h3-to-geojson

A lightweight utility library for converting H3 cells to GeoJSON features and geometries, along with additional tools for working with the H3 geoindexing system.

Features

• Convert H3 cells to GeoJSON Point and Polygon features or geometries.
• Convert coordinates to H3 cells and vice versa.
• Retrieve H3 cells contained within a GeoJSON Polygon or MultiPolygon.
• Calculate the bounding box (BBox) of an H3 cell.
• Get the resolution of an H3 cell.

Installation

Install the library:

npm install h3-to-geojson

or

pnpm add h3-to-geojson

Usage

Here is an example of how to use the library:

import {
  coordToH3,
  h3ToCoord,
  h3ToPointFeature,
  h3ToPolygonFeature,
  getH3InsideGeoJSON,
} from 'h3-to-geojson';

// Convert coordinates to an H3 cell
const coord = [-3.6886, 40.4201]; // Madrid [longitude, latitude]
const resolution = 9;
const h3Cell = coordToH3(coord, resolution);
console.log('H3 Cell:', h3Cell);

// Convert an H3 cell back to coordinates
const backToCoord = h3ToCoord(h3Cell);
console.log('Coordinates:', backToCoord);

// Convert an H3 cell to a GeoJSON Point feature
const pointFeature = h3ToPointFeature(h3Cell);
console.log('GeoJSON Point Feature:', pointFeature);

// Convert an H3 cell to a GeoJSON Polygon feature
const polygonFeature = h3ToPolygonFeature(h3Cell);
console.log('GeoJSON Polygon Feature:', polygonFeature);

// Retrieve all H3 cells inside a GeoJSON Polygon
const geojsonPolygon = {
  type: 'Polygon',
  coordinates: [
    [
      [-3.700647, 40.404397],
      [-3.700647, 40.43498],
      [-3.667943, 40.43498],
      [-3.667943, 40.404397],
      [-3.700647, 40.404397],
    ],
  ],
};
const h3Cells = getH3InsideGeoJSON(geojsonPolygon, resolution);
console.log('H3 Cells inside the GeoJSON Polygon:', h3Cells);

Documentation

See DOCS

License

This project is licensed under the MIT License.

Acknowledgements

• Built on top of the H3-js library.
• GeoJSON utilities powered by @turf/helpers.