vector-tile-query

vector-tile-query 1.2.0

vector-tile-query allows you to query Mapbox Vector Tiles and return data values from these tiles. This module consists of one main function, and two utility / helper functions.

queryTile(<pbuf>, <tileInfo>, <queryPoints>, <pointIDs>, <options>, <callback>);

Parses a Vector Tile protobuf and queries a layer for a a number of fields based on a series of lat, lngs points

Input

• pbuf: vector tile (pbuf)
• tileInfo: tile Z,X,Y ('tileinfo: {z:,x:,y:}')
• queryPoints: array of lat, lngss ([[lat,lng],[lat,lng]...])
• pointIDs: array of point IDs that correspond to order of query lat,lngs ([0,1,2...])
• options: options for query:
• layer: layer within the tile source to query. Example: contour
• fields: array of fields within the layer to return data for. Example [ele]
• interpolate (optional): whether or not to interpolate between closest two features. Example false. Default true
• callback: function(err,data) {...} to call upon completion of query

Output

Array (with one record per input lat,lng) of values:

[
    {
        id: <id>,
        latlng: { lat: <lat>, lng: <lng> },
        <field1>: <field1 value>,
        <field2>: <field2 value>
    },
    ...
]

loadTiles(<queryPoints>, <zoom>, <loadFunction>, <callback>)

Given a set of lat,lng points and a zoom level, finds what tiles to load, loads these tiles asynchronously (using a defined function), splits query lat, lngss out per tile, and assigns these a sequential ID (based on input order)

Input

• queryPoints: array of lat, lngss ([[lat,lng],[lat,lng]...])
• zoom: zoom level of tiles to query
• loadFunction: function to load tiles / should return a pbuf
• callback: function(err,data) {...} to call upon completion

Output

Array of "tile objects" with tile zxy, query points within that tile, ids of these points, and vector tile pbufs.

[
    {
        zxy: { z: <z>, x: <x>, y: <y> },
        points: [ [lat,lng], [lat,lng], ... ],
        pointIDs: [ 0, 1, ... ],
        data: <vtile pbuf>
    } 
...
]

multiQuery(dataArr,options,callback)

Helper function to asynchronously query (using queryTile (given a set of "tile objects") and return sorted values (based on input order / input point ids).

Input

• dataArr: array of "tileObjects" as described above - one record for each tile that will be queried
• options: options as described above in queryTile
• callback: function(err,data) {...} to call upon completion

Output

Array (with one record per input lat,lng) of values:

[
    {
        id: <id>,
        latlng: { lat: <lat>, lng: <lng> },
        <field1>: <field1 value>,
        <field2>: <field2 value>
    },
    ...
]

Usage

git clone https://github.com/mapbox/vector-tile-query.git
npm install