query-mvt

Query map features nearest to a given point from a remote MVT vector tiles layer


query-mvt allows you query remote vector tile sets for features. Its main advantage is that it does not require any special access or server-side software as it mimics the behavior of a web browser displaying the map.

It works both in Node.js and in the browser. It supports all vector mapping services that use MVT/PBF files and can adapt to different projections and tileset extents.

Usage

``shell
npm i query-mvt
`

Vector tile sets created by GDAL and a few other tools come with a de-facto standard metadata.json that allows query-mvt to automatically acquire all the needed parameters (such as map projects, tile grid and size, world bounds):

with metadata.json

`js
import * as queryMVT from 'query-mvt';

// Automatically imports the layer metadata
// (EPSG:4326 with world coverage in this case)
queryMVT.acquire('https://velivole.b-cdn.net/tiles/place/2/metadata.json')
.then((metadata) => queryMVT.search({
url: 'https://velivole.b-cdn.net/tiles/place/2/{z}/{x}/{y}.pbf',
lon: 6.220432,
lat: 45.779170,
metadata
}))
.then((result) => {
assert.strictEqual(result.feature.properties['n'], 'Doussard');
assert.closeTo(result.distance, 0.34, 0.1);
})
`

raw MVT tiles

Most commercial public mapping services such as Qwant do not have a metadata.json but tend to use the same EPSG:3857 projection (aka Web Mercator) and world bounds:

`js
import * as queryMVT from 'query-mvt';

// Configure manually the layer metadata
// (EPSG:3857 with world coverage in this case)
queryMVT.search({
url: 'https://tiles.qwant.com/default/{z}/{x}/{y}',
lon: 2.348942,
lat: 48.853289,
// You can filter the results
filter: (f) => f.properties['class'] === 'city',
maxFeatures: 20,
maxRadius: 10,
metadata: queryMVT.constants.EPSG3857
})
.then((results) => {
assert.strictEqual(results[0].feature.properties['class'], 'city');
assert.strictEqual(results[0].feature.properties['name'], 'Paris');
assert.closeTo(results[0].distance, 0.04, 0.1);
})
`

CLI

A stand-alone CLI version exists as well:

`shell


Query the nearest village near 45.779° N : 6.22° E


query-mvt 45.779 6.22 -f class=village
`

API

#### Table of Contents

* Result
* Properties
* distance
* feature
* acquire
* Parameters
* search
* Parameters

$3

Type: {distance: number, feature: turf.Feature}

#### Properties

* distance number
* feature turf.Feature

#### distance

Distance in km

Type: number

#### feature

Feature (turf.js and GeoJSON compatible)

Type: turf.Feature

$3

#### Parameters

* url string URL of a GDAL-style metadata.json
* fetchOpts RequestInit? optional fetch options (AbortController, authorization headers...)

Returns MVTMetadata

$3

#### Parameters

* opts Record<string, any> options

* opts.url string Openlayers-style URL template for requesting tiles, must contain {x}, {y} and {z}
* opts.metadata MVTMetadata? optional GDAL-style metadata.json, may be empty for world-wide EPSG:3857 tilesets
* opts.lon number longitude
* opts.lat number latitude
* opts.queue Queue? optional shared Queue to be used for limiting concurrency, @default Queue(8,0)
* opts.maxFeatures number? optional number of features to return, @default 1
* opts.maxRadius number? optional maximum radius in km to search in, @default 10
* opts.fetchOpts RequestInit? optional fetch options (AbortController, authorization headers...)
* opts.dedupe` boolean? dedupe the returned features (as the text will usually stretch across several tiles)

Returns Promise<Array<Result>>