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Inset Overview Map

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Page Summary

This sample demonstrates how to create an inset map, providing a smaller overview map synchronized with a main map for better user orientation.
The overview map automatically adjusts its center and zoom level based on the main map's changes, using a predefined zoom difference and limits.
The sample includes code in TypeScript, JavaScript, CSS, and HTML, showcasing the implementation of the inset map functionality.
The overview map is positioned and styled using CSS to appear as an inset element within the main map container.
Users can interact with the main map, while the overview map passively reflects those changes, offering a broader geographical context.

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.

[フレーム]

TypeScript

constOVERVIEW_DIFFERENCE=5;
constOVERVIEW_MIN_ZOOM=3;
constOVERVIEW_MAX_ZOOM=10;
functioninitMap():void{
constmapOptions={
center:{lat:50,lng:8},
zoom:7,
};
// instantiate the primary map
map=newgoogle.maps.Map(document.getElementById("map")asHTMLElement,{
...mapOptions,
});
// instantiate the overview map without controls
overview=newgoogle.maps.Map(
document.getElementById("overview")asHTMLElement,
{
...mapOptions,
disableDefaultUI:true,
gestureHandling:"none",
zoomControl:false,
}
);
functionclamp(num,min,max){
returnMath.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
)
);
});
}
declareglobal{
interfaceWindow{
initMap:()=>void;
}
}
window.initMap=initMap;index.ts

JavaScript

constOVERVIEW_DIFFERENCE=5;
constOVERVIEW_MIN_ZOOM=3;
constOVERVIEW_MAX_ZOOM=10;
functioninitMap(){
constmapOptions={
center:{lat:50,lng:8},
zoom:7,
};
// instantiate the primary map
map=newgoogle.maps.Map(document.getElementById("map"),{
...mapOptions,
});
// instantiate the overview map without controls
overview=newgoogle.maps.Map(document.getElementById("overview"),{
...mapOptions,
disableDefaultUI:true,
gestureHandling:"none",
zoomControl:false,
});
functionclamp(num,min,max){
returnMath.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;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:02px6pxrgba(0,0,0,0.3);
}
style.css

HTML

<html>
 <head>
 <title>Inset Overview Map</title>
 <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>index.html

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.

gitclone-bsample-inset-maphttps://github.com/googlemaps/js-samples.git
cdjs-samples
npmi
npmstart

Other samples can be tried by switching to any branch beginning with sample-SAMPLE_NAME.

gitcheckoutsample-SAMPLE_NAME
npmi
npmstart