@parellin/geohash

Geohash decode/encoder

Precision	Width	Height
1	≤ 5,000km	× 5,000km
2	≤ 1,250km	× 625km
3	≤ 156km	× 156km
4	≤ 39.1km	× 19.5km
5	≤ 4.89km	× 4.89km
6	≤ 1.22km	× 0.61km
7	≤ 153m	× 153m
8	≤ 38.2m	× 19.1m
9	≤ 4.77m	× 4.77m
10	≤ 1.19m	× 0.596m
11	≤ 149mm	× 149mm
12	≤ 37.2mm	× 18.6mm

Installation

npm i @parellin/geohash

Usage

Basic usage:

const Geohash = require( '@parellin/geohash' );
const hash = Geohash.encode( -77.480, 38.866, 7 ); // hash: 'dqbvhgk'

encode

Encodes longitude/latitude to geohash, either to specified precision or to automatically evaluated precision.

params

• lng {number} Longitude in degrees.
• lat {number} Latitude in degrees.
• precision {number} Number of characters in resulting geohash.

returns: Geohash of supplied longitude/latitude.

const hash = Geohash.encode( -77.480, 38.866, 7 ); // hash: 'dqbvhgk'

decode

Decode geohash to longitude/latitude (location is approximate center of geohash cell, to reasonable precision).

params

• geohash {string} Geohash string to be converted to longitude/latitude.

returns: (Center of) geohashed location.

const latlng = Geohash.decode( 'dqbvhgk' ); // latlng: { lng: -77.4804, lat: 38.8662 }

neighbors

Returns 8 adjacent cells to specified geohash.

params

• geohash {string} Geohash to find neighbors of.
• asObject {boolean} return geohashes in an object ({c,n,ne,e,se,s,sw,w,nw})

returns: surrounding geohashes

const latlng = Geohash.neighbors( 'dqcjpxetzh6q' );
[
	'dqcjpxetzh6r', 'dqcjpxetzh6x', 'dqcjpxetzh6w', 'dqcjpxetzh6t',
	'dqcjpxetzh6m', 'dqcjpxetzh6j', 'dqcjpxetzh6n', 'dqcjpxetzh6p'
]

Example:

Geohash.neighbors( 'dqcjpxetzh6q' );

           ┬────────────────────────────────────────────────────┐
           │      'west'          'center'         'east'       │
┼──────────┼────────────────────────────────────────────────────┤
│ 'north'  │   'dqcjpxetzh6p'  'dqcjpxetzh6r'  'dqcjpxetzh6x'   │
│ 'center' │   'dqcjpxetzh6n'  'dqcjpxetzh6q'  'dqcjpxetzh6w'   │
│ 'south'  │   'dqcjpxetzh6j'  'dqcjpxetzh6m'  'dqcjpxetzh6t'   │
┴──────────┴────────────────────────────────────────────────────┘

GeohashStream

GeohashStream takes in a BBox and streams geohashes within that bbox.

params

• minLng {number} bbox min longitude
• minLat {number} bbox min latitude
• maxLng {number} bbox max longitude
• maxLat {number} bbox max latitude
• precision {number=7} geohash precision (defaults to 7)

new Geohash.GeohashStream( 0.1, 52.2, 0.2, 52.3, 3 )
	.on( 'data', d => console.log( d.toString() ) )
	.on( 'end', () => console.log( 'done' ) );

// u12

GeohashStreamGeoJSON

GeohashStreamGeoJSON is the same as GeohashStream but streams back GeoJSON

params

• minLng {number} bbox min longitude
• minLat {number} bbox min latitude
• maxLng {number} bbox max longitude
• maxLat {number} bbox max latitude
• precision {number=7} geohash precision (defaults to 7)

new Geohash.GeohashStreamGeoJSON( 0.1, 52.2, 0.2, 52.3, 3 )
	.on( 'data', d => console.log( d.toString() ) )
	.on( 'end', () => console.log( 'done' ) );

// {
// 	"type": "Feature",
// 	"bbox": [ 0, 52.03125, 1.40625, 53.4375 ],
// 	"properties": {},
// 	"geometry": {
// 		"type": "Polygon",
// 		"coordinates": [ [
// 			[ 0, 52.03125 ],
// 			[ 1.40625, 52.03125 ],
// 			[ 1.40625, 53.4375 ],
// 			[ 0, 53.4375 ],
// 			[ 0, 52.03125 ]
// 		] ]
// 	}
// }