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    level-geospatial

    0.0.6 • Public • Published

    level-geospatial

    Uses a quadtree to index latitude and longitude coordinates in a leveldb database.

    NPM

    Project Status

    Experimental - subject to change.

    Install

    $ npm install level-geospatial
    

    How to use

    The module takes a leveldb database (or a sub-level):

    var db = require('level')('path_to_your_database');
    var geo = require('level-geospatial')(db);

    You can then start adding key/values, along with latitude/longitude values.

    // lat, lon, key, value 
    geo.put({lat:52.081959, lon:1.415904}, 'Location1', 'My value', function(err){
    	if (err) console.log(err);
    });

    You can retrieve a value back like this:

    // this is the fast way of getting the value
    geo.get({lat:52.081959, lon:1.415904}, 'Location1',function(err,data){
    	console.log(data);
    });
    
    // this is the slower/convenient way of getting the value
    geo.getByKey('Location1', function(err,data){
    	console.log(data);
    });
    
    // the data returned looks like this:
    { quadKey: '1222222212112112222210',
      position: {
        lat: 52.081959,    
        lon: 1.415904 },
      id: 'Location1',
      value: 'My value' }

    You can search within a radius (in meters) of a given point:

    // lat, lon, radius in meters
    geo.search({lat:52.081959, lon:1.415904}, 15000).on('data', function(data){
    	console.log(data)
    });
    
    // the data returned looks like this:
    { quadKey: '1222222212112112222210',
      position: {
        lat: 52.081959,    
        lon: 1.415904 },
      id: 'Location1',
      value: 'My value',
      distance: 1232.232323 }  // this is the distance in meters from your search

    Please note, the results are not returned in any meaningful order.

    You can update/delete like this:

    // to update the value/location:
    geo.put({lat:53.1, lon:2.2}, "Location1", "NEW VALUE", function(err){
    	if (err) console.log(err);
    });
    
    // to delete
    geo.del("Location1", function(err){
    	if (err) console.log(err);
    });

    How does it work?

    The data is indexed using a quadtree. When you index a point, it's quadkey is calculated to a depth of 22.

    The quadkey is a string which stores where the point lives in the quadtree. The quadkey notation used is the same as Bing Maps. The quadkeys can be inserted into this URL to retrieve a map tile for a given location:

    http://ak.dynamic.t1.tiles.virtualearth.net/comp/ch/{QUADKEY}?mkt=en-gb&it=G,VE,BX,L,LA&shading=hill&og=18&n=z
    

    When you search the database, the quadkey is calculated for search location. The radius is then used to calculate an appropriate depth in the quadtree to search to.

    Potential matches within those quads are then tested using a simple distance calculation to work out if they are close enough to be included in the results.

    TODO

    Currently searches that span the international date line will not return all results. Batch operations are not supported.

    License

    MIT

    Install

    npm i level-geospatial

    DownloadsWeekly Downloads

    15

    Version

    0.0.6

    License

    MIT

    Unpacked Size

    26.4 kB

    Total Files

    9

    Last publish

    Collaborators

    • richard.astbury