node-geohash

Geohash library for nodejs.

Install

npm install ngeohash

Usage

var geohash = require('ngeohash');
console.log(geohash.encode(37.8324, 112.5584));
// prints ww8p1r4t8
var latlon = geohash.decode('ww8p1r4t8');
console.log(latlon.latitude);
console.log(latlon.longitude);

Basic Methods

geohash.encode (latitude, longitude, precision=9)

Encode a pair of latitude and longitude values into a geohash. The third argument is optional, you can specify a length of this hash string, which also affects the precision of the geohash.

geohash.decode (hashstring)

Decode a hash string into pair of latitude and longitude values. A javascript object is returned with latitude and longitude keys.

geohash.decode_bbox (hashstring)

Decode hashstring into a bounding box that matches it. Data is returned as a four-element array: [minlat, minlon, maxlat, maxlon].

geohash.bboxes (minlat, minlon, maxlat, maxlon, precision=9)

Get all hashstringes between [minlat, minlon] and [maxlat, maxlon]. These keys can be used to find a poi stored in the cache with hashstring keys. eg. show all points in the visible range of map. [minlat, minlon] correspond to the southwest starting hash, whereas [maxlat, maxlon] correspond to the northeast starting hash.

geohash.neighbor (hashstring, direction)

Find the neighbor of a geohash string in certain direction. Direction is a two-element array, i.e. [1,0] means north, [-1,-1] means southwest.

geohash.neighbors (hashstring)

Find all 8 geohash neighbors [n, ne, e, se, s, sw, w, nw] of a geohash string. This method is more efficient than running the geohash.neighbor method multiple times for all directions. array: [hashstr1, hashstr2, ... ]

Integer Methods

Note that integer precision is capped at 52bits in Javscript. These are just regular javascript floating point numbers, but the functionality should mimic other uint64 geohash functions in geohash libraries for other languages and are compatible with the geohash integers produced by them, however any geohash integer encoded in anything more than 52bits will be resolved to 52bits resolution.

geohash.encode_int (latitude, longitude, bitDepth=52)

Encode a pair of latitude and longitude values into a geohash integer. The third argument is optional, you can specify the bitDepth of this number, which affects the precision of the geohash but also must be used consistently when decoding. Bit depth must be even.

geohash.decode_int (hashinteger, bitDepth=52)

Decode a integer geohashed number into pair of latitude and longitude value approximations. A javascript object is returned with latitude and longitude keys. You should also provide the bitDepth at which to decode the number (ie. what bitDepth the number was originally produced with), but will default to 52.

geohash.decode_bbox_int (hashinteger, bitDepth=52)

Decode an integer geohash into the bounding box that matches it. Data is returned as a four-element array: [minlat, minlon, maxlat, maxlon].

geohash.bboxes_int (minlat, minlon, maxlat, maxlon, bitDepth=52)

Get all geohash integers between [minlat, minlon] and [maxlat, maxlon]. These keys can be used to find a poi stored in the cache with geohash integer keys. eg. show all points in the visible range of map

geohash.neighbor_int (hashinteger, direction, bitDepth=52)

Find the neighbor of a geohash integer in certain direction. Direction is a two-element array, i.e. [1,0] means north, [-1,-1] means southwest. The bitDepth should be specified, but defaults to 52 bits.

geohash.neighbors_int (hashinteger, bitDepth=52)

Find all 8 neighbors [n, ne, e, se, s, sw, w, nw] of a geohash integer. This method is more efficient than running the geohash.neighbor method multiple times for all directions. The bitDepth should be specified, but defaults to 52 bits.

Node-Geohash for browser

We recently added a browserify script with npm run browserify. ngeohash.js will be generated and you can use this file in your javascript application for browser.

<script src="./path/to/ngeohash.js"></script>
<script>
alert(ngeohash.encode(114.23, 38.23));
</script>

About Geohash

Check Wikipedia for more information.

See Also

Geohash.rs: node-geohash ported to Rust: A rust library for geohash.

License

node-geohash is open sourced under MIT License, of course.

Donation

I'm now accepting donation on liberapay, if you find my work helpful and want to keep it going.