geojson2h3

README

go-geojson2h3

The geojson2h3 library includes a set of utilities for conversion between GeoJSON Objects:

• Point, MultiPoint,
• LineString, MultiLineString
• Polygon,MultiPolygon
• GeometryCollection
• Feature,FeatureCollection
• Circle

and H3 hexagon indexes, using: H3-GO and GeoJSON

Installation

$ go get github.com/mmadfox/go-geojson2h3

API

// ToH3 converts a GeoJSON objects to a list of hexagons with specified resolution.
ToH3(resolution int, o geojson.Object) (indexes []h3.H3Index, err error)

// ToFeatureCollection converts a set of hexagons to a GeoJSON `FeatureCollection`
// with the set outline(s). The feature's geometry type will be `Polygon`.
ToFeatureCollection(indexes []h3.H3Index) (*geojson.FeatureCollection, error)

Examples

• Point, MultiPoint
• LineString, MultiLineString
• Polygon,MultiPolygon
• GeometryCollection
• Feature,FeatureCollection
• Circle
• Rect

package main

import (
	"fmt"

	"github.com/mmadfox/go-geojson2h3"
	"github.com/tidwall/geojson"
	"github.com/uber/h3-go/v3"
)

func main() {
	resolution := 9
	object, err := geojson.Parse(`{"type":"FeatureCollection","features":[{"type":"Feature","properties":{"shape":"Polygon","name":"Unnamed Layer","category":"default"},"geometry":{"type":"Polygon","coordinates":[[[-73.901303,40.756892],[-73.893924,40.743755],[-73.871476,40.756278],[-73.863378,40.764175],[-73.871444,40.768467],[-73.879852,40.760014],[-73.885515,40.764045],[-73.891522,40.761054],[-73.901303,40.756892]]]},"id":"a6ca1b7e-9ddf-4425-ad07-8a895f7d6ccf"}]}`, nil)
	if err != nil {
		panic(err)
	}

	indexes, err := geojson2h3.ToH3(resolution, object)
	if err != nil {
		panic(err)
	}
	for _, index := range indexes {
		fmt.Printf("h3index: %s\n", h3.ToString(index))
	}

	featureCollection, err := geojson2h3.ToFeatureCollection(indexes)
	if err != nil {
		panic(err)
	}
	fmt.Println("Polyfill:")
	fmt.Println(featureCollection.JSON())
}

Contributing

Pull requests and Github issues are welcome. Please include tests for new work, and keep the library test coverage at 90-100%.

Documentation

Index

• func ToFeatureCollection(indexes []h3.H3Index) (*geojson.FeatureCollection, error)
• func ToH3(resolution int, o geojson.Object) (indexes []h3.H3Index, err error)

Functions

func ToFeatureCollection

func ToFeatureCollection(indexes []h3.H3Index) (*geojson.FeatureCollection, error)

ToFeatureCollection converts a set of hexagons to a GeoJSON `FeatureCollection` with the set outline(s). The feature's geometry type will be `Polygon`.

func ToH3

func ToH3(resolution int, o geojson.Object) (indexes []h3.H3Index, err error)

ToH3 converts a GeoJSON objects to a list of hexagons with specified resolution.

Known list of objects:

• Point, MultiPoint
• Line, MultiLine
• Polygon, MultiPolygon
• GeometryCollection
• Feature, FeatureCollection

Extended GeoJSON library:

• Rect, Circle, SimplePoint

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.