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Visualizing Data: Mapping Earthquakes

Overview

This tutorial shows you how to visualize data on Google maps. As an example, the maps in this tutorial visualize data about the location of earthquakes and their magnitude. Learn techniques to use with your own data source, and create powerful stories on Google maps like the ones below.

The first 2 frames seen above (from left to right) display maps with basic markers, and sized circles. The last frame displays a heatmap.

Importing your data

This tutorial uses real-time earthquake data from the United States Geological Survey (USGS). The USGS website provides their data in a number of formats, which you can copy to your domain for local access by your application. This tutorial requests JSONP directly from the USGS servers by appending a script tag to the head of the document.

// Create a script tag and set the USGS URL as the source.
        var script = document.createElement('script');

        script.src = 'http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_week.geojsonp';
        document.getElementsByTagName('head')[0].appendChild(script);

Placing basic markers

Now that you have pulled data about the location of earthquakes from the USGS feed into your application, you can display it on the map. This section shows you how to create a map that uses imported data to place a basic marker at the epicenter of every earthquake location.

The section below displays the entire code you need to create the map in this tutorial.

var map;
function initMap() {
  map = new google.maps.Map(document.getElementById('map'), {
    zoom: 2,
    center: new google.maps.LatLng(2.8,-187.3),
    mapTypeId: 'terrain'
  });

  // Create a <script> tag and set the USGS URL as the source.
  var script = document.createElement('script');
  // This example uses a local copy of the GeoJSON stored at
  // http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_week.geojsonp
  script.src = 'https://developers.google.com/maps/documentation/javascript/examples/json/earthquake_GeoJSONP.js';
  document.getElementsByTagName('head')[0].appendChild(script);
}

// Loop through the results array and place a marker for each
// set of coordinates.
window.eqfeed_callback = function(results) {
  for (var i = 0; i < results.features.length; i++) {
    var coords = results.features[i].geometry.coordinates;
    var latLng = new google.maps.LatLng(coords[1],coords[0]);
    var marker = new google.maps.Marker({
      position: latLng,
      map: map
    });
  }
}
<div id="map"></div>
/* Always set the map height explicitly to define the size of the div
 * element that contains the map. */
#map {
  height: 100%;
}
/* Optional: Makes the sample page fill the window. */
html, body {
  height: 100%;
  margin: 0;
  padding: 0;
}
<!-- Replace the value of the key parameter with your own API key. -->
<script defer
src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&callback=initMap">
</script>

Try it yourself

You can experiment with this code in JSFiddle by clicking the <> icon in the top-right corner of the code window.

<!DOCTYPE html>
<html>
  <head>
    <style>
      /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
      #map {
        height: 100%;
      }
      /* Optional: Makes the sample page fill the window. */
      html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <script>
      var map;
      function initMap() {
        map = new google.maps.Map(document.getElementById('map'), {
          zoom: 2,
          center: new google.maps.LatLng(2.8,-187.3),
          mapTypeId: 'terrain'
        });

        // Create a <script> tag and set the USGS URL as the source.
        var script = document.createElement('script');
        // This example uses a local copy of the GeoJSON stored at
        // http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_week.geojsonp
        script.src = 'https://developers.google.com/maps/documentation/javascript/examples/json/earthquake_GeoJSONP.js';
        document.getElementsByTagName('head')[0].appendChild(script);
      }

      // Loop through the results array and place a marker for each
      // set of coordinates.
      window.eqfeed_callback = function(results) {
        for (var i = 0; i < results.features.length; i++) {
          var coords = results.features[i].geometry.coordinates;
          var latLng = new google.maps.LatLng(coords[1],coords[0]);
          var marker = new google.maps.Marker({
            position: latLng,
            map: map
          });
        }
      }
    </script>
    <script defer
    src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap">
    </script>
  </body>
</html>