Google Maps Elevation Service

Question

I have this function which is invoked upon clicking a button. The function creates a marker at a predefined position. I then use the elevation service for the given point. When I click the button, the alert message (I've put it there for diagnostics) displays 'undefined', and then the marker appears (in fact the marker should appear before the alert box!). I've tried my best to identify the source of the problem but in vain. Can anyone help me please? Thanks.

  function buttonClicked () {
     addNode(someLat, someLong);
     alert(getElev(markers[0]));
  }

  function addNode(lat, lng) {
      var LatLng = new google.maps.LatLng(lat, lng);
      var marker = new google.maps.Marker({
         position: LatLng,
      });
      marker.setMap(map);
      markers.push(marker);
  }

  function getElev (marker) {
      var ht = 0;
      var locations = [];
      var clickedLocation = marker.getPosition();
      locations.push(clickedLocation);
      var positionalRequest = {
        'locations': locations
      }

      elevator.getElevationForLocations(positionalRequest, function (results, status) {
          if (status == google.maps.ElevationStatus.OK && results[0]) 
               ht = results[0].elevation;
      });
      return ht;
  }

score 1 · Accepted Answer · answered Apr 01 '13 at 23:13

1

Add the alert here and it should work. The function inside getElevationForLocations does not occur within getElev, but is called asynchronously. so ht is not set within getElev.

  elevator.getElevationForLocations(positionalRequest, function (results, status) {
      if (status == google.maps.ElevationStatus.OK && results[0]){
           ht = results[0].elevation;
           alert(ht);
      }
  });

answered Apr 01 '13 at 23:13

Fred

222
2
6

I was wondering, though. Is there a way that we wait for the asynchrnous call to complete before we leave getElevationForLocations? – Imran Apr 02 '13 at 03:25

score -1 · Answer 2 · answered Dec 09 '15 at 22:04

altitude = 0; // Declared with out "var" make it superglobal 
function buttonClicked () {
 addNode(someLat, someLong);
 alert(getAltitude());
}

function addNode(lat, lng) {
  var LatLng = new google.maps.LatLng(lat, lng);
  var marker = new google.maps.Marker({
     position: LatLng,
  });
  marker.setMap(map);
  markers.push(marker);
}

function getElev (marker) {
  var locations = [];
  var clickedLocation = marker.getPosition();
  locations.push(clickedLocation);
  var positionalRequest = {
    'locations': locations
  }

  elevator.getElevationForLocations(positionalRequest, function (results, status) {
      if (status == google.maps.ElevationStatus.OK && results[0]) 
           setAltitude(results[0].elevation);
  });
}

//getters and setters for altitude 
function setAltitude(a){
    altitude = a;
}
function getAltitude(){
    return altitude;
}

You really should explain why this solves the OP's problem. – Nathaniel Ford Dec 09 '15 at 22:42 — Nathaniel Ford, Dec 09 '15 at 22:42

Google Maps Elevation Service

2 Answers2