Google Directions API return different waypoint_order and legs

Question

I'm developing a system to trace route using Google Maps API. I have the points of origin and destination and between these points there are some waypoints. By tracing the route Google returns me the best route and mark these points on the map. We display the route data in a div. My function that calculates the route, the part that returns the data looks like this:

directionsService.route(request, $.proxy(function(response, status){
  if (status == google.maps.DirectionsStatus.OK) {
      directionsDisplay.setDirections(response);
      var orders = response.routes[0].waypoint_order; 
      var route = response.routes[0];
      var total_distance = 0;
      var displayRoute = $('#detail-route');


      for (i = 0; i < route.legs.length; i++){

         var routeSegment = i + 1,
         from_address = route.legs[i].start_address.split(','),
         to_address = route.legs[i].end_address.split(',');
         total_distance += Math.floor(route.legs[i].distance.value / 1000);

         displayRoute.append('<b>Trecho ' + routeSegment + ': </b><br/>');
         displayRoute.append('<b>Saindo de: </b>' + from_address[0] + '<br/>');
         displayRoute.append('<b>Indo para: </b>' + to_address[0] + '<br/>');
         displayRoute.append('<b>Distância: </b>' + route.legs[i].distance.text);
      }

  displayRoute.prepend('total:' + this.format(total_distance) + ' km' + '<br/><br/>');

function format() is my function for format km..

The problem is that, on some routes, the waypoint_order shows a different order than the one in legs. For example:

For a given route, the route.legs[i] returns order: 'waypoint 0, waypoint 1, waypoint 3, waypoint 2', but the waypoint_orderattribute returns [3, 0, 2, 1, 3]

Is this the expected behavior, or am i missing something here?

Answer 1

Is an expected behaivour since:

If optimizeWaypoints was set to true, this field will contain the re-ordered permutation of the input waypoints. For example, if the input was: Origin: Los Angeles
Waypoints: Dallas, Bangor, Phoenix Destination: New York and the optimized output was ordered as follows: Origin: Los Angeles Waypoints: Phoenix, Dallas, Bangor Destination: New York then this field will be an Array containing the values [2, 0, 1]. Note that the numbering of waypoints is zero-based. If any of the input waypoints has stopover set to false, this field will be empty, since route optimization is not available for such queries.

As stated here: DirectionsResult

The waypoint_order is the optimized order

Answer 2

Yes as @sabotero point out, it is an expected behaviour, but there is nothing wrong or strange about that.

When optimizeWaypoints is true, google map try to find the best order of waypoints so that the distance be minimal. For example you can add four locations : Athens-NewYork-London-Los Angeles the google map will find that it is better to go first to London and after to New York. So will return in the array route.legs Athens-London-NewYork-Los Angeles and in waypoint_order will return [1, 0](is only two because is without origin and destination) to inform you that the original order of locations have change. That means that in the first position(waypoint_order[0]) will be the second(returns 1) location who is London and in the second position(waypoint_order[1]) will be the first location(returns 0) who is New York.

Note here that the origin and destination never change position, you always start from the origin you put and you end up in a destination you put. Thats why in waypoint_order is not appear the origin and the destination . So if you have same markers before the request and want to change the order you must exclude the origin and the destination when you reorder, this two will be in the same position.

Now if you want just to draw the markers from the request, don't use waypoint but route legs.

I had made an example, you can enable or disable the optimize with a checkbox and you can see that always the labels of markers come out with the right order: http://jsfiddle.net/TomKarachristos/03wtc6jv/

  var marker = new google.maps.Marker({ //first,
    position: route.legs[0].start_location,
    map: map,
    label: (0).toString()
  });
  for (var i = 1; i < route.legs.length; i++) {
    var marker = new google.maps.Marker({
    position: route.legs[i].start_location,
    map: map,
    label: i.toString()
    });
  }
  var marker = new google.maps.Marker({ //last one
   position: route.legs[route.legs.length - 1].end_location,
   map: map,
   label: route.legs.length.toString()
  });