Ryan Caillouet’s Flash Blog

function getLatLngDistance($lat1:Number, $lng1:Number, $lat2:Number, $lng2:Number, $miles:Boolean=true):Number{
		var pi80:Number = Math.PI/180;
		$lat1 *= pi80;
	      	$lng1 *= pi80;
	      	$lat2 *= pi80;
	      	$lng2 *= pi80;
 
	      	var earthRadius:Number = 6372.797; // mean radius of Earth in km
	      	var dlat:Number = $lat2-$lat1;
	      	var dlng:Number = $lng2-$lng1;
	      	var a:Number = Math.sin(dlat / 2) * Math.sin(dlat / 2) + Math.cos($lat1) * Math.cos($lat2) * Math.sin(dlng / 2) * Math.sin(dlng / 2);
	      	var c:Number = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
	      	var km:Number = earthRadius*c;
     	 	return ($miles ? (km * 0.621371192) : km);
}