You're all set!

To start developing, please head over to our developer documentation.

Activate the Google Maps JavaScript API

To get you started we'll guide you through the Google Developers Console to do a few things first:

  1. Create or choose a project
  2. Activate the Google Maps JavaScript API and related services
  3. Create appropriate keys
Continue

Adding a Custom Overlay

Read the documentation or view this example full screen.

// This example creates a custom overlay called USGSOverlay, containing
// a U.S. Geological Survey (USGS) image of the relevant area on the map.

// Set the custom overlay object's prototype to a new instance
// of OverlayView. In effect, this will subclass the overlay class therefore
// it's simpler to load the API synchronously, using
// google.maps.event.addDomListener().
// Note that we set the prototype to an instance, rather than the
// parent class itself, because we do not wish to modify the parent class.

var overlay;
USGSOverlay.prototype = new google.maps.OverlayView();

// Initialize the map and the custom overlay.

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 11,
    center: {lat: 62.323907, lng: -150.109291},
    mapTypeId: 'satellite'
  });

  var bounds = new google.maps.LatLngBounds(
      new google.maps.LatLng(62.281819, -150.287132),
      new google.maps.LatLng(62.400471, -150.005608));

  // The photograph is courtesy of the U.S. Geological Survey.
  var srcImage = 'https://developers.google.com/maps/documentation/' +
      'javascript/examples/full/images/talkeetna.png';

  // The custom USGSOverlay object contains the USGS image,
  // the bounds of the image, and a reference to the map.
  overlay = new USGSOverlay(bounds, srcImage, map);
}

/** @constructor */
function USGSOverlay(bounds, image, map) {

  // Initialize all properties.
  this.bounds_ = bounds;
  this.image_ = image;
  this.map_ = map;

  // Define a property to hold the image's div. We'll
  // actually create this div upon receipt of the onAdd()
  // method so we'll leave it null for now.
  this.div_ = null;

  // Explicitly call setMap on this overlay.
  this.setMap(map);
}

/**
 * onAdd is called when the map's panes are ready and the overlay has been
 * added to the map.
 */
USGSOverlay.prototype.onAdd = function() {

  var div = document.createElement('div');
  div.style.borderStyle = 'none';
  div.style.borderWidth = '0px';
  div.style.position = 'absolute';

  // Create the img element and attach it to the div.
  var img = document.createElement('img');
  img.src = this.image_;
  img.style.width = '100%';
  img.style.height = '100%';
  img.style.position = 'absolute';
  div.appendChild(img);

  this.div_ = div;

  // Add the element to the "overlayLayer" pane.
  var panes = this.getPanes();
  panes.overlayLayer.appendChild(div);
};

USGSOverlay.prototype.draw = function() {

  // We use the south-west and north-east
  // coordinates of the overlay to peg it to the correct position and size.
  // To do this, we need to retrieve the projection from the overlay.
  var overlayProjection = this.getProjection();

  // Retrieve the south-west and north-east coordinates of this overlay
  // in LatLngs and convert them to pixel coordinates.
  // We'll use these coordinates to resize the div.
  var sw = overlayProjection.fromLatLngToDivPixel(this.bounds_.getSouthWest());
  var ne = overlayProjection.fromLatLngToDivPixel(this.bounds_.getNorthEast());

  // Resize the image's div to fit the indicated dimensions.
  var div = this.div_;
  div.style.left = sw.x + 'px';
  div.style.top = ne.y + 'px';
  div.style.width = (ne.x - sw.x) + 'px';
  div.style.height = (sw.y - ne.y) + 'px';
};

// The onRemove() method will be called automatically from the API if
// we ever set the overlay's map property to 'null'.
USGSOverlay.prototype.onRemove = function() {
  this.div_.parentNode.removeChild(this.div_);
  this.div_ = null;
};

google.maps.event.addDomListener(window, 'load', initMap);
<div id="map"></div>
html, body {
  height: 100%;
  margin: 0;
  padding: 0;
}
#map {
  height: 100%;
}
<!-- Replace the value of the key parameter with your own API key. -->
<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>

Try it yourself

Hover at top right of the code block to copy the code or open it in JSFiddle.

<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <title>Adding a Custom Overlay</title>
    <style>
      html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
      #map {
        height: 100%;
      }
    </style>
    <script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY"></script>
    <script>
      // This example creates a custom overlay called USGSOverlay, containing
      // a U.S. Geological Survey (USGS) image of the relevant area on the map.

      // Set the custom overlay object's prototype to a new instance
      // of OverlayView. In effect, this will subclass the overlay class therefore
      // it's simpler to load the API synchronously, using
      // google.maps.event.addDomListener().
      // Note that we set the prototype to an instance, rather than the
      // parent class itself, because we do not wish to modify the parent class.

      var overlay;
      USGSOverlay.prototype = new google.maps.OverlayView();

      // Initialize the map and the custom overlay.

      function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {
          zoom: 11,
          center: {lat: 62.323907, lng: -150.109291},
          mapTypeId: 'satellite'
        });

        var bounds = new google.maps.LatLngBounds(
            new google.maps.LatLng(62.281819, -150.287132),
            new google.maps.LatLng(62.400471, -150.005608));

        // The photograph is courtesy of the U.S. Geological Survey.
        var srcImage = 'https://developers.google.com/maps/documentation/' +
            'javascript/examples/full/images/talkeetna.png';

        // The custom USGSOverlay object contains the USGS image,
        // the bounds of the image, and a reference to the map.
        overlay = new USGSOverlay(bounds, srcImage, map);
      }

      /** @constructor */
      function USGSOverlay(bounds, image, map) {

        // Initialize all properties.
        this.bounds_ = bounds;
        this.image_ = image;
        this.map_ = map;

        // Define a property to hold the image's div. We'll
        // actually create this div upon receipt of the onAdd()
        // method so we'll leave it null for now.
        this.div_ = null;

        // Explicitly call setMap on this overlay.
        this.setMap(map);
      }

      /**
       * onAdd is called when the map's panes are ready and the overlay has been
       * added to the map.
       */
      USGSOverlay.prototype.onAdd = function() {

        var div = document.createElement('div');
        div.style.borderStyle = 'none';
        div.style.borderWidth = '0px';
        div.style.position = 'absolute';

        // Create the img element and attach it to the div.
        var img = document.createElement('img');
        img.src = this.image_;
        img.style.width = '100%';
        img.style.height = '100%';
        img.style.position = 'absolute';
        div.appendChild(img);

        this.div_ = div;

        // Add the element to the "overlayLayer" pane.
        var panes = this.getPanes();
        panes.overlayLayer.appendChild(div);
      };

      USGSOverlay.prototype.draw = function() {

        // We use the south-west and north-east
        // coordinates of the overlay to peg it to the correct position and size.
        // To do this, we need to retrieve the projection from the overlay.
        var overlayProjection = this.getProjection();

        // Retrieve the south-west and north-east coordinates of this overlay
        // in LatLngs and convert them to pixel coordinates.
        // We'll use these coordinates to resize the div.
        var sw = overlayProjection.fromLatLngToDivPixel(this.bounds_.getSouthWest());
        var ne = overlayProjection.fromLatLngToDivPixel(this.bounds_.getNorthEast());

        // Resize the image's div to fit the indicated dimensions.
        var div = this.div_;
        div.style.left = sw.x + 'px';
        div.style.top = ne.y + 'px';
        div.style.width = (ne.x - sw.x) + 'px';
        div.style.height = (sw.y - ne.y) + 'px';
      };

      // The onRemove() method will be called automatically from the API if
      // we ever set the overlay's map property to 'null'.
      USGSOverlay.prototype.onRemove = function() {
        this.div_.parentNode.removeChild(this.div_);
        this.div_ = null;
      };

      google.maps.event.addDomListener(window, 'load', initMap);
    </script>
  </head>
  <body>
    <div id="map"></div>
  </body>
</html>

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