Google maps geolocation get directions

getdirections.js

<script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?key=123&sensor=false&language=el"></script>
<script>
var directionsDisplay;
var directionsService = new google.maps.DirectionsService();

function initialize() {
  directionsDisplay = new google.maps.DirectionsRenderer();
  var mapOptions = {
    zoom: 9,
    mapTypeId: google.maps.MapTypeId.ROADMAP,
    center: new google.maps.LatLng(40.392581, 21.549683)
  };
  var map = new google.maps.Map(document.getElementById('map-canvas'),
      mapOptions);
  directionsDisplay.setMap(map);
  directionsDisplay.setPanel(document.getElementById('directions-panel'));


}

function getLocation(callback) {
	if (navigator.geolocation) {
		navigator.geolocation.getCurrentPosition(function (position) {
			callback({
				lat: position.coords.latitude,
				lon: position.coords.longitude
			});
		},function (error) { 
			alert("Location not found");
		});
	} else {
		alert("Location not found");
	}
}

function getStart(callback) {
	var start = document.getElementById('start').value;
	
	if (start == "my_location") {
		getLocation(function (loc) {
			start = new google.maps.LatLng(loc.lat, loc.lon);
			callback(start);
		});
	} else {
		callback(start);
	}
	
}	

function calcRoute() {
	
	var end = document.getElementById('end').value;

	if (end != "") {
		getStart(function (start) {
			
			var request = {
				origin: start,
				destination: end,
				travelMode: google.maps.TravelMode.DRIVING
			};
			
			directionsService.route(request, function(response, status) {
				if (status == google.maps.DirectionsStatus.OK) {
					directionsDisplay.setDirections(response);
				}
			});
			
		});
	}

}

google.maps.event.addDomListener(window, 'load', initialize);

</script>

select.html

<select id="start" onchange="calcRoute();">
<option value="my_location">Η τοποθεσία μου</option>
<option value="Thessaloniki, Ελλάδα">Θεσσαλονίκη</option>
<option value="Αθήνα, Ελλάδα">Αθήνα</option>
<option value="Πάτρα, Αχαΐα, Ελλάδα">Πάτρα</option>
</select>

<select id="end" onchange="calcRoute();">
<option value="">Επιλέξτε</option>
<option value="Γρεβενά, Ελλάδα">Γρεβενά</option>
<option value="Καστοριά, Ελλάδα">Καστοριά</option>
<option value="Κοζάνη, Ελλάδα">Κοζάνη</option>
<option value="Φλώρινα, Ελλάδα">Φλώρινα</option>
</select>