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
)
);
});
}
declare global {
interface Window {
initMap: () => void;
}
}
window.initMap = initMap;
JavaScript
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,
),
);
});
}
window.initMap = initMap;
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);
}
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 type="module" src="./index.js"></script>
</head>
<body>
<div id="container">
<div id="map"></div>
<div id="overview"></div>
</div>
<!--
The `defer` attribute causes the script to execute after the full HTML
document has been parsed. For non-blocking uses, avoiding race conditions,
and consistent behavior across browsers, consider loading using Promises. See
https://developers.google.com/maps/documentation/javascript/load-maps-js-api
for more information.
-->
<script
src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&v=weekly"
defer
></script>
</body>
</html>
Try Sample
Clone Sample
Git and Node.js are required to run this sample locally. Follow these
instructions
to install Node.js and NPM. The following commands clone, install dependencies and start the sample application.
git clone -b sample-inset-map https://github.com/googlemaps/js-samples.git
cd js-samples
npm i
npm start
Other samples can be tried by switching to any branch beginning with
sample-
SAMPLE_NAME
.
git checkout sample-
SAMPLE_NAME
npm i
npm start