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Geolocation watchPosition() API

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Description:

The watchPosition method retrieves periodic updates about the current geographic location of the device. The location is expressed as a set of geographic coordinates together with information about heading and speed.

The location information is returned in a Position object. Each update returns a new Position object.

Syntax:

Here is the syntax of this method:

watchPosition(showLocation, ErrorHandler, options);

Parameters:

Here is the detail of parameters:

Return value:

The watchPosition method returns a unique transaction ID (number) associated with the asynchronous call. Use this ID to cancel the watchPosition call and to stop receiving location updates.

Example:

<!DOCTYPE HTML>
<head>
<script type="text/javascript">
var watchID;
var geoLoc;

function showLocation(position) {
  var latitude = position.coords.latitude;
  var longitude = position.coords.longitude;
  alert("Latitude : " + latitude + " Longitude: " + longitude);
}

function errorHandler(err) {
  if(err.code == 1) {
    alert("Error: Access is denied!");
  }else if( err.code == 2) {
    alert("Error: Position is unavailable!");
  }
}
function getLocationUpdate(){

   if(navigator.geolocation){
      // timeout at 60000 milliseconds (60 seconds)
      var options = {timeout:60000};
      geoLoc = navigator.geolocation;
      watchID = geoLoc.watchPosition(showLocation, 
                                     errorHandler,
                                     options);
   }else{
      alert("Sorry, browser does not support geolocation!");
   }
}
</script>
</head>
<html>
<body>
   <form>
     <input type="button" onclick="getLocationUpdate();"  
                             value="Watch Update"/>
   </form>
</body>
</html>

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