geojson2h3

The geojson2h3 library includes a set of utilities for conversion between GeoJSON polygons and H3 hexagon indexes, using h3-js.

• Post bug reports or feature requests to the Github Issues page
• Ask questions by posting to the H3 tag on StackOverflow

Installation

npm install geojson2h3

Example Usage

import geojson2h3 from 'geojson2h3';

const polygon = {
  type: 'Feature',
  geometry: {
    type: 'Polygon',
    coordinates: [[
      [-122.47485823276713, 37.85878356045377],
      [-122.47504834087829, 37.86196795698972],
      [-122.47845104316997, 37.86010614563313],
      [-122.47485823276713, 37.85878356045377]
    ]]
  }
};

const hexagons = geojson2h3.featureToH3Set(polygon, 10);
// -> ['8a2830855047fff', '8a2830855077fff', '8a283085505ffff', '8a283085506ffff']

const feature = geojson2h3.h3SetToFeature(hexagons);
// -> {type: 'Feature', properties: {}, geometry: {type: 'Polygon', coordinates: [...]}}

API Reference

geojson2h3

• geojson2h3
  • .featureToH3Set(feature, resolution) ⇒ Array.<String>
  • .h3ToFeature(hexAddress, [properties]) ⇒ Feature
  • .h3SetToFeature(hexagons, [properties]) ⇒ Feature
  • .h3SetToMultiPolygonFeature(hexagons, [properties]) ⇒ Feature
  • .h3SetToFeatureCollection(hexagons, [getProperties]) ⇒ FeatureCollection

---

geojson2h3.featureToH3Set(feature, resolution) ⇒ Array.<String>

Convert a GeoJSON feature to a set of hexagons. Only hexagons whose centers fall within the feature will be included. Note that conversion from GeoJSON is lossy; the resulting hexagon set only approximately describes the original shape, at a level of precision determined by the hexagon resolution.

If the polygon is small in comparison with the chosen resolution, there may be no cell whose center lies within it, resulting in an empty set. To fall back to a single H3 cell representing the centroid of the polygon in this case, use the ensureOutput option.

Kind: static method of geojson2h3
Returns: Array.<String> - H3 indexes

Param	Type	Description
feature	Object	Input GeoJSON: type must be either Feature or FeatureCollection, and geometry type must be either Polygon or MultiPolygon
resolution	Number	Resolution of hexagons, between 0 and 15
[options.ensureOutput]	Boolean	Whether to ensure that at least one cell is returned in the set

---

geojson2h3.h3ToFeature(hexAddress, [properties]) ⇒ Feature

Convert a single H3 hexagon to a Polygon feature

Kind: static method of geojson2h3
Returns: Feature - GeoJSON Feature object

Param	Type	Description
hexAddress	String	Hexagon address
[properties]	Object	Optional feature properties

---

geojson2h3.h3SetToFeature(hexagons, [properties]) ⇒ Feature

Convert a set of hexagons to a GeoJSON Feature with the set outline(s). The feature's geometry type will be either Polygon or MultiPolygon depending on the number of outlines required for the set.

Kind: static method of geojson2h3
Returns: Feature - GeoJSON Feature object

Param	Type	Description
hexagons	Array.<String>	Hexagon addresses
[properties]	Object	Optional feature properties

---

geojson2h3.h3SetToMultiPolygonFeature(hexagons, [properties]) ⇒ Feature

Convert a set of hexagons to a GeoJSON MultiPolygon feature with the outlines of each individual hexagon.

Kind: static method of geojson2h3
Returns: Feature - GeoJSON Feature object

Param	Type	Description
hexagons	Array.<String>	Hexagon addresses
[properties]	Object	Optional feature properties

---

geojson2h3.h3SetToFeatureCollection(hexagons, [getProperties]) ⇒ FeatureCollection

Convert a set of hexagons to a GeoJSON FeatureCollection with each hexagon in a separate Polygon feature with optional properties.

Kind: static method of geojson2h3
Returns: FeatureCollection - GeoJSON FeatureCollection object

Param	Type	Description
hexagons	Array.<String>	Hexagon addresses
[getProperties]	function	Optional function returning properties for a hexagon: f(h3Index) => Object

---

Development

The geojson2h3 library uses yarn as the preferred package manager. To install the dev dependencies, just run:

yarn

To run the tests in both native ES6 (requires Node >= 6) and transpiled ES5:

yarn test

To format the code:

yarn prettier

To rebuild the API documentation in the README file:

yarn build-docs

Contributing

Pull requests and Github issues are welcome. Please include tests for new work, and keep the library test coverage at 100%. Before we can merge your changes, you must agree to the Uber Contributor License Agreement.

Legal and Licensing

The geojson2h3 library is licensed under the Apache 2.0 License.