Awesome

geohash-point-store

Store and query spatial points using geohashes and LevelDB.

Uses geohashing to index points for fast storage and querying.

Usage

var Geostore = require('geohash-point-store')
var memdb = require('memdb')

var levelDb = memdb()
var store = Geostore(levelDb)

var n = 1000
var spread = 0.2  // 0.2 of lat/lon is about 20km
var pending = n
function insert () {
  if (!--pending) return query()
  var x = 0.3 + Math.random() * spread - spread/2
  var y = 0.3 + Math.random() * spread - spread/2
  var value = Math.random().toString().substring(2, 4)
  db.insert([x, y], value, insert)
}
insert()

function query () {
  var at = [0.3, 0.3]
  var q = db.queryStream(at, 1)  // 1km
  q.on('data', function (pt) {
    console.log('Q', pt)
  })
}

outputs

Q { lat: 0.29634207747112706, lon: 0.2993872801415114, value: '38' }
Q { lat: 0.3068307609860095, lon: 0.295966883616435, value: '73' }
Q { lat: 0.2981759863251534, lon: 0.29876116341017966, value: '78' }
Q { lat: 0.3029278595931988, lon: 0.2977136462590203, value: '57' }

API

var Geostore = require('geohash-point-store')

var store = Geostore(db)

Create a new point store, using the LevelUP instance db for storage.

store.insert(pt, value, cb)

Insert value (and JSON serializable object) at point pt. pt must be an array of the form [latitude, longitude].

var readstream = store.queryStream(at, distance)

Query for all points around point at (an array of [lat, lon]) that are within distance distance, in kilometres.

Returns a readable stream of points of the form { lat: ?, lon: ?, value: ? }.

Caveats

only one point is stored at a precise geohash, so multiple close points (within metres) could overwrite each other

Install

With npm installed, run

$ npm install geohash-point-store

License

ISC