https://github.com/hackergrrl/geohash-point-store

:earth_asia: Store and query spatial points using geohashes and LevelDB.
https://github.com/hackergrrl/geohash-point-store

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:earth_asia: Store and query spatial points using geohashes and LevelDB.

• Host: GitHub
• URL: https://github.com/hackergrrl/geohash-point-store
• Owner: hackergrrl
• Created: 2017-08-13T19:33:09.000Z (about 7 years ago)
• Default Branch: master
• Last Pushed: 2017-08-23T16:44:56.000Z (about 7 years ago)
• Last Synced: 2024-08-17T08:27:13.686Z (about 2 months ago)
• Language: JavaScript
• Homepage:
• Size: 6.84 KB
• Stars: 6
• Watchers: 2
• Forks: 1
• Open Issues: 3
• Metadata Files:
  • Readme: README.md

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README

        
# geohash-point-store

> Store and query spatial points using geohashes and LevelDB.

Uses [geohashing](https://en.wikipedia.org/wiki/Geohash) to index points for

fast storage and querying.

## Usage

```js

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

```js

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

```

### var store = Geostore(db)

Create a new point store, using the

[LevelUP](https://www.npmjs.com/package/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](https://npmjs.org/) installed, run

```

$ npm install geohash-point-store

```

## See Also

- [level-places](https://github.com/Wayla/level-places)

- [kdb-tree-store](https://github.com/peermaps/kdb-tree-store)

## License

ISC