calc distance from (lng1,lat1) to (lng2,lat2)

gistfile1.js

	function distanceLL(x1, y1, x2, y2)
	{
		var DEG2RAD = Math.PI / 180.0;
		x1 *= DEG2RAD;
		y1 *= DEG2RAD;
		x2 *= DEG2RAD;
		y2 *= DEG2RAD;
		var dx = Math.abs(x2-x1);
		var dy = Math.abs(y2-y1);
		var phi = dy*0.5 + y1;

		var S = Math.sin(phi);
		var M = 6335439.0 / (Math.sqrt( Math.pow( (1- 0.006674*S*S) , 3) ));
		var N = 6378137.0 / Math.sqrt( 1- 0.006674*S*S );

		return Math.sqrt( Math.pow(M*dy, 2) + Math.pow(N*Math.cos(phi)*dx ,2) );
	}