Inset Overview Map

Maintaining a geographical frame of reference

An inset map is a smaller map to help the user maintain a geographical frame of reference. The overview map is synchronized with the bounds_changed event on the main map.

TypeScript

const OVERVIEW_DIFFERENCE = 5;
const OVERVIEW_MIN_ZOOM = 3;
const OVERVIEW_MAX_ZOOM = 10;

function initMap(): void {
  const mapOptions = {
    center: { lat: 50, lng: 8 },
    zoom: 7,
  };

  // instantiate the primary map
  map = new google.maps.Map(document.getElementById("map") as HTMLElement, {
    ...mapOptions,
  });

  // instantiate the overview map without controls
  overview = new google.maps.Map(
    document.getElementById("overview") as HTMLElement,
    {
      ...mapOptions,
      disableDefaultUI: true,
      gestureHandling: "none",
      zoomControl: false,
    }
  );

  function clamp(num, min, max) {
    return Math.min(Math.max(num, min), max);
  }

  map.addListener("bounds_changed", () => {
    overview.setCenter(map.getCenter()!);
    overview.setZoom(
      clamp(
        map.getZoom()! - OVERVIEW_DIFFERENCE,
        OVERVIEW_MIN_ZOOM,
        OVERVIEW_MAX_ZOOM
      )
    );
  });
}
index.ts

JavaScript

let map, overview;
const OVERVIEW_DIFFERENCE = 5;
const OVERVIEW_MIN_ZOOM = 3;
const OVERVIEW_MAX_ZOOM = 10;

function initMap() {
  const mapOptions = {
    center: { lat: 50, lng: 8 },
    zoom: 7,
  };
  // instantiate the primary map
  map = new google.maps.Map(document.getElementById("map"), {
    ...mapOptions,
  });
  // instantiate the overview map without controls
  overview = new google.maps.Map(document.getElementById("overview"), {
    ...mapOptions,
    disableDefaultUI: true,
    gestureHandling: "none",
    zoomControl: false,
  });

  function clamp(num, min, max) {
    return Math.min(Math.max(num, min), max);
  }
  map.addListener("bounds_changed", () => {
    overview.setCenter(map.getCenter());
    overview.setZoom(
      clamp(
        map.getZoom() - OVERVIEW_DIFFERENCE,
        OVERVIEW_MIN_ZOOM,
        OVERVIEW_MAX_ZOOM
      )
    );
  });
}

index.js

CSS

/* 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;
}

#container,
#map {
  height: 100%;
  width: 100%;
}

#map {
  position: relative;
}

#overview {
  position: absolute;
  left: 40px;
  height: 175px;
  width: 175px;
  bottom: 50px;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
}

style.css

HTML

<!DOCTYPE html>
<html>
  <head>
    <title>Inset Overview Map</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script src="./index.js"></script>
  </head>
  <body>
    <div id="container">
      <div id="map"></div>
      <div id="overview"></div>
    </div>

    <!-- Async script executes immediately and must be after any DOM elements used in callback. -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap&libraries=&v=weekly"
      async
    ></script>
  </body>
</html>
sample.html

All

<!DOCTYPE html>
<html>
  <head>
    <title>Inset Overview Map</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <style type="text/css">
      /* 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;
      }

      #container,
      #map {
        height: 100%;
        width: 100%;
      }

      #map {
        position: relative;
      }

      #overview {
        position: absolute;
        left: 40px;
        height: 175px;
        width: 175px;
        bottom: 50px;
        box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
      }
    </style>
    <script>
      let map, overview;
      const OVERVIEW_DIFFERENCE = 5;
      const OVERVIEW_MIN_ZOOM = 3;
      const OVERVIEW_MAX_ZOOM = 10;

      function initMap() {
        const mapOptions = {
          center: { lat: 50, lng: 8 },
          zoom: 7,
        };
        // instantiate the primary map
        map = new google.maps.Map(document.getElementById("map"), {
          ...mapOptions,
        });
        // instantiate the overview map without controls
        overview = new google.maps.Map(document.getElementById("overview"), {
          ...mapOptions,
          disableDefaultUI: true,
          gestureHandling: "none",
          zoomControl: false,
        });

        function clamp(num, min, max) {
          return Math.min(Math.max(num, min), max);
        }
        map.addListener("bounds_changed", () => {
          overview.setCenter(map.getCenter());
          overview.setZoom(
            clamp(
              map.getZoom() - OVERVIEW_DIFFERENCE,
              OVERVIEW_MIN_ZOOM,
              OVERVIEW_MAX_ZOOM
            )
          );
        });
      }
    </script>
  </head>
  <body>
    <div id="container">
      <div id="map"></div>
      <div id="overview"></div>
    </div>

    <!-- Async script executes immediately and must be after any DOM elements used in callback. -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap&libraries=&v=weekly"
      async
    ></script>
  </body>
</html>

inline.html
let map, overview; const OVERVIEW_DIFFERENCE = 5; const OVERVIEW_MIN_ZOOM = 3; const OVERVIEW_MAX_ZOOM = 10; function initMap() { const mapOptions = { center: { lat: 50, lng: 8 }, zoom: 7, }; // instantiate the primary map map = new google.maps.Map(document.getElementById("map"), { ...mapOptions, }); // instantiate the overview map without controls overview = new google.maps.Map(document.getElementById("overview"), { ...mapOptions, disableDefaultUI: true, gestureHandling: "none", zoomControl: false, }); function clamp(num, min, max) { return Math.min(Math.max(num, min), max); } map.addListener("bounds_changed", () => { overview.setCenter(map.getCenter()); overview.setZoom( clamp( map.getZoom() - OVERVIEW_DIFFERENCE, OVERVIEW_MIN_ZOOM, OVERVIEW_MAX_ZOOM ) ); }); }
/* 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; } #container, #map { height: 100%; width: 100%; } #map { position: relative; } #overview { position: absolute; left: 40px; height: 175px; width: 175px; bottom: 50px; box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3); }
<!DOCTYPE html> <html> <head> <title>Inset Overview Map</title> <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script> <!-- jsFiddle will insert css and js --> </head> <body> <div id="container"> <div id="map"></div> <div id="overview"></div> </div> <!-- Async script executes immediately and must be after any DOM elements used in callback. --> <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&libraries=&v=weekly" async ></script> </body> </html>