text: var map, marker;
  function initMap() {
  	map = new google.maps.Map(document.getElementById('map'), {
  		center: { lat: -34.397, lng: 150.644 },
  		zoom: 18,
  	});
  
  	var symbol = {
  		// url: 'car.png',
  		path: google.maps.SymbolPath.FORWARD_CLOSED_ARROW,
  		fillColor: 'red',
  		fillOpacity: 0.9,
  		strokeWeight: 6,
  		scale: 8,
  		rotation: 0,
  	};
  
  	marker = new google.maps.Marker({
  		icon: symbol,
  		map,
  	});
  }
  
  // mqtt
  var client = mqtt.connect('ws://157.230.113.66:3000');
  
  client.subscribe('LOCATION');
  
  client.on('connect', function() {
  	console.log('connected!');
  });
  
  client.on('message', function(topic, message) {
  	console.log(topic, ' : ', message.toString());
  	switch (topic) {
  		case 'LOCATION':
  			updateMap(message);
  			break;
  		default:
  			break;
  	}
  });
  
  function updateMap(message) {
  	[lat, lng, altitude, speed, course] = message.toString().split(',');
  
  	let position = { lat: parseFloat(lat), lng: parseFloat(lng) };
  	marker.setPosition(position);
  	marker.setIcon({ ...marker.getIcon(), rotation: parseInt(course) });
  	map.setCenter(position);
  
  	document.getElementById('km').innerHTML = speed;
  	document.getElementById('msl').innerHTML = altitude;
  }
  