private Double distance(double lat1, double lon1, double lat2, double lon2) {
	    double theta = lon1 - lon2;
	    double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) +   Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
	    dist = Math.acos(dist);
	    dist = rad2deg(dist);
	    dist = dist * 60;
	    dist = dist * 1852;
	    return (dist);
	}

	private double deg2rad(double deg) {
	    return (deg * Math.PI / 180.0);
	}

	private double rad2deg(double rad) {
	    return (rad * 180.0 / Math.PI);
	}