Measure distances | UNL Map JS Docs

Click points on a map to create lines that measure distanced using turf.length.
Note
If you want to test this example, edit it in JSFiddle or CodePen and replace the "YOUR-OWN-API-KEY" and "YOUR-OWN-VPM-ID" placeholders with your actual api key and vpm id.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Measure distances</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
<script src="https://unpkg.com/unl-map-js@0.1.5/lib/unl-map-js.js"></script>
<link href="https://unpkg.com/unl-map-js@0.1.5/lib/unl-map-js.css" rel="stylesheet" />
<link
href="https://unpkg.com/maplibre-gl@2.1.9/dist/maplibre-gl.css"
rel="stylesheet"
/>
<style>
	body { margin: 0; padding: 0; }
	#map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>
<style>
.distance-container {
position: absolute;
top: 10px;
left: 10px;
z-index: 1;
}
 
.distance-container > * {
background-color: rgba(0, 0, 0, 0.5);
color: #fff;
font-size: 11px;
line-height: 18px;
display: block;
margin: 0;
padding: 5px 10px;
border-radius: 3px;
}
</style>
 
<div id="map"></div>
<div id="distance" class="distance-container"></div>
 
<script src="https://npmcdn.com/@turf/turf@5.1.6/turf.min.js"></script>
<script>
var map = new UnlSdk.Map({
container: "map",
apiKey: "YOUR-OWN-API-KEY",
vpmId: "YOUR-OWN-VPM-ID",
center: [2.3399, 48.8555],
zoom: 12,
});
 
var distanceContainer = document.getElementById("distance");
 
// GeoJSON object to hold our measurement features
var geojson = {
type: "FeatureCollection",
features: [],
};
 
// Used to draw a line between points
var linestring = {
type: "Feature",
geometry: {
type: "LineString",
coordinates: [],
},
};
 
map.on("load", function () {
map.addSource("geojson", {
type: "geojson",
data: geojson,
});
 
// Add styles to the map
map.addLayer({
id: "measure-points",
type: "circle",
source: "geojson",
paint: {
"circle-radius": 5,
"circle-color": "#000",
},
filter: ["in", "$type", "Point"],
});
map.addLayer({
id: "measure-lines",
type: "line",
source: "geojson",
layout: {
"line-cap": "round",
"line-join": "round",
},
paint: {
"line-color": "#000",
"line-width": 2.5,
},
filter: ["in", "$type", "LineString"],
});
 
map.on("click", function (e) {
var features = map.queryRenderedFeatures(e.point, {
layers: ["measure-points"],
});
 
// Remove the linestring from the group
// So we can redraw it based on the points collection
if (geojson.features.length > 1) geojson.features.pop();
 
// Clear the Distance container to populate it with a new value
distanceContainer.innerHTML = "";
 
// If a feature was clicked, remove it from the map
if (features.length) {
var id = features[0].properties.id;
geojson.features = geojson.features.filter(function (point) {
return point.properties.id !== id;
});
} else {
var point = {
type: "Feature",
geometry: {
type: "Point",
coordinates: [e.lngLat.lng, e.lngLat.lat],
},
properties: {
id: String(new Date().getTime()),
},
};
 
geojson.features.push(point);
}
 
if (geojson.features.length > 1) {
linestring.geometry.coordinates = geojson.features.map(function (
point
) {
return point.geometry.coordinates;
});
 
geojson.features.push(linestring);
 
// Populate the distanceContainer with total distance
var value = document.createElement("pre");
value.textContent =
"Total distance: " + turf.length(linestring).toLocaleString() + "km";
distanceContainer.appendChild(value);
}
 
map.getSource("geojson").setData(geojson);
});
});
 
map.on("mousemove", function (e) {
var features = map.queryRenderedFeatures(e.point, {
layers: ["measure-points"],
});
// UI indicator for clicking/hovering a point on the map
map.getCanvas().style.cursor = features.length ? "pointer" : "crosshair";
});
</script>
 
</body>
</html>