the same area with the same short code. If that is your context, nothing else fits. Outside it, GARS has little to offer — three coarse levels, latitude-stretched rectangles, no fine precision. Use MGRS grid when you need metre-level field coordinates, or EA-Quad grid for actual area analysis.

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.GARS.from_geometry((2.35, 48.86))            # (lon, lat)
cells = m3s.GARS.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.GARS.fromPoint(2.35, 48.86);            // (lon, lat)
const cells = m3s.GARS.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=(2.5, 46.8), zoom=7, grid_js=read_grid_js("gars"), hover="#DDCC77", wasm=True
)