Animate a point along a route

You can utilize the Turf library to create seamless animations of a point moving along the length of a line.

<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Animate a point along a route</title>
<script src="https://cdn.maptiler.com/maptiler-sdk-js/v3.0.1/maptiler-sdk.umd.min.js"></script>
<link href="https://cdn.maptiler.com/maptiler-sdk-js/v3.0.1/maptiler-sdk.css" rel="stylesheet" />
<style>
  body {margin: 0; padding: 0;}
  #map {position: absolute; top: 0; bottom: 0; width: 100%;}
</style>
</head>
<body>
<style>
    .overlay {
        position: absolute;
        top: 10px;
        left: 10px;
    }

    .overlay button {
        font: 600 12px/20px 'Helvetica Neue', Arial, Helvetica, sans-serif;
        background-color: #3386c0;
        color: #fff;
        display: inline-block;
        margin: 0;
        padding: 10px 20px;
        border: none;
        cursor: pointer;
        border-radius: 3px;
    }

    .overlay button:hover {
        background-color: #4ea0da;
    }
</style>
<script src="https://cdn.jsdelivr.net/npm/@turf/turf@7/turf.min.js"></script>

<div id="map"></div>
<div class="overlay">
    <button id="replay">Replay</button>
</div>

<script>
    maptilersdk.config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
    var map = new maptilersdk.Map({
        container: 'map',
        style: maptilersdk.MapStyle.STREETS,
        center: [-96, 37.8],
        zoom: 3
    });

    // San Francisco
    var origin = [-122.414, 37.776];

    // Washington DC
    var destination = [-77.032, 38.913];

    // A simple line from origin to destination.
    var route = {
        'type': 'FeatureCollection',
        'features': [
            {
                'type': 'Feature',
                'geometry': {
                    'type': 'LineString',
                    'coordinates': [origin, destination]
                }
            }
        ]
    };

    // A single point that animates along the route.
    // Coordinates are initially set to origin.
    var point = {
        'type': 'FeatureCollection',
        'features': [
            {
                'type': 'Feature',
                'properties': {},
                'geometry': {
                    'type': 'Point',
                    'coordinates': origin
                }
            }
        ]
    };

    // Calculate the distance in kilometers between route start/end point.
    var lineDistance = turf.length(route.features[0], 'kilometers');

    var arc = [];

    // Number of steps to use in the arc and animation, more steps means
    // a smoother arc and animation, but too many steps will result in a
    // low frame rate
    var steps = 500;

    // Draw an arc between the `origin` & `destination` of the two points
    for (var i = 0; i < lineDistance; i += lineDistance / steps) {
        var segment = turf.along(route.features[0], i, 'kilometers');
        arc.push(segment.geometry.coordinates);
    }

    // Update the route with calculated arc coordinates
    route.features[0].geometry.coordinates = arc;

    // Used to increment the value of the point measurement against the route.
    var counter = 0;

    map.on('load', function () {
        // Add a source and layer displaying a point which will be animated in a circle.
        map.addSource('route', {
            'type': 'geojson',
            'data': route
        });

        map.addSource('point', {
            'type': 'geojson',
            'data': point
        });

        map.addLayer({
            'id': 'route',
            'source': 'route',
            'type': 'line',
            'paint': {
                'line-width': 2,
                'line-color': '#007cbf'
            }
        });

        map.addLayer({
            'id': 'point',
            'source': 'point',
            'type': 'symbol',
            'layout': {
                'icon-image': 'airport',
                'icon-rotate': ['get', 'bearing'],
                'icon-rotation-alignment': 'map',
                'icon-overlap': 'always',
                'icon-ignore-placement': true
            }
        });

        function animate() {
            // Update point geometry to a new position based on counter denoting
            // the index to access the arc.
            point.features[0].geometry.coordinates =
                route.features[0].geometry.coordinates[counter];

            // Calculate the bearing to ensure the icon is rotated to match the route arc
            // The bearing is calculate between the current point and the next point, except
            // at the end of the arc use the previous point and the current point
            point.features[0].properties.bearing = turf.bearing(
                turf.point(
                    route.features[0].geometry.coordinates[
                        counter >= steps ? counter - 1 : counter
                    ]
                ),
                turf.point(
                    route.features[0].geometry.coordinates[
                        counter >= steps ? counter : counter + 1
                    ]
                )
            );

            // Update the source with this new data.
            map.getSource('point').setData(point);

            // Request the next frame of animation so long the end has not been reached.
            if (counter < steps) {
                requestAnimationFrame(animate);
            }

            counter = counter + 1;
        }

        document
            .getElementById('replay')
            .addEventListener('click', function () {
                // Set the coordinates of the original point back to origin
                point.features[0].geometry.coordinates = origin;

                // Update the source layer
                map.getSource('point').setData(point);

                // Reset the counter
                counter = 0;

                // Restart the animation.
                animate(counter);
            });

        // Start the animation.
        animate(counter);
    });
</script>
</body>
</html>