Earthquakes Heatmap

Demonstrates the use of a heatmap layer.

This example parses a KML file and renders the features as a ol/layer/Heatmap layer.

index.html<!DOCTYPE html>
<html lang="en">
    <title>Earthquakes Heatmap</title>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
      .map {
        width: 100%;
    <div id="map" class="map"></div>
      <label>radius size</label>
      <input id="radius" type="range" min="1" max="50" step="1" value="5"/>
      <label>blur size</label>
      <input id="blur" type="range" min="1" max="50" step="1" value="15"/>
    <script src="index.js"></script>
index.jsimport 'ol/ol.css';
import Map from 'ol/Map';
import View from 'ol/View';
import KML from 'ol/format/KML';
import {Heatmap as HeatmapLayer, Tile as TileLayer} from 'ol/layer';
import Stamen from 'ol/source/Stamen';
import VectorSource from 'ol/source/Vector';

var blur = document.getElementById('blur');
var radius = document.getElementById('radius');

var vector = new HeatmapLayer({
  source: new VectorSource({
    url: 'data/kml/2012_Earthquakes_Mag5.kml',
    format: new KML({
      extractStyles: false
  blur: parseInt(blur.value, 10),
  radius: parseInt(radius.value, 10),
  weight: function(feature) {
    // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
    // standards-violating <magnitude> tag in each Placemark.  We extract it from
    // the Placemark's name instead.
    var name = feature.get('name');
    var magnitude = parseFloat(name.substr(2));
    return magnitude - 5;

var raster = new TileLayer({
  source: new Stamen({
    layer: 'toner'

new Map({
  layers: [raster, vector],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2

var blurHandler = function() {
  vector.setBlur(parseInt(blur.value, 10));
blur.addEventListener('input', blurHandler);
blur.addEventListener('change', blurHandler);

var radiusHandler = function() {
  vector.setRadius(parseInt(radius.value, 10));
radius.addEventListener('input', radiusHandler);
radius.addEventListener('change', radiusHandler);
  "name": "heatmap-earthquakes",
  "dependencies": {
    "ol": "6.1.1"
  "devDependencies": {
    "parcel": "1.11.0"
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --experimental-scope-hoisting --public-url . index.html"