javascript - polyline snap to road using google maps api v3

Question

In google maps api v2 it was easy,

var map = new GMap2(document.getElementById("map"));
    map.setCenter(new GLatLng(53.7877, -2.9832),13)
//    map.addControl(new GLargeMapControl());
//    map.addControl(new GMapTypeControl());
    var dirn = new GDirections();

//      var firstpoint = true;
    var gmarkers = [];
    var gpolys = [];
    var dist = 0;

// == When the user clicks on a the map, get directiobns from that point to itself ==

gmarkers.push(new google.maps.LatLng(53.7877, -2.9832));
gmarkers.push(new google.maps.LatLng(53.9007, -2.9832));
gmarkers.push(new GLatLng(53.600, -2.700));



for (var i = 0; i < gmarkers.length-1; i++) {
    console.log(gmarkers[i]);
                dirn.loadFromWaypoints([gmarkers[i].toUrlValue(6),gmarkers[i+1].toUrlValue(6)],{getPolyline:true});

}


// == when the load event completes, plot the point on the street ==
    GEvent.addListener(dirn,"load", function() {
// snap to last vertex in the polyline
        var n = dirn.getPolyline().getVertexCount();
            map.addOverlay(dirn.getPolyline());
            gpolys.push(dirn.getPolyline());
            dist += dirn.getPolyline().getDistance();
            document.getElementById("distance").innerHTML="Path length: "+(dist/1000).toFixed(2)+" km. "+(dist/1609.344).toFixed(2)+" miles.";
           });
    GEvent.addListener(dirn,"error", function() {
        GLog.write("Failed: "+dirn.getStatus().code);
    });
console.log(dirn);

In google api V3 this way simple doesnt work. There is something like directions service but I dont have any idea how I can draw polyline through my points and polyline will be snaped to road.

Answer 1

You were on the right track with the directions service. Here's sample code:

var map, path = new google.maps.MVCArray(),
    service = new google.maps.DirectionsService(), poly;

function Init() {
  var myOptions = {
    zoom: 17,
    center: new google.maps.LatLng(37.2008385157313, -93.2812106609344),
    mapTypeId: google.maps.MapTypeId.HYBRID,
    mapTypeControlOptions: {
      mapTypeIds: [google.maps.MapTypeId.ROADMAP, google.maps.MapTypeId.HYBRID,
          google.maps.MapTypeId.SATELLITE]
    },
    disableDoubleClickZoom: true,
    scrollwheel: false,
    draggableCursor: "crosshair"
  }

  map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
  poly = new google.maps.Polyline({ map: map });
  google.maps.event.addListener(map, "click", function(evt) {
    if (path.getLength() === 0) {
      path.push(evt.latLng);
      poly.setPath(path);
    } else {
      service.route({
        origin: path.getAt(path.getLength() - 1),
        destination: evt.latLng,
        travelMode: google.maps.DirectionsTravelMode.DRIVING
      }, function(result, status) {
        if (status == google.maps.DirectionsStatus.OK) {
          for (var i = 0, len = result.routes[0].overview_path.length;
              i < len; i++) {
            path.push(result.routes[0].overview_path[i]);
          }
        }
      });
    }
  });
}

Also, see my working example: http://people.missouristate.edu/chadkillingsworth/mapsexamples/snaptoroad.htm