vector-tile-esm v2.1.4

vector-tile-esm

Reads Mapbox Vector Tiles and allows access to the layers and features.

This module is a fork of vector-tile-js, with several key changes:

• Code is set up for ESM import, rather than CJS require. This allows it to be imported dynamically (e.g., on Observable) without depending on a third-party bundling service such as bundle.run
• The VectorTileFeature.toGeoJSON() method behaves very differently, returning pixel coordinates within a tile, rather than assuming Web Mercator and attempting to back-project to longitude and latitude
• The dependence on the point-geometry module has been removed

Example

import { VectorTile } from 'vector-tile-esm';
import Protobuf from 'pbf-esm';

var tile = new VectorTile(new Protobuf(data));

// Contains a map of all layers
tile.layers;

var landuse = tile.layers.landuse;

// Number of features in this layer
landuse.length;

// Returns the first feature
landuse.feature(0);

API Reference

vector-tile-esm exposes 3 constructors: VectorTile, VectorTileLayer, and VectorTileFeature.

VectorTile

An object that parses vector tile data and makes it readable.

Constructor

• new VectorTile(protobuf, end) — parses the vector tile data contained in the given Protobuf object, saving resulting layers in the created object as a layers property. Optionally accepts end index.

Properties

• layers (Object) — an object containing parsed layers in the form of {<name>: <layer>, ...}, where each layer is a VectorTileLayer object.

VectorTileLayer

An object that contains the data for a single vector tile layer.

Properties

• version (Number, default: 1)
• name (String)— layer name
• extent (Number, default: 4096) — tile extent size
• length (Number) — number of features in the layer

Methods

• feature(i) — get a feature (VectorTileFeature) by the given index from the layer.
• toGeoJSON(size, sx, sy) — Return a GeoJSON FeatureCollection representing all the features in the layer. See the corresponding method of VectorTileFeature for the parameters

VectorTileFeature

An object that contains the data for a single feature.

Properties

• type (Number) — type of the feature (also see VectorTileFeature.types)
• extent (Number) — feature extent size
• id (Number) — feature identifier, if present
• properties (Object) — object literal with feature properties

Methods

• loadGeometry() — parses feature geometry and returns an array of point objects, with each point having x and y properties
• bbox() — calculates and returns the bounding box of the feature in the form [x1, y1, x2, y2]
• toGeoJSON(size, sx, sy) — returns a GeoJSON representation of the feature.
  • size — side length of the (square) area over which the tile's features will be rendered. Default: the .extent property of the layer
  • sx, sy — optionally specify the origin of the output coordinates within the (size x size) rendered area of the full tile.