This example uses OpenLayers v10.9.0. The latest is v.
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#### Trajectories Heatmap

heatmap 2 geojson 11 vector 86 trajectory 1 webgl 18

#####

radius size blur size Filter by type of ship:

Demonstrates the use of a heatmap layer with linear geometries.

This example shows linear geometries rendered using a `ol/layer/Heatmap` layer.
Data is AIS maritime traffic around Gothenburg transformed into GeoJSON, taken from this example.

##### main.js

    import Map from 'ol/Map.js';
    import View from 'ol/View.js';
    import GeoJSON from 'ol/format/GeoJSON.js';
    import HeatmapLayer from 'ol/layer/Heatmap.js';
    import TileLayer from 'ol/layer/Tile.js';
    import {fromLonLat} from 'ol/proj.js';
    import StadiaMaps from 'ol/source/StadiaMaps.js';
    import VectorSource from 'ol/source/Vector.js';

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

    const heatmap = new HeatmapLayer({
      source: new VectorSource({
        url: 'data/geojson/ship-trajectories.json',
        format: new GeoJSON(),
        attributions: 'Danish Maritime Authority',
      }),
      blur: ['/', ['var', 'blur'], 2],
      radius: ['/', ['var', 'radius'], 2],
      variables: {
        blur: parseInt(blur.value, 10),
        radius: parseInt(radius.value, 10),
        shipType: 'All',
      },
      filter: [
        'any',
        ['==', ['var', 'shipType'], 'All'],
        ['==', ['var', 'shipType'], ['get', 'ShipType']],
      ],
      weight: () => 0.1,
    });

    const raster = new TileLayer({
      source: new StadiaMaps({
        layer: 'alidade_smooth_dark',
      }),
    });

    const map = new Map({
      layers: [raster, heatmap /*vector*/],
      target: 'map',
      view: new View({
        center: fromLonLat([11.86, 57.67]),
        zoom: 12,
      }),
    });

    blur.addEventListener('input', function () {
      heatmap.updateStyleVariables({blur: parseInt(blur.value, 10)});
    });

    radius.addEventListener('input', function () {
      heatmap.updateStyleVariables({radius: parseInt(radius.value, 10)});
    });

    const shipTypeSelect = document.getElementById('shiptype-filter');
    shipTypeSelect.addEventListener('input', function () {
      heatmap.updateStyleVariables({shipType: shipTypeSelect.value});
      map.render();
    });

##### index.html

    <!DOCTYPE html>
    <html lang="en">
      <head>
        <meta charset="UTF-8">
        <title>Trajectories Heatmap</title>
        <link rel="stylesheet" href="node_modules/ol/ol.css">
        <style>
          .map {
            width: 100%;
            height: 400px;
          }
        </style>
      </head>
      <body>
        <div id="map" class="map"></div>
        <form>
          <label for="radius">radius size</label>
          <input id="radius" type="range" min="1" max="50" step="1" value="5"/>
          <label for="blur">blur size</label>
          <input id="blur" type="range" min="1" max="50" step="1" value="15"/>
          <label for="shiptype-filter">Filter by type of ship:</label>
          <select id="shiptype-filter">
              <option>All</option>
              <option>Passenger</option>
              <option>HSC</option>
              <option>Tanker</option>
              <option>Cargo</option>
              <option>Sailing</option>
              <option>Other</option>
              <option>Tug</option>
              <option>SAR</option>
              <option>Pleasure</option>
              <option>Dredging</option>
              <option>Law enforcement</option>
              <option>Pilot</option>
              <option>Fishing</option>
              <option>Diving</option>
              <option>Spare 2</option>
              <option>Undefined</option>
          </select>
        </form>

        <script type="module" src="main.js"></script>
      </body>
    </html>

##### package.json

    {
      "name": "heatmap-trajectories",
      "dependencies": {
        "ol": "10.9.0"
      },
      "devDependencies": {
        "vite": "^3.2.3"
      },
      "scripts": {
        "start": "vite",
        "build": "vite build"
      }
    }