function calcRoute() {
  var start = document.getElementById("start").value;
  var end = document.getElementById("end").value;
  var request = {
      origin:start,
      destination:end,
      travelMode: google.maps.DirectionsTravelMode.DRIVING
  };
  directionsService.route(request, function(response, status) {
    if (status == google.maps.DirectionsStatus.OK) {
      directionsDisplay.setDirections(response);
      var route = directionsDisplay.directions.routes[0]
      var request = { 'path' : route.overview_path , 'samples' : Math.min(Math.floor(route.legs[0].distance.value / 500),1024) }
      elevationService.getElevationAlongPath(request, function(result, status) {
        elevationData = result;
      })
    }
  });
}