Measure distances | TrackAsia GL JS Docs

Click points on a map to create lines that measure distanced using turf.length.
<!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/trackasia-gl@1.0.5/dist/trackasia-gl.js"></script>
<link href="https://unpkg.com/trackasia-gl@1.0.5/dist/trackasia-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 trackasiagl.Map({
container: 'map',
style: 'https://maps.track-asia.com/styles/v1/streets.json?key=public_key',
center: {"lat":10.762622,"lng":106.660172},
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>