GeoJSONTiler

The GeoJSONTiler slices large GeoJSON data into small vector tiles on the fly.

The primary intended use case is to enable rendering and interacting with large geospatial datasets in the browser (without requiring data to be pre-tiled and tiles to be served from a server).

The resulting tiles conform to the JSON output of the MVTLoader (which loads pre-tiled tiles in the vector tile specification into GeoJSON format).

To make data rendering and interaction fast, the GeoJSON content in the generated tiles is not only cut out from the larger input GeoJSON. It are also optimized further to only retain the minimum level of detail appropriate for each zoom level (shapes are simplified and tiny polygons and line segments are filtered out).

Install

Install using NPM (npm install @loaders.gl/mvt) or Yarn (yarn install @loaders.gl/mvt).

TBD - Or use a browser build directly:

<script src="https://unpkg.com/@loaders.gl/mvt/dist.min.js"></script>

Usage

import {GeoJSONTiler} from '@loaders.gl/mvt';

// build an initial index of tiles
const tileSource = new GeoJSONTiler(geoJSON);

// request a particular tile
const features = tileSource.getTile(z, x, y).features;

// show an array of tile coordinates created so far
console.log(tileSource.tileCoords); // [{z: 0, x: 0, y: 0}, ...]

Options

You can fine-tune the results with an options object, although the defaults are sensible and work well for most use cases.

Option	Default	Description
indexMaxZoom	5	Max zoom in the initial tile index
indexMaxPoints	100000	Max number of points per tile in the index
maxZoom	14	Max zoom to preserve detail on; can't be higher than 24
tolerance	3	Simplification tolerance (higher means simpler)
extent	4096	tile extent (both width and height)
buffer	64	Tile buffer on each side
promoteId	N/A	Name of a feature property to use for feature.id.
generateId	false	Whether to generate feature ids.
debug	0	Logging level (0 to disable, 1 or 2)
lineMetrics	false	Enable line metrics tracking for LineString/MultiLineString features

import {GeoJSONTiler} from '@loaders.gl/mvt`
const tileSource = new GeoJSONTiler(parsedGeojson, {
	indexMaxZoom: 5,  // max zoom in the initial tile index
	maxZoom: 14,      // max zoom to preserve detail on; can't be higher than 24
	tolerance: 3,     // simplification tolerance (higher means simpler)
	extent: 4096,     // tile extent (both width and height)
	buffer: 64,   // tile buffer on each side
	debug: 0,     // logging level (0 to disable, 1 or 2)
	lineMetrics: false, // whether to enable line metrics tracking for LineString/MultiLineString features
	promoteId: null,    // name of a feature property to promote to feature.id. Cannot be used with `generateId`
	generateId: false,  // whether to generate feature ids. Cannot be used with `promoteId`
	indexMaxPoints: 100000 // max number of points per tile in the index
});

Remarks:

• GeoJSONTiler only operates on zoom levels up to 24.
• generateId and promoteId cannot both be specified at the same time.
• The promoteId and generateId options ignore existing id values on the feature objects.
• By default, tiles at zoom levels above indexMaxZoom are generated on the fly, but you can pre-generate all possible tiles for data by setting indexMaxZoom and maxZoom to the same value, setting indexMaxPoints to 0, and then accessing the resulting tile coordinates from the tileCoords property of tileSource.

Attribution

This class is a fork of Mapbox / Vladimir Agafonkin's wonderful geojson-vt module.

This directory is forked from Mapbox's https://github.com/mapbox/geojson-vt under ISC License.