Store and retrieve places near a lat/long pair, using leveldb
npm install level-placesStore and retrieve places near a lat/long pair, using
leveldb.
Given a location, get all the nearby places, starting with the nearest one:
``js
var level = require('level');
var Places = require('level-places');
var places = Places(level(__dirname + '/db'));
places.add('Kaufbeuren', 47.8800, 10.6225);
places.add('New York', 40.7142, -74.0064);
places.createReadStream(47.8838, 10.6171, { limit: 1 })
.on('data', console.log);
// => "Kaufbeuren"
`
Lat/long pairs are serialized into
geohashes. The geohash for
(47.8800, 10.6225) for example is u0x83sr14nyj. In order to query places
efficiently this makes use of the fact that geohashes of geographically
adjacent places start with the same characters, so they sort well.
When querying for (47.8800, 10.6225)/u0x83sr14nyj, level-places queries
its database using those keys:
* u0x83sr14nyj
*
*
*
*
*
*
*
*
*
*
*
So, every place is stored redundantly under each of those keys. When a limit
is given and it is reached, level-store stops going further down the list.
Return a level-places instance that uses db for its storage, which needs
to be an instance of levelup.
If you want to store other data in db, use
level-sublevel to pass a
subsection of your database.
Add place to the given lat/long pair. place can be of any type thatJSON.stringify accepts. Optionally call fn as soon as the place was
saved to the db.
Create a readable stream that emits places around the provided lat/long pair,
starting with the nearest one.
Possible options are:
* limit: Limit the result set to x places.
With npm do
`bash``
$ npm install level-places
Copyright (c) 2013 Julian Gruber <julian@juliangruber.com>
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