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<title>Display cluster area with Convex Hull - Azure Maps Web SDK Samples</title>
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<meta name="description" content="This sample shows how to display the area of the points contained within a cluster by calculating a convex hull. " />
<meta name="keywords" content="Microsoft maps, map, gis, API, SDK, markers, pins, pushpins, symbols, layer, clustering, superclusterer, convex hull, spatial math, earthquakes, USGS" />
<meta name="author" content="Microsoft Azure Maps" />
<!-- Add references to the Azure Maps Map control JavaScript and CSS files. -->
<link rel="stylesheet" href="" type="text/css" />
<script src=""></script>
<script type='text/javascript'>
var map, datasource, polygonDatasource;
//GeoJSON feed of all earthquakes from the past 30 days. Sourced from the USGS.
var earthquakeFeed = "";
//Find more earthquake data feeds here:
function GetMap() {
//Point the Azure Maps domain to the US Azure Gov Cloud domain.
//Initialize a map instance.
map = new atlas.Map('myMap', {
center: [-97, 39],
zoom: 3,
style: 'grayscale_dark',
view: 'Auto',
//Add authentication details for connecting to Azure Maps.
authOptions: {
//Use Azure Active Directory authentication.
authType: 'anonymous',
clientId: 'c9f2f391-13f1-407b-a4a5-f0a241bacfbf', //Your Azure Active Directory client id for accessing your Azure Maps account.
getToken: function (resolve, reject, map) {
//URL to your authentication service that retrieves an Azure Active Directory Token.
var tokenServiceUrl = '';
fetch(tokenServiceUrl).then(r => r.text()).then(token => resolve(token));
//Alternatively, use an Azure Maps key. Get an Azure Maps key at NOTE: The primary key should be used as the key.
//authType: 'subscriptionKey',
//subscriptionKey: '<Your Azure Maps Key>'
//Wait until the map resources are ready.'ready', function () {
//Create a data source for the point data.
datasource = new atlas.source.DataSource(null, {
//Tell the data source to cluster point data.
cluster: true
//Create a data source for the convex hull polygon. Since this will be updated frequently it is more efficient to seperate this into its own data source.
polygonDatasource = new atlas.source.DataSource();
//Add the data sources to the map.
map.sources.add([polygonDatasource, datasource]);
//Create a symbol layer to render the clusters.
var clusterLayer = new atlas.layer.SymbolLayer(datasource, null, {
iconOptions: {
image: 'marker-red'
textOptions: {
textField: ['get', 'point_count_abbreviated'],
offset: [0, -1.2],
color: "#ffffff",
size: 14
filter: ['has', 'point_count'] //Filter individual points from this layer.
//Add a mouse over event to calculate and display the cluster area using a convex hull.'mouseover', clusterLayer, displayClusterArea);
//Add a mouse leave event to remove the convex hull from the map.'mouseleave', clusterLayer, function () {
//Add a polygon layer and a line layer to display the convex hull.
//Add two symbol layers to the map, one for clusters, one for individual points.
//Create a polygon layer to display the area of the convex hull.
new atlas.layer.PolygonLayer(polygonDatasource),
//Create a line layer to display the outline of the convex hull.
new atlas.layer.LineLayer(polygonDatasource),
//Create a layer to render the individual locations.
new atlas.layer.SymbolLayer(datasource, null, {
filter: ['!', ['has', 'point_count']] //Filter out clustered points from this layer.
//Retrieve a GeoJSON data set and add it to the data source.
function displayClusterArea(e) {
if (e && e.shapes && e.shapes.length > 0 && e.shapes[0].properties.cluster) {
//Get the clustered point from the event.
var cluster = e.shapes[0];
//Get all points in the cluster. Set the offset to 0 and the limit to Infinity to return all points.
datasource.getClusterLeaves(, Infinity, 0).then(function (points) {
if (points.length === 2) {
//When only two points in a cluster. Render a line.
} else {
var hullPolygon = atlas.math.getConvexHull(getPositions(points));
//Overwrite all data in the polygon data source with the newly calculated convex hull polygon.
function getPositions(shapes) {
var pos = [];
if (shapes) {
for (var i = 0; i < shapes.length; i++) {
return pos;
<body onload="GetMap()">
<div id="myMap" style="position:relative;width:100%;min-width:290px;height:600px;"></div>
<fieldset style="width:calc(100% - 30px);min-width:290px;margin-top:10px;">
<legend><h1 style="font-size:16px">Display cluster area with Convex Hull</h1></legend>
This sample shows how to display the area of the points contained within a cluster by calculating a convex hull.