JavaScript Maps SDK

Create a heatmap layer

Visualize earthquake frequency by location using a heatmap layer. 


<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>Create a heatmap layer</title>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="stylesheet" href="https://maps-sdk.trimblemaps.com/v4/trimblemaps-4.2.5.css" />
    <script src="https://maps-sdk.trimblemaps.com/v4/trimblemaps-4.2.5.js"></script>
    <style>
      body {
        margin: 0;
        padding: 0;
      }
      html,
      body,
      #map {
        height: 100%;
      }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <script>
      TrimbleMaps.setAPIKey('YOUR_API_KEY_HERE');
      const map = new TrimbleMaps.Map({
        container: 'map',
        style: TrimbleMaps.Common.Style.TERRAIN,
        region: 'ww',
        center: [-120, 50],
        zoom: 2,
      });

      map.on('load', () => {
        // Add a geojson point source.
        // Heatmap layers also work with a vector tile source.
        map.addSource('earthquakes', {
          type: 'geojson',
          data: 'https://developer.trimblemaps.com/maps-sdk/assets/earthquakes.geojson',
        });

        map.addLayer(
          {
            id: 'earthquakes-heat',
            type: 'heatmap',
            source: 'earthquakes',
            maxzoom: 9,
            paint: {
              // Increase the heatmap weight based on frequency and property magnitude
              'heatmap-weight': [
                'interpolate',
                ['linear'],
                ['get', 'mag'],
                0,
                0,
                6,
                1,
              ],
              // Increase the heatmap color weight weight by zoom level
              // heatmap-intensity is a multiplier on top of heatmap-weight
              'heatmap-intensity': [
                'interpolate',
                ['linear'],
                ['zoom'],
                0,
                1,
                9,
                3,
              ],
              // Color ramp for heatmap.  Domain is 0 (low) to 1 (high).
              // Begin color ramp at 0-stop with a 0-transparency color
              // to create a blur-like effect.
              'heatmap-color': [
                'interpolate',
                ['linear'],
                ['heatmap-density'],
                0,
                'rgba(33,102,172,0)',
                0.2,
                'rgb(103,169,207)',
                0.4,
                'rgb(209,229,240)',
                0.6,
                'rgb(253,219,199)',
                0.8,
                'rgb(239,138,98)',
                1,
                'rgb(178,24,43)',
              ],
              // Adjust the heatmap radius by zoom level
              'heatmap-radius': [
                'interpolate',
                ['linear'],
                ['zoom'],
                0,
                2,
                9,
                20,
              ],
              // Transition from heatmap to circle layer by zoom level
              'heatmap-opacity': [
                'interpolate',
                ['linear'],
                ['zoom'],
                7,
                1,
                9,
                0,
              ],
            },
          },
          'labels_waterway'
        );

        map.addLayer(
          {
            id: 'earthquakes-point',
            type: 'circle',
            source: 'earthquakes',
            minzoom: 7,
            paint: {
              // Size circle radius by earthquake magnitude and zoom level
              'circle-radius': [
                'interpolate',
                ['linear'],
                ['zoom'],
                7,
                ['interpolate', ['linear'], ['get', 'mag'], 1, 1, 6, 4],
                16,
                ['interpolate', ['linear'], ['get', 'mag'], 1, 5, 6, 50],
              ],
              // Color circle by earthquake magnitude
              'circle-color': [
                'interpolate',
                ['linear'],
                ['get', 'mag'],
                1,
                'rgba(33,102,172,0)',
                2,
                'rgb(103,169,207)',
                3,
                'rgb(209,229,240)',
                4,
                'rgb(253,219,199)',
                5,
                'rgb(239,138,98)',
                6,
                'rgb(178,24,43)',
              ],
              'circle-stroke-color': 'white',
              'circle-stroke-width': 1,
              // Transition from heatmap to circle layer by zoom level
              'circle-opacity': [
                'interpolate',
                ['linear'],
                ['zoom'],
                7,
                0,
                8,
                1,
              ],
            },
          },
          'labels_waterway'
        );
      });
    </script>
  </body>
</html>
Last updated July 2, 2025.